SCREENING OF AGRO-PHYSIOLOGICAL TRAITS 
FOR THERMOTOLERANCE IN WHEAT 
(Triticum aestivum L.)

Thesis

Submitted to the Punjab Agricultural University
in partial fulfilment of the requirements
for the degree of

MASTER OF SCIENCE
in
BOTANY 
(Minor subject :  Biochemistry)

By

Amandeep Kaur 
(L-2006-BS-130-M)

Department of Botany
College of Basic Sciences and Humanities
PUNJAB AGRICULTURAL UNIVERSITY
LUDHIANA – 141 004  

2008
CERTIFICATE  I

	This is to certify that the thesis entitled, "Screening of Agro-Physiological Traits for Thermotolerance in Wheat (Triticum aestivum L.)" submitted for the degree of Master of Science, in the subject of Botany (Minor subject: Biochemistry) of Punjab Agricultural University, Ludhiana, is a bonafide research work carried out by Amandeep Kaur (L-2006-BS-130-M) under my supervision and that no part of this thesis has been submitted for any other degree.
	The assistance and help received during the course of investigation have been fully acknowledged.

______________________
Major Advisor
(Dr. D.S. Gill)
Senior Plant Physiologist
Department of Botany
Punjab Agricultural University
Ludhiana – 141 004

CERTIFICATE  II

	This is to certify that the thesis entitled, "Screening of Agro-Physiological Traits for Thermotolerance in Wheat (Triticum aestivum L.)" submitted by Amandeep Kaur (L-2006-BS-130-M) to the Punjab Agricultural University, Ludhiana, in partial fulfillment of the requirements for the degree of M.Sc. in the subject of Botany (Minor subject: Biochemistry) has been approved by the Student's Advisory Committee along with Head of the Department after an oral examination on the same.

_______________________			________________________	
Head of the Department 				          Major Advisor		 
   (Dr. Kushal Singh)					(Dr. D.S. Gill)

________________________
Dean Post-Graduate Studies
    (Dr. (Mrs.) S.K. Mann)

ACKNOWLEDGEMENTS
 
	I have been able to bring this study in the present shake only because of hearty cooperation of a number of heads and hands.  There are some who have blessed, some assisted and some who have supplemented.  Thus each has contributed one's mind in some firm or the other. 
	It given me immense pleasure to express my sincere and whole hearted sense of gratitude to my Major Advisor, Dr. D.S. Gill, Sr. Plant Physiologist for his affectionate encouragement throughout the tenure of the present work.  My research would not have been successful without his inspiration and timely guidance.
	I am grateful to Dr. Kushal Singh, Sr. Plant Physiologist-cum-Head of Department of Botany and the members of my advisory committee, Dr. R.S. Sarlach, Associate Professor, Department of Plant Breeding and Genetics, Dr. J.S. Sital, Professor of Biochemistry, Department of Biochemistry, Dr. (Mrs.) Usha Parmar, Senior Botanist, Department of Botany for their constant help and invaluable guidance during the course of the investigation.  I also gratefully acknowledge the ever-willing cooperation of Dr. Karnail Singh, Sr. Statistician, Department of Plant Breeding and Genetics.
	It is rightly said that "Every effort is motivated by ambitious and all ambitions have an inspiration behind."  I owe this pride place to my parents Mr. A.S. Ghuman and Mrs. Lakhvir Kaur. 
	I offer my heartful appreciation to Jyoti, Rupinder, Amrit, Kanchan, Gurvir, Neha, Sharan, Harjot, Jasmeet, Jashan and my senior Tilak Raj for their ever willing cooperation, moral support and rendering valuable assistance whenever and wherever need arose.
	I also express my thanks to the supporting field staff for their help during my research work.
	I am extremely thankful to Mr. Deepak Kumar and Mr. Beer Bahadur (Ekta Computer Centre) for typing this manuscript neatly and meticulously.

(Amandeep Kaur)

Title of the Thesis	: 	Screening of Agro-Physiological Traits for Thermotolerance in Wheat (Triticum aestivum L.)

Name of the student	:	Amandeep Kaur 
and Admission No.	 	L-2006-BS-130-M

Major Subject	: 	Botany 

Minor Subject	: 	Biochemistry 

Name and Designation of 	: 	Dr. D.S. Gill 
Major Advisor                         		Senior Plant Physiologist 

Degree to be Awarded	: 	M.Sc.

Year of award of Degree	: 	2008

Total Pages in Thesis	: 	104	 

Name of University	:	Punjab Agricultural University,  Ludhiana, Punjab, India  
                                            
ABSTRACT
	Field and laboratory experiments were conducted at PAU, Ludhiana during rabi season 2006-07, to find out suitable agro-physiological traits for screening thermotolerance and relationship between yield and quality parameters in wheat.  The five wheat varieties namely PBW-502, PBW-343, WH-542, PBW-509 and Raj-3765 were sown at five dates at weekly interval starting from 7th November.  The Thermal unit (GDD) accumulated more during reproductive stages than those from vegetative stages in all the varieties.  This shows that rising temperature after anthesis is associated with grain filling and crop maturity.  The cv. PBW-343 had higher grain yield (51.44 q ha-1) due to its higher dry matter partitioning to spike at anthesis stage (0.31 g), crop growth rate after anthesis (6.75 mg cm-2 day-2), number of spike m-2 (523.60), 1000 grain weight (33.01 g) and chlorophyll content at milky stage (0.967 mg g-1 FW) followed by cv. WH-542.  With delay in sowing from 7th Nov. to 6th Dec., grain yield declined by 34.43, 37.89, 36.49, 28.89 and 33.16% in cvs. PBW-502, PBW-343, WH-542, PBW-509 and Raj-3765 respectively. The regression model showed significant positive correlation between grain yield and GDD accumulated during watery ripe (r=0.854), hard dough (r=0.849), anthesis (r=0.833) and physiological maturity (r=0.815) stages.  The correlation coefficient analysis also showed significant positive relationship between grain yield and physiological traits i.e. 1000-grain weight (r=0.9304), partitioning to spike at anthesis (r=0.8948), biological yield (r=0.8922), number of grains per spike (r=0.8351) and number of effective tillers m-2 (r=0.8323). Under late sown conditions, the amylose-amylopectin ratio increased and this character can be correlated with the superior end-use quality of grains.  These results indicated that number of effective tillers, leaf area index, pre-anthesis dry matter production, partitioning to spike at anthesis, grain growth duration, number of spikes m-2, number of grains per spike, 1000-grain weight, chlorophyll content at milky stage and thermal use efficiency which can be used as an index for screening thermotolerance in wheat cultivars.  

Key words : 	Wheat, Phenology Thermotolerance, Regression Equation, Correlation Coefficient, Growing - degree days, Amylose : Amylopectin, Grain yield 

 ___________________________   				    _____________________
 Signature of Major Advisor					    Signature of the Student

CONTENTS

Chapter		Topic	Page 	
I.	INTRODUCTION 	1-3	
II.	REVIEW OF LITERATURE 	4-23	
III.	MATERIALS AND METHODS 	24-38	
IV.	RESULTS AND DISCUSSION 	39-89	
V.	SUMMARY 	90-93	
	REFERENCES 	94-104	
	VITA 		

CHAPTER-I
INTRODUCTION 

		Wheat (Triticum aestivum L.) is the backbone of Indian Agriculture vis-a-vis economy.  Production and productivity of wheat both are maximum in the state of Punjab.  In 2006-2007 it was grown on 34.67 lac hectares with production of 145.96 lac tonnes and per hectare yield of 42.10 quintals (Anonymous 2008). However, wheat productivity is marked by various abiotic and biotic stresses. Amongst various abiotic and biotic factors temperature is the prime determinant of growth and productivity of wheat. In North-Western India, the remunerative rice (Oryza sativa L.)-wheat (Triticum aestivum L.) cropping system has forced wheat to be sown late in millions hectare area. 
		The late sown wheat crop is exposed to high temperature stress during the reproductive stages. The increased temperature hastens the phenological development of the crop, reduces total duration of crop growth, grain filling and finally lowering the grain yield and its quality (Sharma-Natu et al 2006). Globally about seven million hectare of wheat is affected by heat stress throughout its life cycle and 40% crop faces terminal heat stress (Sharma et al 2004). Genetic variability exists among different wheat genotypes for tolerance to high temperature during grain development phase. But for harvesting potential yield under a particular environment depends on the selection of suitable genotypes. Even in varietal improvement programme screening of suitable genotypes under a particular environment is most important.
		The accurate prediction of crop phenology is essential for screening purposes. Different threshold temperature and photoperiod could be used for predicting different growth stages. Even a particular growth stage may be best predicted by one model or other using the thermal and photothermal models (Pahwa 2002). The main criterion for selection or rejection is only grain yield.  However, if some agro-physiological traits are quantified with tolerance to late heat, it can be used to screen early germplasm material. Many physiological and biochemical traits have relationship with heat stress in wheat and are different at different phenological stages of the crop plant (Nagarajan and Rane 2002).
		Reduction in crop growth duration, adverse biochemical changes in the developing grain are some of the physiological traits that are affected by heat stress. The screening parameters which have large genotypic variability can be helpful in finding the differences more easily. High temperature during grain filling stage is an important yield determinant factor in wheat (Singh et al 2005).  There is a need to develop wheat varieties having tolerance to high temperature during grain development. Significant genetic variability in high temperature tolerance for grain growth and yield in wheat has been reported by Prakash et al (2004). Quality factors are important to a manufacturer attempting to produce a consistent product.  So attempt has been made to screen high temperature tolerant wheat varieties for different quality parameters. Moreover, screening based on single traits is not always be good for long term sustainability of genotypes (Turner 1996).  The present investigations are proposed to be undertaken with the following objectives :
-	Delineation of phenophases with thermal units i.e. Growing Degree-Days (GDD).
-	To find out the suitable physiological traits associated with screening thermotolerance in wheat cultivars.
-	Relationship between variation in yield and quality parameters under different environment. 

CHAPTER-II
REVIEW OF LITERATURE

		The relevant literature pertaining to “Screening of Agro-Physiological Traits for Thermotolerance in Wheat (Triticum aestiuum L.)" has been reviewed under the following headings:
2.1	Phenological development of the crop
2.2	Physiological traits 
2.3	Yield and yield contributing attributes
2.4	Biochemical analysis
2.1	PHENOLOGICAL DEVELOPMENT OF THE CROP
		Crop phenology can be used to specify the most appropriate rate and time of specific plant growth and development process. Phenology is the timing of the recurring of biological events and is an essential component of the crop-weather calender. The phenological development of the crop is affected by various abiotic stresses that are reviewed as under: 
2.1.1	Effect of Temperature
2.1.2	Effect of Light
2.1.1	Effect of Temperature

		Temperature is the prime weather variable which affects plant life. Temperature primarily controls the phyllochron, with light being a secondary factor in most of the crops (McMaster and Wilhelm 1995). The duration of particular stage of growth is directly related to temperature and the duration for particular species could be predicted using the sum of daily temperature (Nanda et al 1996). The day and night temperatures donot affect the plant independently and that the diurnal mean temperature is a better predictor of plant response to high temperature with day temperature having a secondary role (Peet and Willits 1998).
		Exposing wheat plants to high temperature at early stages can affect factors such as node extension and ear development, while temperature stress at anthesis and later can cause premature leaf senescence and can affect the fertility of the plant leading to reduced growth development (Wardlaw et al 1980). High temperature accelerate senescence, reduced the duration of viable leaf area and diminish photosynthetic activities (Harding et al 1990). High temperature during seed filling can accelerate senescence, diminish seed set and seed weight and reduce yield.  This is because under such conditions plants tend to divert resources to cope with the heat stress and thus limited photosynthates would be available for reproductive development (Wahid et al 2007).
		Rising temperature altered the growing season of agricultural crops by allowing the threshold temperature for the start of the season and crop maturity to reach earlier (Porter 2005). Dubey (1990) reported that when soil temperature was high, it accelerate the rate of germination and seedling emergence. Minimum temperature in temperate region may fall below –20C in early spring, photosynthesis and translocation of photoassimilates from the stem was restricted and killing the earheads. In wheat, pre-anthesis phenological phases which determine potential yield components are quite sensitive to high temperature (Abrol and Ingram 2005). Marcellos and Single (1972) found a pronounced reduction in the time from anthesis to maturity as temperature increased. The period between booting and anthesis (when carpels are growing fast) is most sensitive to high temperature (Calderini et al 2001).
		In many cereal crops, high temperature during the flowering phase can damage fertilization and seed production, resulting in reduced yield (Porter 2005). High temperature stress after anthesis severely reduces reproductive development in wheat (Al-Khatib and Paulsen et al 1984). There is significant positive correlation between grain yield and growing degree days (GDD) accumulated during ripening of grains (Pahwa 2002). High temperature stress has been reported as one of the most important cause of reduction in yield and dry matter production in many crops (Giaveno and Ferrero 2003).  High temperatures can cause considerable pre and post-harvest damages, including scorching of leaves and twigs, sunburns on leaves, branches and stems, leaf senescence and abscission, shoot and root growth inhibition and reduced yield (Vollenweider and Gunthardt-Goerg 2005).  Reproductive process are markedly affected by high temperatures in most plants, which ultimately affect fertilization and post-fertilization processes leading to reduced crop yield (Wahid et al 2007). 
		Warrington et al (1977) examined day length and temperature effects on the vegetative, ear development and post anthesis periods and found that grain dry weight was affected by environmental differences in all periods. Pal et al (1996) reported that all the phenophases except emergence exhibited higher accumulated growing degree days under earlier sowing followed by late sowing. The rate of development of wheat ear was greater and the final number of spikelets on the ear was less at a high temperature (300C) than at a low temperature (100C). 
2.1.2	Effect of Light
		Longer duration of stem elongation would increase spike dry weight in wheat due to higher accumulated intercepted radiation during that period (Akbar et al 2006). Higher radiation increases the amount of phytosynthates available for spike growth and lower temperatures prolong the period of spikelet growth and decrease competition for carbohydrates (Gonzalez et al 2005).  Singh et al (1988) reported increased chlorophyll under shade from 10% to 43%. Liu et al (1984) suggested that the increase in chlorophyll is due to the tendency of the rice crop to enrich the assimilatory system to produce more photosynthates and recommended that high total chlorophyll and low a-b ratio could be used as selection parameters to screen varieties for efficient photosynthesis at low light.
		McMaster et al (2003) reported that low light has a detrimental effect on the physiology and yield of the rice plant.  The effect is more predominant at the reproductive stage than at the vegetative stage.  The physiological parameters such as chlorophyll and soluble protein can be taken as selection indices for evaluating varieties grown under low light.  Sahu and Patro (1986) reported that the adverse effect of low light was less with plants exposed to shade during the vegetative stage than with those exposed during the reproductive stage. Low light also significantly reduced total dry matter per plant.
		Ewert (1996) observed significant positive correlation between thermal rate of spikelet and floret initiation and photoperiod in wheat and these relationships were consistent for all tiller numbers. Richard (2000) indicates a fall in the duration of grain filling as incident radiation rises. This could be due to an abbreviation of grain growth at higher levels of radiation and photosynthesis or to the higher temperatures which are often associated with higher radiations. 
2.2	PHYSIOLOGICAL TRAITS 
		The literature on the physiological traits associated with grain yield has been reviewed under the following subheadings :
2.2.1	Leaf Area
2.2.2	Dry Matter Production
2.2.3	Agrophysiological Traits
2.2.1	Leaf Area
		Determination of leaf area index can be useful for prediction of grain yield and grain quality in practice (Bavec et al 2007). According to Hundal and Kaur (1995) the reduction of Leaf Area Index (LAI) by 7.6 per cent in wheat and 5.9 per cent in rice was due to decrease in solar radiation by 100 per cent from normal. They also showed that with the increase in solar radiation by 10 per cent, leaf area index increases by 71 per cent in wheat. The slightly greater leaf area index of plants at high temperature could increase the far-red : red light ratio within the canopy, leading to leaves appearing faster (Barnes and Bugbee 1991).
		Singh et al (2005) reported that longer duration wheat genotypes had relatively higher values of photosynthetic rate compared to short duration genotypes. It seems that longer duration genotypes suffered a lot in respect of grain development under rising temperature compared to short duration varieties. Leaf area index showed a significant positive correlation with grain yield and biological yield (Singh et al 2006).  Reynolds et al  (1994) also reported a significant correlation between flag leaf photosynthesis measured after anthesis and grain yield in spring wheat genotypes grown in hot, irrigated conditions. This indicate that variation in photosynthetic rate of genotype at high temperature could be used to select for heat tolerance.
		Increasing leaf temperatures and photosynthetic photon flux density influence thermotolerance adjustments of photosystem-II indicating their potential to optimise photosynthesis under varying environmental conditions as long as the upper limits do not exceed (Marchand et al 2005).  Under high temperature conditions, earlier heading is advantageous in the retention of more green leaves at anthesis, leading to a smaller reduction in yield (Porter 2005).  Under high temperature, degradation of chlorophyll a and b was more pronounced in developed compared to developing leaves.  Such effects on chlorophyll or photosynthetic apparatus was suggested to be associated with the production of active oxygen species (Guo et al 2006). 
		Reynolds et al (2005) demonstrated high, positive correlation coefficients between grain weight and the components of photosynthetic area above the flag leaf node, both on per tiller and on per plant basis. On per tiller basis both grain weight and grain number gave correlation coefficients greater than +0.72 when correlated with either spike area, flag leaf sheath area, total photosynthetic area or total leaf area duration. 
2.2.2	Dry Matter Production
		Increase in leaf area index, dry matter production and yield components in early sown crop than the late sown crop because of maintenance of cool environment for longer period by early sown crop (Bahera 1994). Nagarajan and Rane (2002) found that tolerant genotypes produced significantly higher amount of biomass under stress environment (drought/temperature).
		The rise in temperature at grain development stage in very late sown crop have accelerated the rate of dry matter accumulation in spikes and reduced the length of reproductive period (Sardana et al 2003).  High temperatures caused significant declines in shoot dry mass, relative growth rate and net assimilation rate in maize, wheat and sugarcane (Wahid et al 2007).  Dry matter partitioning to leaves in wheat decreased throughout the growth season while to that of stem increased upto anthesis and thereafter it decreased upto physiological maturity (Akbar et al 2006). 
		Tewari and Singh (1995) also reported that the normal sown crop continued to produce dry matter at later stages and with delay in sowing, the rate of dry matter production decreases. The production efficiency of semi-dwarf wheat genotypes enhanced markedly under better crop nourishment mainly due to marked increase in their harvest index without significant improvement in biomass production (Reynolds et al  1999). Since harvest index is approaching a ceiling value, further increase in yield has to come through increase in crop biomass (Sharma-Natu and Ghildiyal 2005).
2.2.3	Agro-physiological Traits
		The agrophysiological traits at different growth stages of wheat reduced significantly with delay in sowing. They are used for screening wheat genotypes under different environments (Dogiwal et al  2004).  Reduction in leaf area, crop growth rate (CGR), grain growth rate (GGR), grain filling duration (GFD) and maturity duration in late sown wheat has been reported by Singh and Pal (2003). Late sowing decreased the grain growth duration and increased the grain growth rate (Sharma-Natu et al  2006). Nagarajan and Rane (2002) reported that biomass/m2, grain weight per spike, grain yield/m2 and grains/spike showed reduction under late sown conditions and can be used for selecting genotypes suitable for late sown conditions. 
		Singh et al  (2006) showed significant positive correlation of grain yield with leaf area index, biological yield, sink potential (grains/spike) and biomass partitioning (harvest index). So these traits can be used for screening purposes. Head stress lengthened the duration of grain filling with reduction in kernel growth leading to losses in kernel density and weight by upto 7% in spring wheat (Guilioni et al 2003). Grain yield was positively associated with fertile tillering, the number of spikes per square metre and thousand kernel weight (Moragues et al 2006). The larger tillering capacity and lower number of grains per spike may indicate a higher yield potential (Duggan et al  2000).
2.3	YIELD AND YIELD CONTRIBUTING ATTRIBUTES
		Literature regarding the yield and yield contributing traits are discussed below:
2.3.1	Grain yield
2.3.2	Yield contributing traits
2.3.1	Grain Yield
		Wheat is generally exposed to very low temperature up to booting stage, but later stages have to face warmer temperature that enable grain development under high temperature conditions (<250C) resulting in poor yield (Singh and Ahmad 1997). Rane et al (2000) found that the late sown wheat crop generally get exposed to high temperature regimes (35-400C) during grain filling period and suffer from grain yield reduction of 270 kg/ha/degree rise in temperature. The association between grain yield and morphological characters is better than plant water relation parameters and other physiological parameters like photosynthetic rate and transpiration rate. The simple reason of this variation seems to be their very small recording time on a particular day, whereas growth and yield parameters are the integration of whole season (Ludlow and Muchow 1990).
		Wang et al (2000) found that bigger the spike size, faster the floret initiation rate, which initiated more florets per spike and produced more fertile florets and grains, thus increasing yield. Singh and Pal (2003) reported that detrimental effect on grain yield was maximum through reduction in the number of grains per spike followed by 1000 grain weight and number of spikes per unit area under delayed sowing. The grain yield tended to decrease with higher temperature (> 280C) during the ripening period due to decrease in dry matter accumulation in the panicle (Oh-e et al 2006). In late sown wheat, the reproductive (anthesis to maturity) growth phases are exposed to high temperature stress during the month of March to April, which in turn reduce the growth, yield and quality of grains mainly by shortening of the reproductive phase and reduction in the number of effective tillers per unit area, number of grains per ear and 1000 grain weight (Nagarajan and Rane 2002).
		Dogiwal et al (2004) observed a correlation of grain yield with photosynthetic rate, grain growth rate, mobilization of pre-anthesis assimilates, canopy temperature depression (CTD), stay green score and attraction index. Sharma-Natu et al (2006) reported that pre-anthesis phenological events determining potential yield components would be affected by late sowing which are then carried over to the grain growth phase and influence grain growth and yield. 
		Donmez et al (2001) observed a positive correlation between above ground biomass and grain yield in winter wheat. Singh and Ahmad (1997) showed significant positive relationship of grain yield with effective ear number, biological yield and 1000-grain weight indicating their involvement in heat tolerance of wheat under late sown conditions. The pre-anthesis high temperature may also affect grain weight potential through its effect on growth of the ovaries which may in turn impose an upper limit for potential grain weight (Calderini et al 2001). Miralles et al (2000) reported that the duration of the late reproductive phase during which the spike and shoots compete for assimilates was associated with the number of fertile florets per spike suggesting that extending the stem elongation period in cereals could be a way to reduce assimilate competition and to increase the grain yield.
		In many crop plants, early maturation is closely correlated with smaller yield losses under high temperatures, which may be attributed to the engagement of an escape mechanism (Adams et al 2001). Sink capacity is a major limiting factor for crop productivity, a physiological stress-related decrease in sink activity directly affects grain yield in wheat (Reynolds et al 2005).  Increased mobilization efficiency of reserves from leaves, stem or other plant parts has been suggested as a potential strategy to improve grain filling and yield in wheat under heat stress (Wahid et al 2007).
		Tahir et al (2006) reported that the mean reduction in yield for the 30 rise to 280 was 8.4% and it was 16.4% for the 60 to 310C. Kumar et al (1994) reported that the highest yield was obtained from early sown varieties and poorer grains were obtained from late sown wheat varieties. 
2.3.2	Yield Contributing Traits 
 		Ugarte et al (2007) reported that yield of grain crops integrates two main components i.e. grain number per square metre and average grain weight. The most probable effect of high temperature on grain yield was due to: (1) Decrease in grain weight when high temperature applied only to spikes between heading and anthesis (Calderini et al 2001). (2) Decrease in the growth rate of florets at high temperature. (3) Decrease in final grain weight which was associated with carpel weight at anthesis.
		High temperature effect on one component of yield influence the other component because of yield components compensation (Slafer et al 1996). Samre et al (1989) observed decrease in 1000 grain weight resulting in lower grain yield under delayed sowing. Kumar et al (2001) reported that number of spikes/meter row length, test weight and days taken to maturity emerged as important attributes influencing seed yield in wheat. Rane and Nagarajan (2001) reported that the correlation between the Ear: Stem ratio was not as efficient as harvest index (HI) in differentiating susceptible and tolerant wheat genotypes. The genotypes with medium to bold grain and early maturity escape heat stress and perform well under late sown conditions (Rane et al 2000).
		Singh and Pal (2003) showed that significant reduction in grain yield of wheat cultivars by delayed sowing could mainly have resulted from marked reduction in sowing to anthesis and anthesis to maturity durations which in turn reduced the build up of growth and yield components such as tillering, photosynthetic surface per shoot, biological yield, number of grains per spike and 1000-grain weight markedly without marked reduction in harvest index and grain growth rate. 	
		Genotypic differences in high temperature tolerance were more pronounced in grain yield than in biomass yield (Tahir and Nakata 2005).  Wheat is affected by high temperature stress especially during grain filling period which exerts a large impact on grain quality (Wardlaw et al 2002).  The grain number is closely associated with number of fertile florets at anthesis increasing spikelet rachilla rachis (florets stalk) fertility to improve wheat yield potential (Araus et al 2002).  The variety which gives more number of effective tillers even under late to very late sown conditions will eventually give higher yield (Sardana et al 2003). 
2.4	BIOCHEMICAL ANALYSIS 
		The literature on various aspects of biochemical parameters are discussed under the following main points:
2.4.1	Chlorophyll content
2.4.2	Quality parameters
2.4.1	Chlorophyll Content
		Harding et al (1990) estimated that photosynthesis in the ear might account for 70 percent of the dry weight of the grain and all starch, the remaining 30 percent of the grain weight consisting of non-starch material arising from assimilation in the flag leaf and sheath which remain green as long as the ear. Stress reduces yield by decreasing source activity which is especially critical because most grain mass is from current photosynthesis after anthesis (Evans et al 1975).
		The main effect of high temperature on the chloroplasts are on the proteins of the thyakoid membrane. The thylakoid membranes become disoriented relative to the long axis of the chloroplasts and the membrane unstacks, causing loss of chloroplasts (Xu et al 1995). High temperature reduces the size of sink (due to fall in grain number per ear) as a result there is significant feed back inhibition of photosynthesis of the source (spikelet husk) supplying the developing ear. (MullarKey and Jones 2000). Herzog (1982) found that sink activity is measured by grain growth rate while activity of source was monitored by the chlorophyll content of flag leaf. Evans (1992) reported that the significant reduction in mobilization of pre-anthesis assimilates in late-sown wheat which might be due to poor growth of the source i.e. leaves and stem ultimately resulting in lower translocation to developing sink at the time of maturity. The ability of a plant to retain chlorophyll under stress is generally known as stay-green trait and the identification of plants displaying this trait could aid in producing new wheat cultivars with improved thermotolerance (Thomas and Howarth 2000).
		Shubhra et al (2006) found that late sowing decreased photo- synthetic pigments compared to timely sowing conditions. On average, chlorophyll a decreased by 29%, chlorophyll b by 38% and carotenoids by 12% due to late sowing. The highest detrimental effect of delayed sowing was noted in chlorophyll b followed by chlorophyll a and carotenoids. A highly significant positive correlation was observed between stomatal conductance and grain yield.
		Richard (2000) found that the highest yielding genotype have a lower assimilation capacity per unit area than the lowest yielding lines or line with highest stomatal conductance have the highest yield. Ristic et al  (2007) reported that the wheat varieties that suffered more damager to thylakoid membranes (displayed lower tolerance to heat stress) under heat stress lost more chlorophyll than cultivars that suffered less damage (displayed higher tolerance to heat stress). So, loss of chlorophyll under heat stress could be used as a reliable and appropriate method for screening thermotolerance in wheat. The differences in tolerance of moderately high temperature in wheat is related to the stability of Rubisco function and to ribulose bisphosphate regeneration activity rather than to the effects on activity or stomatal control (Stasik et al 2007). Fischer et al (1998) found that stomatal conductance, canopy temperature depression and maximum photosynthetic rate were all associated with yield progress. 
2.4.2	Quality Parameters
2.4.2.1	Total starch i.e. amylose and amylopectin
2.4.2.2	Total protein and its major fraction i.e. Gluten
		Quality refers to the desirability of the product and may include various physical , chemical, protein content, its quality and alpha amylose activity. High temperature influences both grain yield and end-use quality of wheat (Tahir et al 2006). Ristic et al  (2007) reported that a major effect of high temperature on wheat is acceleration of senescence, which is manifested by an increase in the activity of proteolytic enzymes leading to protein degradation and chlorophyll loss. 
		Starch accumulation and starch granule size were reduced at high temperature in barley, but amylose contents were little affected and no change in amylopectin fine structures was detected (MacLeod and Duffs 1988). Shi et al (1994) reported that with increasing temperature during grain filling, amylose content was slightly increased and starch gelatinization temperatures increased. Environmental temperature affects grain yield, protein content, size and number of starch granules (Bhullar and Jenner 1985). Maize grown at higher temperature during endosperm cell division had reduced kernel mass due to reduced number of endosperm cells, starch granules or both (Jones et al 1985). Zhao-Hui et al (2006) reported that the contents of total starch and amylopectin were markedly reduced but amylose content was slightly affected and the ratio of amylopection to amylose was reduced significantly in higher temperature treatments. 
		Yong Cheng (1994) reported that growth of wheat at higher temperature resulted in shrivelled kernels, reduced kernel weight, reduced starch accumulation and reduced starch granule size. Deformed starch granules were observed in wheat grown at 400C. Starch-lipid levels increased with increasing grain filling temperature, amylose levels were slightly increased. It has been shown by Chaudhary et al (1994) that the soluble form of starch synthase exhibits enhanced activity in developing seeds of tolerant types under post-anthesis heat stress and this was not accompanied by an expected increase in the dry weight of the grain although the reduction in grain weight was insignificant under heat stress as compared to control.
		The increase in amylopectin percent in starch in the tolerant types appears to be atleast on two counts, first to partition and accommodate more carbon in the grain under heat stress which is known to reduce the grain development time considerably and may involve both the soluble starch synthase and the branching enzyme. Second, the starch with higher amylopectin content is capable of holding more water effectively (Pande et al 1998). Park et al (2006) stated that both quantity and quality of proteins affected bread making properties such as tolerance, water absorption, leaf volume and crumb characteristics. Positive correlations between the temperature during the early stages of grain filling and wheat protein content have been reported by Blumenthal et al (1995). The results of Rao et al (1993) indicated that the protein composition as well as protein content was affected by temperature because the ratio of alkali-soluble to salt-soluble proteins increase with increasing temperature. Increase in grain protein content resulting from high temperatures during grain development were associated with greater dough resistance to extension, but lower extensibility than that of dough from grains of similar protein content produced at lower temperature (Uhlen et al 1998). Blumenthal et al (1995) described a loss in dough strength in Australian wheats that was proportional to the number of hours at high temperatures (>350C) during grain filling and attributed this effect to a differential synthesis of gliadins, as opposed to glutenins during period of heat stress. High temperature stress decreased the glutenin-to-gliadin ratio and the proportion of very large glutenin polymers.
		High temperatures are known to influence the rate of conversion of sucrose to starch by reducing the activity of soluble starch synthase leading to shorter duration of grain filling (Sardana et al 2003).  High temperatures during grain filling can modify flour and bread quality and other physico-chemical properties of grain crops such as wheat including changes in protein content of the flour (Wardlaw et al 2002).  Reductions occurred in starch, protein and oil contents of the maize kernel and grain quality in other cereals under heat stress (Maestri et al 2002).
		Results of Tahir et al (2006) indicate that high temperature increased both soluble and insoluble protein contents and hence the gluten strength but decreased flour mixing time and tolerance and hence the dough elasticity. Variation observed among genotypes suggests that grain end-use quality could be improved under high temperature conditions utilizing the available variability. Habbal et al (2000) reported that delay in sowing date increased the crude protein, wet and dry gluten contents, bran and middling percentage but reduced flour percentage and the capacity of gluten to absorb water. The increment in grain protein content under high temperature was associated with the increase in the free amino acid content of vegetative organs and with enhanced utilization of amino acids in grains (Zhao-Hui et al 2005).
		Graybosch et al (1995) found a negative correlation between protein content and duration of the grain filling period. Uhlen et al (1998) reported that protein content and dough mixing properties were affected by the temperature during grain filling. Selection of cultivars with strong mixing properties become even more important to ensure good and stable wheat quality in areas where the temperature during grain filling is low as compared to areas with higher temperatures. 

CHAPTER III
MATERIALS AND METHODS

		A brief account of material used and methodology adopted during conduct of the present investigation is present in this chapter. 
3.1	LOCATION AND CLIMATE 
		The present investigation entitled, “Screening of Agro-physiological traits for thermotolerance in wheat (Triticum aestivum L.)” was conducted at the experimental area of the Department of Botany, Punjab Agricultural University, Ludhiana during the rabi season 2006-2007. Ludhiana representing the Indo-Gangetic alluvial plains is situated at 30°-54'N latitude, 75°-48'E longitude and at a mean height of 247 meters above sea level. Ludhiana is placed in South-Central plain region of Punjab having subtropical and semi-arid climate. The mean temperature shows fluctuations during summer and winter seasons. The meteorological data collected from meteorological observatory, Punjab Agricultural University, Ludhiana for the season 2006-07 are presented in Fig. 3.1 and 3.2.
3.2	SOIL ANALYSIS
		A composite soil sample of experimental area from 0-15 cm depth was taken to determine the physico-chemical properties of the soil before sowing. The physico-chemical properties of the soil are given in Table 3.1.

25

26

Table 3.1   Physico-chemical analysis of the soil
Soil Property 	Value/content	Method employed	
Texture 	Loamy sand	International pipette method (Piper 1966).	
pH	8.20	Beckman’s glass electrode pH meter in 1:2 soil suspension (Jackson 1967).	
Electrical Conductivity (mm hos cm-1)	0.04	In 1:2 soil: water suspension with Elico conductivity meter (Jackson 1967).	
Organic carbon (%)	0.12	Walkley and Black’s Rapid Titration Method (Subbiah and Asija 1956).	
Available N  (Kg ha-1)	130	Modified alkaline potassium permanganate method (Subbiah and Asija 1956).	
Available P  (Kg ha-1)	33.2	0.5N NaHCO3 extractable P i.e. Oslen’s method (Oslen et al 1954).	
Available K (Kg ha-1)	187	1N ammonium acetate extractable K (Jackson 1967).	

3.3	EXPERIMENTAL DETAILS AND LAYOUT 
	Treatments 
i)	Cultivars (5)		ii)	Dates of sowing (5)  
	PBW-502 (V1)			7th November 2006 (D1)
	PBW-343 (V2)			15th November 2006 (D2)
	WH-542 (V3)		         22nd November 2006 (D3)
	PBW-509 (V4)			29th November 2006  (D4)
	Raj-3765 (V5)			6th December 2006 (D5)

iii)	Total number of treatments 	: 	5 x 5 = 25
iv)	Layout Design			:	Split plot design
v)	Number of replications 		:	3
vi)	Total number of plots		:	75	
vii)	Plot size				:	12' x 10' 
viii)	Row to row distance		:	22.4 cm
3.4	CULTURAL OPERATIONS 
3.4.1	Preparation of Field 
		The field was ploughed twice with a cultivator and then was planked. The recommended package of practices for wheat crop was followed (Anonymous 2008). 
3.4.2	Sowing and Harvesting 	
		The crop was sown on 7th November, 15th November, 22nd November, 29th November and 6th December 2006 (five dates of sowing). The sowing was done with a manual drill at a spacing of 22.4 cm from row to row. The harvesting was done manually with sickles and threshed.
3.5	OBSERVATIONS RECORDED
3.5.1	Different Phenological Stages of the Crop
		Four plants from each replication were randomly selected and tagged for different phenological stages i.e. seedling emergence to physiological maturity. The diagrammatic view of different growth stages in wheat cultivar are given in Fig. 3.3.

29

Fig. 3.3  Different phenological stages in wheat 

a)	Seedling Emergence: Seedling emergence was noticed when the coleoptile had emerged from the soil.
b)	Crown Root Initiation (CRI): This stage was recorded generally after 15 days of sowing. Crown was visible at 2-3 cm below soil surface and usually separated from the seed by a sub-crown internode.
c)	Leaf Development: Leaf development was noticed starting from the appearance of first leaf upto flag leaf on the main shoot.
d)	Tillering: Tillering was recorded from the appearance of first tiller to last tiller.
e)	Stem Elongation: This stage was noticed from the appearance of first node to last node on the main shoot.
f)	Booting: Inflorescence started swelling within the flag leaf sheath during the booting stage. The booting stage ends when the first awn emerged from the flag leaf sheath and the head started to force the sheath open. 
g)	Inflorescence (emergence and heading): This stage was recorded starting from the emergence of the first spikelet in the inflorescence upto complete ear head emergence.
h)	Anthesis: Anthesis is usually noted by extrusion of the anthers from each floret.
i)	Watery Ripe: Watery ripe stage was noticed when the grains yielded a watery fluid on pressing between the thumb and the forefingers.
j)	Milky Ripe: When the grains yielded a milky fluid on pressing between the thumb and the forefingers, it represented the milky ripe stage.
k)	Soft Dough: In soft dough stage, waxy ripe glutin like sticky feel obtained upon pressing the developing seed between the fingers. 
l)	Hard Dough: When the grains turned hard and difficult to crack, it represented the hard dough stage.
m)	Physiological Maturity: This stage was attained when the inflorescence lost all the green colour, the peduncle turned yellow, but the uppermost node still remained green and grains become hard.
3.5.2	Growth Parameters
a)	Emergence Count m-2: Emergence count from one metre square  area was recorded after germination.
b)	Number of Tillers m-2: The number of tillers from one metre square area were counted after the completion of tillering stage. 
c)	Leaf Area Index (LAI): Leaf area index of uniform plants from each replication at 90 days after sowing of five wheat cultivars under five dates of sowing was calculated by the following formula:
Leaf area (L x B x 0.81)
			LAI	=	
					  Ground surface area
	L – Length		B – Breadth 	0.81 – constant for wheat
d)	Crop Growth Rate (mg cm-2 day-1): Dry weight of uniform plants from each replication at 90 and 120 days after sowing was taken and crop growth rate (CGR) was calculated by using the following formula:
   W2 – W1
	CGR	=	
			SA (T2 – T1)
	W2-W1	= Weight of plant at two different time intervals (W)
T2-T1  	= Time intervals  (T)
SA		= Soil surface area covered by plant		
e)	Pre-anthesis Dry Matter Production (%) : It was determined by using the method of Singh and Pal (2003).
    Total dry wt. at anthesis
	Pre-anthesis dry matter Production (%) =				  x100
							    Total dry wt. at maturity
f)	Total number of Leaves on Main Shoot: Total number of leaves on main shoot of four selected plants in each plot were counted at the booting stage.
g)	Spike Weight at Anthesis Stage: Five uniform spikes from each replication were taken and their dry weight was recorded (Siddique and Whan 1994).
h)	Partitioning to Spike at Anthesis Stage: It was calculated by dividing the dry weight of spikes to the total plant dry weight at anthesis stage.
i)	Grain Filling Rate (mg/grain/day): A sample of five uniform spikes from each replication after every 10 days from anthesis till maturity, was collected from each plot. Samples were dried at 550C for 48 hrs and then threshed and dry grain weight (mg/grain/day) was calculated (Randhawa et al 1992).
j)	Grain Growth Duration: The duration of grain growth period (days) was calculated from anthesis to physiological maturity stage.
k)	Plant Height (cm): The plant height of four uniform plants in each replication was measured from ground level to the top of ear including awns at maturity. 
3.5.3	Yield and yield contributing attributes 
a)	Effective Tillers/ Number of Spikes m-2: The ear bearing tillers and number of spikes were counted from one metre square area at the time of harvest.
b)	Number of Grains/Spike: Five spikes from each replication were used for counting the number of grains per spike.
c)	Grain-Spike Weight Ratio: The grain-spike weight ratio was determined by dividing the grain weight with spike weight at maturity.
d)	1000 Grain Weight (gm): One thousand randomly grains from bulk produce of each plot were taken and their weight (gm) was recorded.
e)	Biological Yield (q ha-1): Total biological yield was recorded after harvesting the crop.
f)	Grain Yield (q ha-1): Grain yield was recorded after harvesting and threshing the crop.
g)	Harvest Index (HI): Harvest index was calculated by using the following formula:
   Grain yield
		Harvest index (HI)	=				x 100
						Biological yield	
3.6	GROWING DEGREE-DAYS (GDD) FOR DESCRIBING PHENOLOGICAL DEVELOPMENT

		Phenological development of the wheat cultivars (PBW-502, PBW-343, WH-542, PBW-509 and Raj-3765) were computed by using growing degree-days units (GDD), (Baker et al  1990).
Growing Degree Days (GDD)	=            
n  =   Number of days in between two successive phenological stages.
Tmax	= Maximum temperature (0C) of the day.
Tmin	= Minimum temperature (0C) of the day.
Tb	= Base temperature below which leaf appearance rate reached zero. 	   (Tb = 50C)
3.7	BIOCHEMICAL ANALYSIS
3.7.1	Extraction and Estimation of Chlorophyll
		The method of Anderson and Boardman (1964) was followed to estimate chlorophyll. 100 mg of central spikelet husk were crushed  in 5 ml of 80% acetone in a pestle and mortar. The extract was centrifuged at 3 x 1000 rpm for 10 min. The supernatant was retained and the residue again crushed in 3 ml of 80% acetone. The two supernatant were pooled and the final volume was adjusted to 10 ml with 80% acetone. Absorbance was recorded at 645 and 663 nm and chlorophyll was calculated by using following formulae:
							       	       V
Chlorophyll a   = [12.7 (A 663) – 2.69 (A 645)] x  
							           1000 x W 

							                V
Chlorophyll b = [22.9 (A 645) – 4.86 (A 663)] x  
							          1000 x  W 

							                   V
Total Chlorophyll = [20.2 (A 645) + 8.02 (A 663)] x 
							               1000 x W 

where:
V = Total volume of the extract (ml)
W = Fresh weight of the sample (g)	A 663 = Absorbance at 663 nm
A 645 = Absorbance at 645 nm	
	The chlorophyll content is expressed as mg g-1 FW.
3.7.2	Quality Analysis of Grains
a)	Total Protein
Total protein was determined by the method of Lowry et al (1951)
Extraction: 100 mg of dried material of wheat flour was homogenized in 5 ml of 0.1 N NaOH followed by centrifugation and the supernatant was collected. The residue was again homogenized in 3 ml of 0.1 NaOH. The two supernatants were pooled and the final volume was adjusted to 10 ml with 0.1N NaOH. The supernatant was treated with 15% TCA and kept at 40C for 24h. Proteins were precipitated and centrifuged at 5 x 1000 rpm for 20 min to separate the precipitated proteins. Precipitates were dissolved in 0.1 NaOH.
Reagents: 
	Sol A – 2% Na2CO3 in 0.1N NaOH.
	Sol B – 0.5% CuSO4. 5H2O in 1% sodium potassium tartarate. 
	Sol C – Mixed Sol. A (50 ml) and Sol.B (1 ml) at the time of use.
	Sol D – Folin-ciocalteau reagent diluted to 50% with distilled water 		  at the time of use	.	
Estimation: 5 ml of Sol. C was added to protein extract. After shaking, it was left at room temperature for 10 minutes. Sol. D was added to this solution. This was kept at room temperature for 30 min and absorbance of blue colour obtained was recorded at 570 nm (SL-159 UV-VIS spectrophotometer). 
Gluten: Gluten was determined by the method from (Anonymous 1976).
Procedure: Weigh 25g flour into mortar, added sufficient tap water to form firm dough ball, taking care that no material adhere to utensils. Dough placed in water at room temperature for 1 hr. Knead dough gently in stream of tap water over bolting cloth, until starch and all soluble matter are removed. This step requires approximately 12 minutes. To determine whether or not gluten is approximate starch free, let 1 or 2 drops of wash water, obtained by squeezing, fall into beaker contained perfectly clear water. If starch is present, cloudiness appears. Gluten thus obtained by washing stand in water for 1 hr. Press as dry as possible between the hands, roll into a ball place in weighed flat-bottomed dish and weigh as moist gluten. Transfer to oven, dry to constant weight at 1000C (24 hrs) cool and weigh as dry gluten.
					Dry weight of gluten
	Gluten % (dry basis) = 				       x 100
					         Sample wt.	
					Wet weight of gluten
	Gluten % (wet basis) =				      x 100
					         Sample wt.	
b)	Total Starch
		Total starch was extracted by the method of Clegg (1956).
Extraction: 200 mg of dried residue, that left after extraction of sugar was used to determine starch. In this residue 5ml distilled water and 6.5 ml chilled 52% perchloric acid was added and stirred continuously for 10 minutes, and then added 10 ml distilled water and centrifuged for 20 minutes. Supernatant was poured in volumetric flask. The extraction was repeated twice with pellet for 30 minutes. Supernatant was diluted to 100 ml with water and this solution was then filtered through Whatman filter paper, discarded the first 5 ml of the filtrate.
Estimation: Estimation of sugar by Dubois et al (1956). 1 ml extract was taken and added 1 ml of 5% phenol and 5 ml concentrated H2SO4. Absorbance of the colour thus obtained was read at 490 nm (SL-159 UV-VIS Spectrophotometer).
Amylose 
		Amylose was determined by the method of Sadasivan and Manickam (1972).
Procedure: Taken 100 mg of the wheat flour and added 1 ml of distilled ethanol. Then added 10 ml of 1N NaOH and left overnight. After this, the volume of the extract was made to 100 ml with distilled water. Then take 2.5 ml of the extract in a 50 ml volumetric flask and added 20 ml distilled water and three drops of phenolphthalein. Then 0.1 N HCI was added drop by drop till the pink colour just disappeared. After disappearance of pink colour 1 ml of iodine was added and made up the volume to 50 ml and absorbance of the colour developed was read immediately at 590 nm (SL-159 UV-VIS Spectrophotometer).
3.8	STATISTICAL ANALYSIS
		The data was subjected to standard statistical analysis for calculating critical difference, regression equations (Singh et al 2001) and path coefficient analysis (Dewey and Lu 1959).

CHAPTER-IV
RESULTS AND DISCUSSION

		Yielding potential of wheat is likely to be marked by various biotic and abiotic stresses, operating in the field. Amongst the abiotic stresses, temperature have emerged as a yield determinant factor in wheat.   Crop growth models have become important tools for understanding and improving crop management.  In the present study, results of the field and laboratory experiment are presented and discussed under the following headings :
4.1	Phenological development of the crop
4.2	Physiological traits 
4.3	Yield and yield contributing attributes
4.4	Biochemical analysis
4.1	PHENOLOGICAL DEVELOPMENT OF THE CROP
		Phenological development of the wheat varieties (PBW-502, PBW-343, WH-542, PBW-509 and Raj-3765) under different dates of sowing are presented in Fig 4.1 (A, B and C) and Tables 4.1 to 4.5 i.e. seedling emergence, crown root initiation, leaf development, tillering, stem elongation, booting, inflorescence, anthesis, watery ripe, milky ripe, soft dough, hard dough and physiological maturity. 

Table 4.1   Complete phenological development of wheat variety PBW-502 under different dates of sowing

Sr. No.	Phenophases	7th Nov.		15th Nov.		22nd Nov.		29th Nov.		6th Dec.	
		DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	
1.	Seedling emergence	6	106	6	88.5	7	74.8	7	72.3	8	63.3	
2.	Crown root initiation	23	324.5	24	273.1	26	246.1	26	235.7	27	220.5	
3.	Leaf development	85	805.8	85	760.7	82	701.2	79	657.2	77	625.9	
4.	Tillering	73	693.6	74	629.8	73	582.9	76	635.8	78	636.1	
5.	Stem elongation	79	735.5	78	677.5	76	632.3	76	635.8	75	608.4	
6.	Booting	107	1023.1	106	1012.9	106	939.3	98	853.4	92	792.2	
7.	Inflorescence (emergence and heading)	112	1078.3	110	1007.1	110	991.2	106	949.9	101	899.0	
8.	Anthesis	115	1112.3	114	1053.1	114	1034.7	107	959.9	103	927.5	
9.	Watery ripe	121	1179.2	121	1136.3	119	1110.7	109	984.2	106	981.8	
10.	Milky ripe	128	1264.6	127	1230.5	125	1204.3	118	1129.5	113	1092.2	
11.	Soft dough	144	1520.5	138	1429.6	136	1419.2	127	1304.9	123	1293.5	
12.	Hard dough	156	1765.7	151	1700.0	145	1624.2	140	1603.5	136	1597.4	
13.	Physiological maturity	160	1864.1	155	1799.7	149	1720.3	144	1693.7	139	1671.2	

Table 4.2   Complete phenological development of wheat variety PBW-343 under different dates of sowing
Sr. No.	Phenophases	7th Nov.		15th Nov.		22nd Nov.		29th Nov.		6th Dec.	
		DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	
1.	Seedling emergence	6	106	6	88.5	7	74.8	7	72.3	8	63.3	
2.	Crown root initiation	22	314.7	24	273.1	26	246.1	26	235.7	27	220.5	
3.	Leaf development	88	837.8	87	783.4	87	750.6	85	708.4	84	702.6	
4.	Tillering	76	715.7	76	655.6	76	632.3	78	649.4	78	636.1	
5.	Stem elongation	84	793.9	82	722.3	80	681.8	80	665.8	79	646.6	
6.	Booting	110	1054.5	109	995.3	106	939.3	100	876.7	95	832.0	
7.	Inflorescence (emergence and heading)	118	1145.4	115	1066.7	112	1014.5	106	949.9	103	927.5	
8.	Anthesis	119	1157.9	118	1104.0	114	1034.7	109	984.2	106	981.8	
9.	Watery ripe	125	1231.1	122	1147.7	118	1091.4	112	1035.9	106	981.8	
10.	Milky ripe	129	1274.6	128	1244.6	127	1239.3	121	1184.4	114	1112.1	
11.	Soft dough	140	1444.2	137	1405.4	135	1399.4	130	1365.8	126	1356.7	
12.	Hard dough	158	1813.4	153	1751.6	149	1720.3	145	1717.7	140	1696.5	
13.	Physiological maturity	162	1918.2	156	1821.9	153	1818.3	149	1817.5	142	1745.2	

Table 4.3   Complete phenological development of wheat variety WH-542 under different dates of sowing
Sr. No.	Phenophases	7th Nov.		15th Nov.		22nd Nov.		29th Nov.		6th Dec.	
		DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	
1.	Seedling emergence	6	106	6	88.5	7	74.8	7	72.3	8	63.3	
2.	Crown root initiation	22	314.7	24	273.1	26	246.1	26	235.7	27	220.5	
3.	Leaf development	86	815.8	87	783.4	87	740.6	86	718.9	84	702.6	
4.	Tillering	72	686.8	74	629.8	73	597.9	73	607.0	74	601.4	
5.	Stem elongation	84	793.9	81	709.4	81	693.1	79	657.2	79	646.6	
6.	Booting	109	1043.7	108	983.8	102	893.7	99	864.5	92	792.2	
7.	Inflorescence (emergence and heading)	115	1112.3	114	1053.1	112	1014.5	108	971.3	102	911.9	
8.	Anthesis	116	1122.1	116	1070.7	113	1024.7	108	971.3	103	927.5	
9.	Watery ripe	120	1168.1	120	1126.3	116	1059.0	109	984.2	105	963.6	
10.	Milky ripe	129	1274.6	127	1230.5	126	1221.1	122	1205.8	118	1199.1	
11.	Soft dough	140	1444.2	138	1429.6	136	1419.2	132	1407.1	126	1356.7	
12.	Hard dough	156	1765.7	153	1751.6	150	1744.5	145	1717.7	139	1671.2	
13.	Physiological maturity	160	1864.1	156	1821.9	153	1818.3	149	1817.5	142	1745.2	

Table 4.4   Complete phenological development of wheat variety PBW-509 under different dates of sowing

Sr. No.	Phenophases	7th Nov.		15th Nov.		22nd Nov.		29th Nov.		6th Dec.	
		DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	
1.	Seedling emergence	6	106	6	88.5	7	74.8	7	72.3	8	63.3	
2.	Crown root initiation	22	314.7	22	259.1	24	227.3	24	219.1	25	212.0	
3.	Leaf development	65	650.1	70	590.0	71	575.9	70	571.3	70	569.8	
4.	Tillering	67	659.5	68	577.4	68	540.3	65	511.6	64	512.0	
5.	Stem elongation	69	668.6	66	564.2	65	506.0	63	491.1	62	485.2	
6.	Booting	86	815.8	87	783.4	90	764.3	89	751.5	85	713.9	
7.	Inflorescence (emergence and heading)	102	980.5	99	884.8	98	849.7	97	843.2	94	818.0	
8.	Anthesis	104	995.4	103	927.9	103	906.2	102	904.3	100	887.6	
9.	Watery ripe	108	1033.6	108	983.8	106	939.3	103	916.4	102	911.9	
10.	Milky ripe	126	1242.3	126	1212.3	125	1204.3	118	1129.5	114	1112.1	
11.	Soft dough	141	1461.0	138	1429.6	135	1399.4	128	1324.6	123	1293.5	
12.	Hard dough	156	1765.7	151	1700.0	145	1624.2	139	1575.2	135	1573.2	
13.	Physiological maturity	160	1864.1	155	1799.7	148	1698.1	142	1645.5	138	1645.4	

Table 4.5   Complete phenological development of wheat variety Raj-3765 under different dates of sowing

Sr. No.	Phenophases	7th Nov.		15th Nov.		22nd Nov.		29th Nov.		6th Dec.	
		DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	
1.	Seedling emergence	6	106	6	88.5	7	74.8	7	72.3	8	63.3	
2.	Crown root initiation	23	324.5	24	273.1	25	237.0	25	227.9	25	212.0	
3.	Leaf development	65	650.1	70	590.0	71	575.9	69	557.5	65	523.4	
4.	Tillering	68	664.1	69	582.7	72	586.4	73	607.0	68	554.1	
5.	Stem elongation	64	762.7	62	535.4	60	470.0	60	453.4	58	439.3	
6.	Booting	88	837.8	90	812.2	88	748.5	88	739.8	85	713.9	
7.	Inflorescence (emergence and heading)	102	980.5	97	865.9	95	814.6	93	797.6	90	770.9	
8.	Anthesis	105	1004.2	103	927.9	102	893.7	98	853.4	94	818.0	
9.	Watery ripe	109	1043.7	108	983.8	107	951.5	103	916.4	99	877.6	
10.	Milky ripe	127	1254.4	126	1212.3	117	1074.6	114	1068.2	111	1057.2	
11.	Soft dough	141	1461.0	138	1429.6	136	1419.2	132	1407.1	126	1356.7	
12.	Hard dough	153	1701.3	149	1650.6	146	1650.0	140	1603.5	136	1597.4	
13.	Physiological maturity	159	1838.3	154	1779.9	149	1720.3	143	1669.7	139	1645.4	

4.1.1.	Seedling emergence

Dates of                sowing	PBW-502, PBW-343, WH-542, PBW-509 and Raj-3765	
	Days after sowing 	GDD	
7th Nov.	6	106	
15th Nov.	6	88.5	
22nd Nov.	7	74.8	
29th Nov.	7	72.3	
6th Dec.	8	63.3	

		Seedling emergence was observed after 6 days under7th Nov.  and 15th Nov., 7 days under 22nd Nov.  and  29th Nov.  and 8 days under 6th Dec. sowing in all the varieties of wheat. This showed that seedling emergence took more number of days with delay in sowing. This may be due to decreased soil temperature resulting in reduced metabolic activity of the seed. The Growing Degree Days (GDD) required for the seedling emergence were maximum (106) under 7th November  and minimum (63.3) under 6th December sowing. This indicates that GDD decreased with delay in sowing (Sekhon 1987).
4.1.2	Crown Root Initiation 
		The number of days taken up by the crop for crown root initiation increased with delay in sowing from 7th Nov. to 6th Dec. The accumulated Growing Degree Days (GDD) were maximum (324.5) in PBW-502 and Raj-3765 varieties under normal (7th Nov.) sowing and minimum (212.0) in PBW-509 and Raj-3765 varieties under late (6th Dec.) sowing.  GDD units decreased with delay sowing in all the varieties.
		The number of days and accumulated GDD units for different wheat varieties from sowing to CRI are given below:
Dates of sowing	PBW-502		PBW-343		WH-542		PBW-509		Raj-3765	
	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	
7th Nov.	23	324.5	22	314.7	22	314.7	22	314.7	23	324.5	
15th Nov.	24	273.1	24	273.1	24	273.1	22	259.1	24	273.1	
22nd Nov.	26	246.1	26	246.1	26	246.1	24	227.3	25	237.0	
29th Nov.	26	235.7	26	235.7	26	235.7	24	219.1	25	227.9	
6th Dec.	27	220.5	27	220.5	27	220.5	25	212.0	25	212.0	

4.1.3	Leaf Development
 		The growth duration (days) and accumulated GDD taken by different wheat varieties for leaf development are as under:
Dates of sowing	PBW-502		PBW-343		WH-542		PBW-509		Raj-3765	
	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	
7th Nov.	85	805.8	88	837.8	86	815.8	65	650.1	65	650.1	
15th Nov.	85	760.7	87	783.4	87	783.4	70	590.0	70	590.0	
22nd Nov.	82	701.2	87	750.6	87	740.6	71	575.9	71	575.9	
29th Nov.	79	657.2	85	708.4	86	718.9	70	571.3	69	557.5	
6th Dec.	77	625.9	84	702.6	84	702.6	70	569.8	65	523.4	

		The number of days taken for leaf development stage by different wheat varieties varied under different dates of sowing. The variety PBW-343 took more number of days i.e. 88 under 7th Nov. sowing followed by WH-542 (86) and PBW-502 (85) varieties. The PBW-509 and Raj-3765 varieties took lesser (65) days under 7th Nov. sowing to complete leaf development stage. The number of days for leaf development decreased with delay in sowing from 7th Nov. to 6th Dec. in PBW-502 and PBW-343 varieties. These results are in conformity with Harding et al (1990). The accumulated GDD units decreased with delay in sowing in all varieties. PBW-343 variety took maximum (837.8) GDD units followed by WH-542 variety under 7th Nov. sowing. The Raj-3765 and PBW-509 varieties took lesser GDD units in each date of sowing as compared to other three varieties.
4.1.4	Tillering 
 		The number of days taken from sowing to tillering stage varied between variety to variety and date to date sowing. Maximum number of days taken for tillering were 78 for PBW-343 and PBW-502 varieties sown under 6th Dec. sowing. The variety PBW-509 took lesser number of days to complete the tillering stages as compared to other varieties. The number of days and accumulated GDD units taken up by different wheat varieties are given as under:
Dates of sowing	PBW-502		PBW-343		WH-542		PBW-509		Raj-3765	
	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	
7th Nov.	73	693.6	76	715.7	72	686.8	67	659.5	68	664.1	
15th Nov.	74	629.8	76	655.6	74	629.8	68	577.4	69	582.7	
22nd Nov.	73	582.9	76	632.3	73	597.9	68	540.3	72	586.4	
29th Nov.	76	635.8	78	649.4	73	607.0	65	511.6	73	607.0	
6th Dec.	78	636.1	78	636.1	74	601.4	64	512.0	68	554.1	

		The accumulated GDD units were maximum (715.7) in PBW-343 variety under 7th Nov. sowing and minimum (512.0) in PBW-509 variety under 6th Dec. sowing. The accumulated GDD units decreased with delay in sowing in variety PBW-509. These results showed that temperature effects the development of tillers. Similar results have been reported by Pal et al (1996). 
4.1.5	Stem Elongation 
		The number of days for stem elongation stage were found to be maximum (84) in PBW-343 and WH-542 varieties under 7th Nov. sowing and minimum (58) in Raj-3765 variety under 6th Dec. sowing. The number of days decreased with delay in sowing from 7th Nov. to 6th Dec. in all varieties. The number of days and accumulated GDD units taken by the crop from sowing to stem elongation are given below:
Dates of sowing	PBW-502		PBW-343		WH-542		PBW-509		Raj-3765	
	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	
7th Nov.	79	735.5	84	793.9	84	793.9	69	668.6	64	762.7	
15th Nov.	78	677.5	82	722.3	81	709.4	66	564.2	62	535.4	
22nd Nov.	76	632.3	80	681.8	81	693.1	65	506.0	60	470.0	
29th Nov.	76	635.8	80	665.8	79	657.2	63	491.1	60	453.4	
6th Dec.	75	608.4	79	646.6	79	646.6	62	485.2	58	439.3	

		The variety PBW-343 accumulate more GDD units i.e. 793.9, 722.3, 681.8, 665.8 and 646.6 from 7th Nov. to 6th Dec. sowing followed by WH-542 variety. The accumulated GDD units decreased with delay in sowing from 735.5 to 608.4 in PBW-502, from 793.9 to 646.6 in PBW-343 and WH-542, from 668.6 to 485.2 in PBW-509 and from 762.7 to 439.3 in Raj-3765 variety. 
4.1.6	Booting
		The number of days and accumulated GDD units taken by wheat varieties (PBW-502, PBW-343, WH-542, PBW-509 and Raj-3765) to complete this phenophase are given as under:
Dates of sowing	PBW-502		PBW-343		WH-542		PBW-509		Raj-3765	
	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	
7th Nov.	107	1023.1	110	1054.5	109	1043.7	86	815.8	88	837.8	
15th Nov.	106	1012.9	109	995.3	108	983.8	87	783.4	90	812.2	
22nd Nov.	106	939.3	106	939.3	102	893.7	90	764.3	88	748.5	
29th Nov.	98	853.4	100	876.7	99	864.5	89	751.5	88	739.8	
6th Dec.	92	792.2	95	832.0	92	792.2	85	713.9	85	713.9	

		The number of days to complete this phenophase decreased with delay in sowing in PBW-502, PBW-343 and WH-542 varieties. These results are in conformity with Ashwini (1982). The PBW-343 variety took maximum 110, 109, 106, 100 and 95 days under five dates of sowing (from 7th Nov. to 6th Dec.) followed by WH-542 variety. The accumulated GDD were maximum in 7th Nov. and minimum in 6th Dec. sowing in all the varieties. The maximum accumulated GDD (1054.5) were recorded in variety PBW-343 under 7th Nov. sowing followed by WH-542, PBW-502 varieties. The varieties PBW-509 and Raj-3765 accumulates lesser GDD than others.
4.1.7	Inflorescence (emergence and heading)
		The Growth duration (days) and GDD units taken to complete this stage are presented below:
Dates of sowing	PBW-502		PBW-343		WH-542		PBW-509		Raj-3765	
	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	
7th Nov.	112	1078.3	118	1145.4	115	1112.3	102	980.5	102	980.5	
15th Nov.	110	1007.1	115	1066.7	114	1053.1	99	884.8	97	865.9	
22nd Nov.	110	991.2	112	1014.5	112	1014.5	98	849.7	95	814.6	
29th Nov.	106	949.9	106	949.9	108	971.3	97	843.2	93	797.6	
6th Dec.	101	899.0	103	927.5	102	911.9	94	818.0	90	770.9	

		The number of days for this stage decreased with delay (7th Nov. to 6th Dec.) in sowing i.e. from 112 to 101 in PBW-502, 118 to 103 in PBW-343, 115 to 102 in WH-542, 102 to 94 in PBW-509 and 102 to 90 in Raj-3765 varieties. The variety PBW-343 took more (118) days in 7th Nov.  sowing followed by WH-542 (115), PBW-502 (112), PBW-509 and Raj-3765 (102) varieties. GDD accumulation was higher in variety PBW-343 (1145.4) followed by WH-542 (1112.3), PBW-502 (1078.3), PBW-509 and Raj-3765 (980.5) varieties under 7th Nov. sowing. The GDD units were decreased with delay in sowing from 7th Nov. to 6th Dec. 
4.1.8	Anthesis
		The growth duration (days) to complete the anthesis stage decreased with delay in sowing. The variety PBW-502 took 12 days and PBW-343 and WH-542 took 13 days less for anthesis under late (6th Dec.) sowing compared with normal (7th Nov.) sowing. Similar results were also reported by Singh and Ahmad (1997). The GDD units accumulated were more in variety PBW-343 (1157.9, 1104.0, 1034.7, 984.2 and 981.8) under five dates of sowing respectively. GDD units decreased with delay in sowing in all the varieties. The number of days and accumulated GDD units from sowing to anthesis are as under: 
Dates of sowing	PBW-502		PBW-343		WH-542		PBW-509		Raj-3765	
	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	
7th Nov.	115	1112.3	119	1157.9	116	1122.1	104	995.4	105	1004.2	
15th Nov.	114	1053.1	118	1104.0	116	1070.7	103	927.9	103	927.9	
22nd Nov.	114	1034.7	114	1034.7	113	1024.7	103	906.2	102	893.7	
29th Nov.	107	959.9	109	984.2	108	971.3	102	904.3	98	853.4	
6th Dec.	103	927.5	106	981.8	103	927.5	100	887.6	94	818.0	

4.1.9	Watery Ripe
		The data pertaining to the number of days and accumulated GDD to complete the watery ripe stage are given below:
Dates of sowing	PBW-502		PBW-343		WH-542		PBW-509		Raj-3765	
	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	
7th Nov.	121	1179.2	125	1231.1	120	1168.1	108	1033.6	109	1043.7	
15th Nov.	121	1136.3	122	1147.7	120	1126.3	108	983.8	108	983.8	
22nd Nov.	119	1110.7	118	1091.4	116	1059.0	106	939.3	107	951.5	
29th Nov.	109	984.2	112	1035.9	109	984.2	103	916.4	103	916.4	
6th Dec.	106	981.8	106	981.8	105	963.6	102	911.9	99	877.6	

		The number of days and accumulated growing degree days decreased from normal (7th Nov., 15th Nov. and 22nd Nov.) to late sowing (29th Nov. & 6th Dec.) in all varieties. The PBW-343 variety took maximum number of days (125) and GDD (1231.1) under 7th Nov. sowing followed by PBW-502, WH-542, Raj-3765 and PBW-509 varieties.
4.1.10	  Milky Ripe
		The data presenting the number of days and GDD units are            as under:
Dates of sowing	PBW-502		PBW-343		WH-542		PBW-509		Raj-3765	
	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	
7th Nov.	128	1264.6	129	1274.6	129	1274.6	126	1242.3	127	1254.4	
15th Nov.	127	1230.5	128	1244.6	127	1230.5	126	1212.3	126	1212.3	
22nd Nov.	125	1204.3	127	1239.3	126	1221.1	125	1204.3	117	1074.6	
29th Nov.	118	1129.5	121	1184.4	122	1205.8	118	1129.5	114	1068.2	
6th Dec.	113	1092.2	114	1112.1	118	1199.1	114	1112.1	111	1057.2	

		The number of days taken for milky ripe stage are maximum in PBW-343 and WH-542 (129) varieties and minimum in PBW-509 (126) variety under 7th Nov. sowing. The days for milky ripe (grain development) stage decreased with delay in sowing. Similar results were reported by Sharma-Natu et al (2006). The accumulated GDD units gradually decreases with delay in sowing from 7th Nov. to 6th Dec. in all the varieties. The maximum GDD units (1274.6) were observed in PBW-343 and WH-542 varieties under 7th Nov.  and minimum (1057.2) in Raj-3765 variety under                6th Dec. sowing.
4.1.11	 Soft Dough
		The number of days and accumulated GDD units taken up by wheat varieties (PBW-502, PBW-343, WH-542, PBW-509 and Raj-3765) are given below:
Dates of sowing	PBW-502		PBW-343		WH-542		PBW-509		Raj-3765	
	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	
7th Nov.	144	1520.5	140	1444.2	140	1444.2	141	1461.0	141	1461.0	
15th Nov.	138	1429.6	137	1405.4	138	1429.6	138	1429.6	138	1429.6	
22nd Nov.	136	1419.2	135	1399.4	136	1419.2	135	1399.4	136	1419.2	
29th Nov.	127	1304.9	130	1365.8	132	1407.1	128	1324.6	132	1407.1	
6th Dec.	123	1293.5	126	1356.7	126	1356.7	123	1293.5	126	1356.7	

                   The variety PBW-502 took more (144) days for soft dough stage under 7th Nov. sowing as compared to PBW-343, WH-542(140) and PBW-509, Raj-3765 (141) varieties. The number of days for soft dough stage decreases with delay in sowing. The accumulated GDD units decreases from 1520.5 to 1293.5 in PBW-502, 1444.2 to 1356.7 in PBW-343 and WH-542, 1461.0 to 1293.5 in PBW-509 and from 1461.0 to 1356.7 in Raj-3765 varieties with delay in sowing from 7th Nov. to 6th Dec.
4.1.12	  Hard Dough
		The number of days and accumulated GDD units for hard dough decreased with delay in sowing in all varieties. The variety PBW-343 took maximum days (158) and GDD units (1813.4) to complete this phenophase under 7th Nov. sowing followed by WH-542 variety. The variety PBW-502 took 168.3, PBW-343 took 116.9, WH-542 took 94.5, PBW-509 took 192.5 and Raj-3765 took 103.9 GDD less for hard dough stage under 6th Dec. sowing compared with 7th Nov. sowing.  The growth duration (days) and GDD units taken by five wheat varieties are given as under: 
Dates of sowing	PBW-502		PBW-343		WH-542		PBW-509		Raj-3765	
	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	
7th Nov.	156	1765.7	158	1813.4	156	1765.7	156	1765.7	153	1701.3	
15th Nov.	151	1700.0	153	1751.6	153	1751.6	151	1700.0	149	1650.6	
22nd Nov.	145	1624.2	149	1720.3	150	1744.5	145	1624.2	146	1650.0	
29th Nov.	140	1603.5	145	1717.7	145	1717.7	139	1575.2	140	1603.5	
6th Dec.	136	1597.4	140	1696.5	139	1671.2	135	1573.2	136	1597.4	

4.1.13	 Physiological Maturity
		The growth duration (days) and accumulated GDD units taken by five wheat varieties from sowing to complete maturity are given below:
Dates of sowing	PBW-502		PBW-343		WH-542		PBW-509		Raj-3765	
	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	DAS	GDD	
7th Nov.	160	1864.1	162	1918.2	160	1864.1	160	1864.1	159	1838.3	
15th Nov.	155	1799.7	156	1821.9	156	1821.9	155	1799.7	154	1779.9	
22nd Nov.	149	1720.3	153	1818.3	153	1818.3	148	1698.1	149	1720.3	
29th Nov.	144	1693.7	149	1817.5	149	1817.5	142	1645.5	143	1669.7	
6th Dec.	139	1671.2	142	1745.2	142	1745.2	138	1645.4	138	1645.4	

		The variety PBW-343 took more number of days (162) under 7th Nov. sowing followed by PBW-502, WH-542, PBW-509 and Raj-3765 varieties. The number of days for maturity under 7th Nov. sowing ranges from 162 to 159 days and 142 to 138 days under 6th Dec. sowing. The number of days decreased with delay in sowing. Late sown wheat crop is generally exposed to high temperature stress resulting in shortening of reproductive (booting to anthesis) and ripening (Anthesis to maturity) phases. Similar results were reported by Abrol and Ingram (1996) and Nagarajan and Rane (2002). Randhawa et al (1992) also reported that reproductive period is shortened under late sowing conditions because temperature starts rising and late sown crop is forced to accumulate rapid GDD in lesser number of days.
		The accumulated GDD units for the completion of entire growth period decreased in all varieties with delay in sowing from 7th Nov. to 6th Dec. The variety PBW-343 took maximum GDD units (1918.2) under 7th Nov. sowing for complete growth period followed by WH-542, PBW-502, PBW-509 and Raj-3765 varieties. By delay in sowing from 7th Nov. to 6th Dec., the decline in grain yield was found to be 37.9% and decrease in number of days and GDD were 12.34% and 9.0% respectively in PBW-343 variety. In PBW-502 variety, the decline in grain yield from 7th Nov. to 6th Dec. was 34.4% and decrease in number of days and GDD were 13.1% and 10.3% respectively. The decline in rate of grain yield in WH-542 variety was 36.5% from 7th Nov. to 6th Dec. sowing. The number of days and GDD units were also decreased by 11.25% and 6.4% respectively. In PBW-509 variety, the number of days and GDD units decreased by 13.75% & 11.73% from 7th Nov. to 6th Dec. sowing. The decline in grain yield was observed to be 28.9%. The grain yield was decreased by 33.2% from7th Nov. to 6th Dec.sowing in variety Raj-3765. The number of days and GDD units were also decreased by 13.2% and 10.49% respectively. So high temperature during late sowing hastens the phenologicaldevelopment of crop, reduces the total duration of crop growth, grain filling and finally lowering the grain yield (Wang et al 1992). The grain yield decreases with increase in temperature prevailing in late sowing conditions due to decrease in dry matter accumulation in the panicle at ripening period (Saitoh et al 2006).The GDD accumulated more during reproductive stage than from vegetative stages in all the varieties.
4.2	PHYSIOLOGICAL TRAITS 
		Physiological traits affecting grain yield recorded at different growth stages are discussed under the following headings:
4.2.1	Emergence Count  m-2  
4.2.2	Number of Tillers m-2
4.2.3	Leaf Area Index at 90 days after sowing
4.2.4	Crop Growth Rate (mg cm-2 day-1) at 90-120 DAS
4.2.5	Pre-anthesis Dry Matter Production (%)
4.2.6	Total number of Leaves on Main Shoot at booting stage
4.2.7	Spike Weight at Anthesis 
4.2.8	Partitioning to Spike at Anthesis stage
4.2.9	Grain Filling Rate (mg grain-1 day-1)
4.2.10	 Grain Growth Duration (days)
4.2.11	 Plant Height at Maturity
4.2.1	Emergence Count 
		The data on emergence count of five wheat varieties under five dates of sowing are given in Table 4.6.
Table 4.6	Emergence count m-2 in different wheat varieties under different dates of sowing. 

Variety 	7th Nov. 	15th Nov. 	22nd Nov. 	29th Nov. 	6th Dec. 	Mean	
PBW-502 	125.67	113.00	115.00	101.67	96.00	110.27	
PBW-343 	121.00	108.67	112.67	108.00	106.00	111.27	
WH-542 	113.00	105.33	108.00	96.00	93.33	103.13	
PBW-509 	110.00	107.00	107.33	99.67	92.67	103.33	
Raj-3765 	104.67	106.33	106.67	98.67	92.67	101.80	
Mean	114.87	108.07	109.93	100.80	96.13		
CD (P = 0.05)    Dates (D) = 2.71 	    Varieties (V) =  1.61 	 D x V =  3.61

		The normal (7th Nov.) date of sowing has maximum emergence count (114.87) and minimum (96.13) in late (6th Dec.) sowing. The 15th Nov. and 22nd Nov. dates of sowing does not differ from each other. Emergence count decreases with delay in sowing. The variety PBW-343 has more emergence count(111.27) followed by PBW-502 variety (110.27). The varieties PBW-343 and WH-542 showed significant differences in emergence count. The interaction of normal (7th Nov.) and late (6th Dec.) date of sowing with all varieties for this character was found to be significant.
4.2.2	Number of Tillers (m-2)
		Number of tillers were maximum in 7th Nov. sowing (637.93) and it gradually decreases withy delay in sowing from 15th Nov. (634.47) to 6th Dec. (530.87). The differences between dates of sowing were found to be significant (Table 4.7). Similar findings were recorded by Girothia et al (1987).
Table 4.7	Number of tillers m-2 in wheat varieties under different dates of sowing. 

Variety 	7th Nov. 	15th Nov. 	22nd Nov. 	29th Nov. 	6th Dec. 	Mean	
PBW-502 	686.00	662.00	648.33	602.00	582.00	636.07	
PBW-343 	712.33	689.00	650.33	610.00	575.33	647.40	
WH-542 	690.00	668.67	625.00	590.33	559.00	626.60	
PBW-509 	505.00	560.67	542.00	510.33	462.67	516.13	
Raj-3765 	596.33	592.00	584.00	550.33	475.33	559.60	
Mean	637.93	634.47	609.93	572.60	530.87		
CD (P = 0.05)   Dates (D) = 2.48 	  Varieties (V) =  1.85 	 D x V =  4.14

		All the varieties differed significantly in producing the number of tillers. PBW-343 variety produced more number of tillers (647.40) followed by PBW-502, WH-542, Raj-3765 and PBW-509 varieties. The interaction of 22nd Nov., 29th Nov. and 6th Dec. sowing with all varieties was significant.
4.2.3	Leaf Area Index 
		Data presented in Table 4.8 showed that there was significant reduction in Leaf area index with each delay in sowing from 7th Nov. to 6th Dec. The maximum leaf area index (10.30) was recorded in 7th Nov. sowing and then decreased thereafter. The minimum leaf area index (7.06) was observed in case of 6th Dec. sowing. Significant reduction in leaf area index were also reported by Ashraf and Bhatti (1998).
Table 4.8	Leaf area index at 90 days after sowing in wheat varieties under different dates of sowing. 

Variety 	7th Nov. 	15th Nov. 	22nd Nov. 	29th Nov. 	6th Dec. 	Mean	
PBW-502 	10.34	9.22	8.03	7.83	7.02	8.49	
PBW-343 	10.61	9.24	8.03	7.83	7.04	8.55	
WH-542 	9.71	7.85	7.46	6.95	6.55	7.71	
PBW-509 	10.51	10.02	8.97	8.41	7.63	9.11	
Raj-3765 	10.34	9.21	8.35	8.16	7.04	8.62	
Mean	10.30	9.11	8.17	7.84	7.06		
CD (P = 0.05)  Dates (D) = 0.07 	       Varieties (V) =  0.04 	 D x V =  0.09

		All the varieties differed significantly as far as the leaf area index was concerned. The variety PBW-509 has maximum leaf area index (9.11) followed by Raj-3765, PBW-343, PBW-502 and WH-542. The interaction of all varieties with 7th Nov. and 6th Dec. sowing showed significant differences.

4.2.4	Crop Growth Rate 

		Crop growth rate increased significantly with delay in sowing from 7th Nov. to 6th Dec. Because temperature started rising with delay in sowing and large number of GDD units get accumulated in lesser days, resulting in higher crop growth rate. The data on crop growth rate for different wheat varieties under five dates of sowing are given in Table 4.9.
Table 4.9	Crop growth rate (mg cm-2 day-1 ) at 90-120 days after sowing in different wheat varieties under different dates of sowing. 

Variety 	7th Nov. 	15th Nov. 	22nd Nov. 	29th Nov. 	6th Dec. 	Mean	
PBW-502 	4.47	5.00	5.33	5.57	5.93	5.26	
PBW-343 	6.43	6.60	6.97	6.90	6.83	6.75	
WH-542 	5.40	6.20	6.13	6.43	6.77	6.19	
PBW-509 	5.27	5.20	5.33	5.67	6.03	5.50	
Raj-3765 	5.20	6.13	6.20	6.57	6.67	6.15	
Mean	5.35	5.83	5.99	6.23	6.45		
CD (P = 0.05)   Dates (D) = 0.12 	       Varieties (V) =  0.13 	 D x V =  0.30

		The variety PBW-343 has more CGR (6.75) followed by WH-542 (6.19). The varieties WH-542 and Raj-3765 showed non-significant differences in crop growth rate. Interaction of PBW-343 and PBW-509 varieties with all dates of sowing showed significant differences. 
4.2.5	Pre-anthesis Dry Matter Production 
		The data on pre-anthesis dry matter production of five wheat varieties under five dates of sowing are given in Table 4.10.
Table 4.10	Pre-anthesis dry matter production (%) in five wheat varieties under five dates of sowing.

Variety 	7th Nov. 	15th Nov. 	22nd Nov. 	29th Nov. 	6th Dec. 	Mean	
PBW-502 	51.07	52.37	57.00	51.73	50.43	52.52	
PBW-343 	64.13	63.97	64.17	55.47	52.03	59.95	
WH-542 	62.57	55.27	50.03	49.27	49.73	53.37	
PBW-509 	65.27	56.33	55.70	53.87	52.53	54.04	
Raj-3765 	63.47	55.47	50.70	50.67	49.93	56.74	
Mean	61.30	56.68	55.52	52.20	50.93		
CD (P = 0.05)  Dates (D) = 2.11 	       Varieties (V) =  1.45 	 D x V =  3.24
		The maximum pre-anthesis dry matter production (61.30%) was observed under 7th Nov. sowing and then it gradually decreases with delay in sowing. The differences between 7th Nov. and 6th Dec. sowing were found to be significant. Results of Sarkar et al (1987) confirmated our findings regarding decrease in dry matter production with delay in sowing. re-anthesis dry matter production was found to be maximum i.e. (59.95%) in variety PBW-343 followed by Raj-3765 (56.74%) variety. The wheat varieties PBW-343 and WH-542 differed significantly from each other. The interaction of PBW-343 and Raj-3765 varieties with late sowing (6th Dec.) showed significant differences.
4.2.6	Total number of Leaves on Main Shoot 
		Total number of leaves on main shoot at booting stage of wheat varieties under different dates of sowing are given in Table 4.11.

Table 4.11	Total number of leaves on main shoot at booting stage in wheat varieties under different dates of sowing. 

Variety 	7th Nov. 	15th Nov. 	22nd Nov. 	29th Nov. 	6th Dec. 	Mean	
PBW-502 	4.00	4.00	5.00	6.00	5.00	4.80	
PBW-343 	6.00	6.00	6.00	6.33	6.00	6.07	
WH-542 	6.00	6.00	6.00	6.33	6.00	6.07	
PBW-509 	4.00	4.00	4.00	5.00	5.00	4.40	
Raj-3765 	5.00	6.00	5.33	6.33	6.00	5.73	
Mean	5.00	5.20	5.27	6.00	5.60		
CD (P = 0.05)   Dates (D) = 0.28 	       Varieties (V) =  0.13 	 D x V =  0.30

		Number of leaves on main shoot increases with delay in sowing  and found to be maximum (6 leaves) under 29th Nov. sowing. Similar findings were reported by Singh and Pal (2003). The differences between 7th Nov. and 29th Nov. sowing were found to be significant. The varieties PBW-343 and WH-542 produced more leaves as compared to other varieties and they does not differ from each other.  The interaction of PBW-509 variety with 7th Nov. and 29th Nov. sowing was found to be significant. 
4.2.7	Spike Weight at Anthesis
		Spike dry matter at anthesis reflects the peak quantity of assimilates invested in reproductive growth. Spike weight at anthesis in wheat varieties under different dates of sowing are given in Table 4.12. Spike weight (gm) was found to be maximum i.e. 0.71 gm in normal (15th Nov.) sowing and minimum (0.46 gm) in late (6th Dec.) sowing. The dates of sowing differed significantly from each other.
Table 4.12	Spike weight at anthesis in different wheat varieties under different dates of sowing.

Variety 	7th Nov. 	15th Nov. 	22nd Nov. 	29th Nov. 	6th Dec. 	Mean	
PBW-502 	0.60	0.63	0.53	0.63	0.50	0.58	
PBW-343 	0.70	0.87	0.67	0.57	0.47	0.65	
WH-542 	0.67	0.50	0.60	0.60	0.40	0.55	
PBW-509 	0.60	0.80	0.50	0.50	0.57	0.59	
Raj-3765 	0.57	0.77	0.43	0.73	0.37	0.57	
Mean	0.63	0.71	0.55	0.61	0.46		
CD (P = 0.05)  Dates (D) = 0.04 	       Varieties (V) =  0.03 	 D x V =  0.07

		The variety PBW-343 has more spike weight (0.65 gm) followed by PBW-509 variety. The varieties PBW-343 and WH-542 differed significantly. Dogiwal et al (2004) observed a significant positive correlation of spike weight at anthesis with grain yield. The interaction of normal (15th Nov.) and late (6th Dec.) sowing with all varieties showed significant differences.
4.2.8	Partitioning to Spike at Anthesis Stage
		Cultivar PBW-343 has more partitioning to spike than other varieties in each date of sowing. The cvs. PBW-502, PBW-343 and WH-542 differed significantly from each other. The interaction of all varieties with 6th Dec. sowing was observed to be significant. Tyagi et al (2004) reported that total dry matter as well as its partitioning to spike reduced significantly at anthesis stage under late sowing as compared with normal date of sowing. Partitioning to spike revealed that there was significant reduction in partitioning with delay in sowing (Table 4.13).
Table 4.13	Partitioning to spike (g) at anthesis stage in different wheat varieties under different dates of sowing. 

Variety 	7th Nov. 	15th Nov. 	22nd Nov. 	29th Nov. 	6th Dec. 	Mean	
PBW-502 	0.32	0.29	0.25	0.23	0.22	0.26	
PBW-343 	0.35	0.33	0.34	0.29	0.23	0.31	
WH-542 	0.34	0.32	0.30	0.28	0.23	0.29	
PBW-509 	0.29	0.27	0.24	0.21	0.20	0.24	
Raj-3765 	0.31	0.28	0.25	0.23	0.21	0.25	
Mean	0.32	0.30	0.28	0.25	0.22		
CD (P = 0.05)   Dates (D) = 0.015           Varieties (V) =  0.010     D x V =  0.023

4.2.9	Grain Filling Rate 
		The highest average rate of grain filling was 1.87mg/grain/day under late (6th Dec.) sowing. The rate of grain filling sown on different dates varied significantly. The grain filling rate at different stages during grain filling also varied significantly. The peak rate of grain filling was recorded on 40 days after anthesis in 7th Nov. sowing and 30 days after anthesis in 15th Nov., 22nd Nov. and 6th Dec. sowing. Cultivar PBW-343 has maximum grain filling rate (1.28 mg/grain/day) followed by cvs. PBW-502, WH-542, PBW-509 and Raj-3765. The grain filling rate in wheat varieties at different stages are given in Table 4.14.

Table 4.14	Rate of grain filling (mg/grain/day) in wheat varieties at different stages of grain development under five dates of sowing 

Days after anthesis (DAA)		                      DOS   7th November	
	PBW-502 	PBW-343 	WH-542 	PBW-509 	Raj-3765 	Mean	
10	0.71	0.75	0.69	0.65	0.64	0.69	
20	1.18	1.19	1.15	1.12	1.09	1.15	
30	1.27	1.29	1.25	1.19	1.17	1.23	
40	1.36	1.40	1.38	1.36	1.35	1.37	
50	1.11	1.14	1.13	1.08	1.11	1.11	
Mean	1.13	1.15	1.12	1.08	1.07		
CD (P = 0.05)   Varieties (V) =  0.008         DAA  =  0.007       V x DAA =  0.017
	15th November	
10	0.64	0.64	0.59	0.61	0.58	0.61	
20	1.31	1.36	1.35	1.36	1.34	1.34	
30	1.39	1.45	1.40	1.40	1.38	1.40	
40	1.20	1.21	1.18	1.16	1.14	1.14	
Mean	1.13	1.16	1.13	1.13	1.11		
CD (P = 0.05)   Varieties (V) =  0.008         DAA  =  0.007       V x DAA =  0.015
	22nd November	
10	0.13	0.18	0.16	0.10	0.09	0.13	
20	1.17	1.28	1.24	1.16	1.10	1.19	
30	1.64	1.71	1.68	1.61	1.63	1.65	
40	1.58	1.64	1.59	1.56	1.57	1.59	
Mean	1.13	1.20	1.16	1.10	1.09		
CD (P = 0.05)   Varieties (V) =  0.009         DAA  =  0.007       V x DAA =  0.015

	29th November	
10	0.36	0.38	0.32	0.35	0.37	0.36	
20	1.23	1.31	1.30	1.25	1.28	1.27	
30	1.81	1.83	1.81	1.79	1.76	1.80	
40	1.62	1.60	1.55	1.48	1.46	1.54	
Mean	1.28	1.28	1.24	1.22	1.21		
CD (P = 0.05)   Varieties (V) =  0.014         DAA  =  0.005       V x DAA =  0.012
	6th December	
10	0.54	0.55	0.52	0.46	0.49	0.52	
20	1.17	1.24	1.22	1.16	1.15	1.19	
30	1.90	1.90	1.89	1.86	1.83	1.87	
40	1.30	1.36	1.35	1.29	1.27	1.31	
Mean	1.23	1.26	1.24	1.20	1.18		
CD (P = 0.05)   Varieties (V) =  0.009         DAA  =  0.008       V x DAA =  0.017
		                                                                                        
		All the varieties differed significantly in their grain filling rate under 6th Dec. sowing. The interaction of all the varieties with different stages of grain development under late (6th Dec.) sowing showed significant differences. An increase in the rate of grain filling with a rise in temperature above 200C is commonly observed by Zahedi et al (2003).
4.2.10  Grain Growth Duration 
		The maximum grain growth duration (47.73 days) was found in 7th Nov. sowing and after that there was significant reduction with delay in sowing. The average growth duration of grain filling in wheat varieties under different dates of sowing are given in Table 4.15.
Table 4.15	Grain growth duration (days) from anthesis to maturity in wheat varieties under different dates of sowing .

Variety 	7th Nov. 	15th Nov. 	22nd Nov. 	29th Nov. 	6th Dec. 	Mean	
PBW-502 	43.00	41.00	35.67	36.67	37.00	38.67	
PBW-343	44.33	39.33	39.00	40.00	36.67	39.87	
WH-542 	42.00       	39.33	40.00	40.00	38.00	39.87	
PBW-509 	56.67	52.00	46.00	39.67	38.67	46.60	
Raj-3765 	52.67	50.33	47.00	43.67	42.67	47.27	
Mean	47.73	44.40	41.53	40.00	38.60		
CD (P = 0.05)   Dates (D) = 0.94 	       Varieties (V) =  0.77 	 D x V =  1.71

		The variety Raj-3765 had longest grain growth duration i.e. 47.27 days followed by PBW-509, PBW-343, WH-542 and PBW-502 varieties. The difference between PBW-343 and WH-542 varieties was non-significant. The interaction of all varieties with normal (15th Nov.) sowing showed significant differences. The duration of grain filling in wheat is decreased by high temperature (Slafer et al 1996 and Randhawa et al 1992).
4.2.11	 Plant height
		Plant height of variety PBW-343 was maximum (86.51 cm) followed by WH-542. The varieties PBW-343, PBW-502 and Raj-3765 differed significantly from each other in plant height. The dates of sowing and varieties interaction showed significant differences. Similar results were reported by Jain et al (1992). Data presented in Table 4.16 revealed that plant height decreases significantly with delay in sowing. It was found to be maximum (89.02 cm) in 7th Nov. sowing.
Table 4.16	Plant height (cm) at maturity in different wheat varieties under different dates of sowing. 

Variety 	7th Nov. 	15th Nov. 	22nd Nov. 	29th Nov. 	6th Dec. 	Mean	
PBW-502 	82.37	79.27	79.30	81.37	80.70	80.60	
PBW-343	97.33	94.17	83.17	80.03	77.87	86.51	
WH-542 	95.40	94.37	82.43	80.40	79.07	86.33	
PBW-509 	87.53	84.23	86.07	84.57	83.23	85.13	
Raj-3765 	82.47	91.03	82.37	79.43	77.67	82.59	
Mean	89.02	88.61	82.67	81.16	79.71		
CD (P = 0.05)   Dates (D) = 0.54 	       Varieties (V) =  0.27 	 D x V =  0.60

4.3	YIELD AND YIELD CONTRIBUTING ATTRIBUTES
		The important yield contributing attributes are discussed as under:
4.3.1	Effective Tillers m-2/ Number of Spike m -2
4.3.2	Number of Grains/Spike
4.3.3	Grain-Spike Weight Ratio
4.3.4	1000-Grain Weight (gm)
4.3.5	Biological Yield (q/ha)
4.3.6	Grain Yield (q/ha)
4.3.7	Harvest Index (HI)
4.3.8	Regression Equations 
4.3.9	Correlation and Path Coefficient Analysis 

4.3.1	Effective Tillers / Number of Spike m-2
		Number of Productive ears were found to be maximum (513.53) in normal (15th Nov.) sowing and then gradually decreases with delay in sowing. The 7th Nov. and 6th Dec. sowing showed significant differences. The number of effective tillers per square metre at maturity are enlisted in Table 4.17. 
Table 4.17	Effective tillers/Number of spike m-2 in wheat varieties under different dates of sowing.

Variety 	7th Nov. 	15th Nov. 	22nd Nov. 	29th Nov. 	6th Dec. 	Mean	
PBW-502 	517.00	510.00	487.67	449.33	430.00	478.80	
PBW-343	578.33	551.00	520.33	489.33	479.00	523.60	
WH-542 	527.33	526.67	501.00	473.67	465.33	498.80	
PBW-509 	370.00	487.67	457.33	418.33	368.00	420.27	
Raj-3765 	456.33	492.33	470.33	435.33	397.33	450.33	
Mean	489.80	513.53	487.33	453.20	427.93		
CD (P = 0.05)   Dates (D) = 2.32	       Varieties (V) =  2.35 	 D x V =  5.25

		All the varieties differed significantly in producing the number of effective tillers. The variety PBW-343 produced more number of effective tillers in each date of sowing as compared with other varieties. The decrease in effective tillers seems to be associated with initial plant density under late sowing (Singh and Ahmad 1997). The interaction of 7th Nov., 15th Nov., 22nd Nov. and 6th Dec. sowing with all varieties are significant. Similar findings were reported by Akhtar et al (2006).

4.3.2	Number of Grains per Spike
		Number of grains per spike in wheat varieties under different dates of sowing are given in Table 4.18.
Table 4.18	Number of grains per spike in wheat varieties under different dates of sowing.

Variety 	7th Nov. 	15th Nov. 	22nd Nov. 	29th Nov. 	6th Dec. 	Mean	
PBW-502 	55.33	53.33	48.00	45.67	41.33	48.73	
PBW-343	59.33	57.67	50.67	47.67	43.00	51.67	
WH-542 	64.67	62.00	57.67	51.00	47.00	56.47	
PBW-509 	49.67	43.00	39.67	36.67	36.33	41.07	
Raj-3765 	52.67	49.33	45.33	43.33	40.67	46.27	
Mean	56.33	53.07	48.27	44.87	41.67		
CD (P = 0.05)  Dates (D) = 1.38 	       Varieties (V) =  1.02 	 D x V =  2.28

		The 7th Nov. sowing has maximum grains per spike (56.33). The number of grains per spike decreases with delay in sowing. Maximum reduction in number of grains/spike by delayed sowing may be due to greater reduction in the reproductive growth phase (spike initiation to anthesis). The different dates of sowing gave significantly different number of grains per spike. Varieties WH-542 and PBW-343 produced more i.e. 56.47 and 51.67 grains per spike respectively. WH-542 variety has maximum number of grains per spike. All the varieties significantly differed from each other. The interaction of PBW-343, WH-542 and PBW-509 varieties with 22nd Nov. and 29th Nov. sowing for this character was significant. Similar results were reported by Singh and Pal (2003).
4.3.3	Grain-Spike Weight Ratio
		Grain-Spike weight ratio is the desirable characteristic for potential yield in wheat varieties. The data on Grain-spike weight ratio are enlisted in Table 4.19. 
Table 4.19	Grain-spike weight ratio in different wheat varieties under different dates of sowing.

Variety 	7th Nov. 	15th Nov. 	22nd Nov. 	29th Nov. 	6th Dec. 	Mean	
PBW-502 	0.75	0.70	0.70	0.69	0.70	0.71	
PBW-343	0.76	0.74	0.75	0.72	0.71	0.74	
WH-542 	0.75	0.74	0.72	0.73	0.70	0.73	
PBW-509 	0.73	0.68	0.70	0.69	0.69	0.70	
Raj-3765 	0.75	0.70	0.69	0.70	0.68	0.70	
Mean	0.75	0.71	0.71	0.70	0.70		
CD (P = 0.05)  Dates (D) = 0.022	       Varieties (V) =  0.009 	 D x V =  0.020

		The data showed that maximum grain-spike weight ratio i.e. 0.75 was observed under 7th Nov. sowing. The normal (7th Nov.) and late (6th Dec.) sowing significantly differed from each other. Variety PBW-343 has maximum grain-spike weight ratio (0.74) followed by WH-542 (0.73) variety. The varieties Raj-3765 and PBW-509 does not differ from each other. The interaction of all the varieties with 7th Nov. sowing showed significant difference. 
4.3.4	1000-Grain Weight 
		The 1000-grain weight also showed significant variability due to change in sowing date, genotype and their interaction (Table 4.20).
Table 4.20	1000-grain weight (gm) in different wheat varieties under different dates of sowing .

Variety 	7th Nov. 	15th Nov. 	22nd Nov. 	29th Nov. 	6th Dec. 	Mean	
PBW-502 	34.14	31.53	31.72	28.09	26.89	30.47	
PBW-343	37.02	34.39	33.30	30.36	29.96	33.01	
WH-542 	36.84	33.57	32.17	29.11	28.15	31.97	
PBW-509 	32.00	28.39	27.29	26.51	25.76	27.99	
Raj-3765 	33.90	30.50	28.99	27.25	26.38	29.41	
Mean	34.78	31.68	30.70	28.26	27.43		
CD (P = 0.05)    Dates (D) = 0.19 	       Varieties (V) =  0.17 	 D x V =  0.38

		The maximum 1000 grain weight (34.78 g) was observed in 7th Nov. sowing. Thereafter, a decreasing trend was observed up to 6th Dec. sowing. The difference between different dates of sowing were found to be significant. Sarkar et al (1987) and Samre et al (1989) also observed decrease in 1000-grain weight, resulting in lower grain yield under delayed sowing. The PBW-343 variety produced more 1000-grain weight (33.01 g) followed by WH-542 (31.97 g), PBW-502 (30.47 g) varieties. All the varieties differed significantly in producing 1000-grain weight. Variety PBW-343 recorded higher test weight thereby showed a greater degree of tolerance to high post anthesis temperature. The better performance of this genotype revealed the existence of sink tolerance mechanism. A similar result was also reported by Jenner (1991). The interaction between 7th Nov. and 6th Dec. with PBW-502, WH-542 and Raj-3765 varieties was significant. 
4.3.5	Biological Yield
		The biological yield of different wheat varieties under five dates of sowing are given in Table 4.21.
Table 4.21	Biological yield (q/ha) in the wheat varieties under different dates of sowing. 

Variety 	7th Nov. 	15th Nov. 	22nd Nov. 	29th Nov. 	6th Dec. 	Mean	
PBW-502 	156.67	143.33	130.00	131.67	109.67	134.27	
PBW-343	178.33	168.33	158.33	140.00	116.67	152.33	
WH-542 	180.00	160.00	140.00	130.00	110.00	144.00	
PBW-509 	121.67	114.67	110.00	106.67	98.67	110.33	
Raj-3765 	140.00	126.33	118.33	114.67	99.50	119.77	
Mean	155.33	142.33	131.33	124.60	106.90		
CD (P = 0.05)    Dates (D) = 1.79	       Varieties (V) =  2.21 	 D x V =  4.93

		There was significant reduction in the biological yield with delay in sowing from 7th November to 6th December. The highest biological yield (155.33 q/ha) was observed in 7th November sowing. The rate of decline in biological yield with delay in sowing from 7th to 15th Nov. was 8.37%, from 15th to 22nd Nov. (7.73%), 22nd to 29th Nov. (5.10%) and from 29th Nov. to 6th Dec. was 14.20%. Genotypes showed significant variation in terms of biological yield under different dates of sowing.  The variety PBW-343 produced higher biological yield (152.33) followed by WH-542 (144.00), PBW-502 (134.27), Raj-3765 (119.77) and PBW-509 (110.33) varieties. The interaction of 6th Dec. sowing with all varieties was significant. Dogiwal et al (2004) also observed similar result.
4.3.6	Grain Yield
		The grain yield of different wheat varieties are given in             Table 4.22.  
Table 4.22	Grain yield (q/ha) in different wheat varieties under different dates of sowing. 

Variety 	7th Nov. 	15th Nov. 	22nd Nov. 	29th Nov. 	6th Dec. 	Mean	
PBW-502 	45.63	41.48	40.40	32.50	29.92	37.98	
PBW-343	51.40	47.60	44.85	36.55	31.92	42.46	
WH-542 	47.62	43.80	43.04	33.41	30.24	39.62	
PBW-509 	38.91	34.97	38.46	30.34	27.67	34.07	
Raj-3765 	43.60	39.50	39.01	31.36	29.14	36.52	
Mean	45.43	41.47	41.15	32.83	29.78		
CD (P = 0.05)   Dates (D) = 0.81	       Varieties (V) =  0.60 	 D x V =  1.33

		There is reduction in grain yield with delay in sowing from 7th Nov. to 6th Dec.  The rate of decline from normal (7th Nov.) to late sowing (6th Dec.) was relatively high i.e. 34.44%.  The 15th Nov. and 22nd Nov. sowing does not differ from each other.  The varieties differed significantly from each other in grain yield.  The maximum grain yield (42.46 q/ha) was observed in PBW-343 variety followed by WH-542 (39.62) variety.  The decrease in grain yield from normal (7th Nov.) to late (6th Dec.) sowing was 34.43% in PBW-502, 37.89% in PBW-343, 36.49% in WH-542, 28.89% in PBW-509 and 33.16% in Raj-3765 variety. The varieties and date of sowing interaction for grain yield was significant. The adverse effect of high temperature during late sowing on grain yield was also reported by Wahid et al (2007) and Warrington et al  (1977).
4.3.7	Harvest Index 
 		The data in Table 4.23 regarding Harvest Index revealed that HI was found maximum (31.63) in normal (22nd Nov.) date of sowing. Harvest index decreases with delay in sowing and found minimum in late i.e. 29th Nov. sowing. The 7th Nov. and 6th Dec. sowing differed significantly from each other.
Table 4.23	Harvest index (HI) in different wheat varieties under different dates of sowing. 

Variety 	7th Nov. 	15th Nov. 	22nd Nov. 	29th Nov. 	6th Dec. 	Mean	
PBW-502 	29.12	28.94	31.11	24.68	27.28	28.23	
PBW-343	28.84	28.28	28.33	26.13	27.36	27.79	
WH-542 	26.46	27.37	30.77	25.70	27.54	27.57	
PBW-509 	31.99	30.50	34.96	28.46	28.04	30.79	
Raj-3765 	31.16	31.27	32.98	27.36	29.29	30.41	
Mean	29.52	29.27	31.63	26.47	27.90		
CD (P = 0.05)    Dates (D) = 0.60	       Varieties (V) =  0.66 	 D x V =  1.47

		The variety PBW-509 has maximum harvest index (30.79) followed by Raj-3765 variety. The varieties PBW-343 and PBW-509 differed significantly from each other. The interaction of PBW-502, PBW-343 and WH-542 varieties with 22nd Nov. sowing showed significant differences. The decrease in Harvest Index (HI) indicate that grain mass was more affected than biomass under late sowing (Sharma-Natu et al 2006).
4.3.8	Regression Equations 
		The regression equations in wheat are discussed under the following headings :
4.3.8.1 Growth duration (Days)
4.3.8.2 Growing degree days (GDD)
4.3.8.1 Growth Duration (Days)
		The regression equation for grain yield and growth duration are presented in Table 4.24.  
Table 4.24	Relationship between grain yield (Y) and growth duration (X) during different phenophases of wheat.

Sr. No.	Growth stages	Regression equation	r	
1.	Seedling emergence	Y= 80.24-6.26x	0.749	
2.	Crown root initiation	Y= 71.07-1.36x	0.371	
3.	Leaf development	Y= 11.44+0.34x	0.444	
4.	Tillering	Y= 9.40+0.398x	0.245	
5.	Stem elongation	Y= 19.04+0.260x	0.365	
6.	Booting	Y= 8.19+0.314x	0.518	
7.	Inflorescence (emergence & heading)	Y= -5.37+0.417x	0.528	
8.	Anthesis	Y= -41.32+0.738x	0.785	
9.	Watery ripe	Y= -47.46+0.769x	0.834	
10.	Milky ripe	Y= -75.18+0.926x	0.799	
11.	Soft dough	Y= -78.65+0.871x	0.810	
12.	Hard dough	Y= -89.43+0.869x	0.903	
13.	Physiological maturity	Y= -84.07+0.812x	0.895	

		That data in Table 4.24 showed a significant positive correlation between grain yield and growth duration during seedling emergence, anthesis, watery ripe, milky ripe, soft dough, hard dough and maturity stages. The highest value was obtained with the growth duration during hard dough (r=0.903), physiological maturity (r=0.895) and watery ripe (r = 0.834). Soft dough (r=0.810), milky ripe (r=0.799), anthesis (r=0.785) and seedling emergence (r=0.749) stages.  High temperature increases the growth rate but it decreases the growth (sowing to anthesis and anthesis to maturity) durations which in turn reduces the grain yield (Singh and Pal 2003).
4.3.8.2  Growing Degree Days (GDD)
		The regression equation indicating the relationship of grain yield with GDD units accumulated during different phenophases of wheat are presented in Table 4.25. Regression analysis indicated a significant positive correlation between grain yield and GDD accumulated during grain ripening stages. The highest value was obtained under watery ripe (r=0.854), hard dough (r=0.849), anthesis (r=0.)833, physiological maturity (r=0.815), crown root initiation (r=0.738), milky ripe (r=0.715), soft dough (r=0.707) and seedling emergence (r=0.667) stages.  It confirmed the result of Pahwa (2002) that grain yield in wheat increased by 14 q/ha for an increase of 100 GDD units during ripening phase of grains. 

Table 4.25	Relationship between grain yield (Y) and growing degree days (X) accumulated during different growth stages of wheat.

Sr. No.	Growth stages	Regression equation	r	
1.	Seedling emergence	Y= 0.911+0.34x	0.667	
2.	Crown root initiation	Y= -8.79+0.13x	0.738	
3.	Leaf development	Y= 3.12+0.03x	0.650	
4.	Tillering	Y= -20.48+0.06x	0.608	
5.	Stem elongation	Y= 9.87+0.028x	0.585	
6.	Booting	Y= 5.61+0.025x	0.635	
7.	Inflorescence (emergence & heading)	Y= -8.16+0.032x	0.648	
8.	Anthesis	Y= -29.36+0.044x	0.833	
9.	Watery ripe	Y= -32.26+0.044x	0.854	
10.	Milky ripe	Y= -51.39+0.050x	0.715	
11.	Soft dough	Y= -69.75+0.052x	0.707	
12.	Hard dough	Y= -101.5+0.058x	0.849	
13.	Physiological maturity	Y= -82.5+0.048x	0.815	

4.3.9	Correlation and Path Coefficient Analysis of Yield and Physiological Traits in Wheat under different dates of sowing

		It is evident from data given in Table 4.26 that correlation between grain yield and physiological traits was positively significant for all characters in pooled data except between yield and crop growth rate which was negative and non-significant and between yield and growth duration which was though positive but non-significant. 
		The different agro-physiological traits like 1000-grain weight (r=0.9304), partitioning to spike at anthesis (r=0.8948), biological yield (r=0.8922),  number  of  grains  per spike (r=0.8351), number of tillers per 

Table 4.26 Correlation among yield and physiological traits in wheat under different dates of sowing
Sr. No.	Characters	1	2	3	4	5	6	7	8	9	10	11	12	13	
1	No. of Tillers m-2	1.0000	0.3209**	-0.0912	0.3216**	0.3962**	-0.2151	0.7907**	0.9239**	0.8341**	0.6014**	0.9051**	0.8351**	0.8323**	
2.	Leaf Area Index		1.0000	-0.5931**	0.6340**	0.5117**	0.6942**	0.5512**	0.2856*	0.3857**	0.4026**	0.4670**	0.5830**	0.6476**	
3.	Crop growth rate			1.0000	-0.0893	-0.0918	-0.3638**	-0.0827	0.0737	-0.0814	-0.0046	-0.0556	-0.1385	-0.2096	
4.	Pre-anthesis dry matter production				1.0000	0.4139**	0.3708**	0.5968**	0.3026**	0.4076**	0.5561**	0.5378**	0.6342**	0.6229**	
5.	Spike weight at anthesis stage					1.0000	0.2477*	0.4622**	0.4135**	0.3538**	0.2772*	0.4667**	0.3876**	0.4174**	
6.	Grain growth duration						1.0000	0.1998	-0.1698	0.0440	0.0483	-0.0599	0.1336	0.2103	
7.	Partitioning to spike at anthesis stage							1.0000	0.7516**	0.8661**	0.7272**	0.8927**	0.9044**	0.8948**	
8.	No. of spike m-2								1.0000	0.7413**	0.5187**	0.8298**	0.7497**	0.7822**	
9.	No. of grains/spike									1.0000	0.7086*	0.8952**	0.9006**	0.8351**	
10	Grain-spike weight ratio										1.0000	0.7411**	0.7731**	0.7090**	
11.	Biological  yield (q/ha)											1.0000	0.9291**	0.8922**	
12.	1000-grain weight (gm)												1.0000	0.9304**	
13.	Grain yield (q/ha)														
														1.0000	
* Significant at 5%
** Significant at 1%
Pooled data for five wheat varieties under five dates of sowing.

square metre (r=0.8323), number of spike per square metre (r=0.7822), grain-spike weight ratio (r=0.7090), leaf area index (r=0.6476) and pre-anthesis dry matter production (r=0.6229) showed highly significant correlation with grain yield.  So, they emerged as important attributes influencing grain yield in wheat.  These traits can be used as an index for screening thermotolerance in wheat.  These results are in accordance with the results given by Kumar et al (2001) and Pratik Satya et al (2002).
4.4	BIOCHEMICAL ANALYSIS
4.4.1	Chlorophyll Content (Milky Ripe Stage)

		The data given in Table 4.27 showed that the total chlorophyll and chlorophyll a were maximum in 7th Nov. sowing. The total chlorophyll increased from 15th Nov. to 6th Dec. in PBW-343 and PBW-509 varieties.  The total chlorophyll was found to be maximum in variety PBW-343 (0.967 mg g-1 FW) followed by PBW-509 (0.924 mg g-1 FW), Raj-3765 (0.912 mg g-1 FW), WH-542 (0.894 mg g-1 FW) and PBW-502 (0.769 mg g-1 FW) varieties.  
		The chlorophyll a was maximum in variety PBW-509 (0.655 mg g-1 FW) followed by Raj-3765 (0.612 mg g-1 FW) and PBW-343 (0.609 mg g-1 FW) varieties.  The rate of decline in total chlorophyll content of 7th Nov.  as  compared  to  6th  Dec.  sowing  was  3.5% in PBW-502, 1.4% in PBW-343, 18.9% in WH-542, 25.2% in PBW-509 and 20.5% in Raj-3765 varieties.   The  rate of decline was minimum in variety PBW-343 followed

Table 4.27 	Chlorophyll content (mg g-1 FW) in central spikelet husk at milky ripe stage in wheat varieties under different dates of sowing

Dates of sowing	PBW-502 		PBW-343 		WH-542 		PBW-509 		Raj-3765 	
	Chl.a	Chl.b	Total Chl.	Chl.a	Chl.b	Total Chl.	Chl.a	Chl.b	Total Chl.	Chl.a	Chl.b	Total Chl.	Chl.a	Chl.b	Total Chl.	
7th Nov. 	0.556	0.204	0.769	0.609	0.349	0.967	0.583	0.302	0.894	0.655	0.259	0.924	0.612	0.290	0.912	
15th Nov. 	0.466	0.252	0.725	0.457	0.143	0.505	0.404	0.160	0.571	0.426	0.196	0.628	0.406	0.186	0.598	
22nd Nov. 	0.504	0.209	0.712	0.549	0.321	0.879	0.481	0.218	0.707	0.407	0.220	0.634	0.551	0.277	0.836	
29th Nov. 	0.516	0.211	0.733	0.565	0.339	0.913	0.452	0.235	0.699	0.410	0.248	0.664	0.520	0.238	0.766	
6th Dec.  	0.523	0.201	0.742	0.577	0.368	0.953	0.482	0.240	0.725	0.425	0.241	0.691	0.482	0.235	0.725	

by PBW-502, WH-542, Raj-3765 and PBW-509 varieties.  So, PBW-343 emerged as a thermotolerant variety. Similar results were reported by Shubhra et al  (2006).
4.4.2	Quality Analysis of Grains
		Grain quality analysis are discussed as under: 
4.4.2.1	Total starch – Amylose and Amylopectin 
4.4.2.2	Total Protein – Gluten.
4.4.2.1   Total Starch
		The total starch and amylopectin content decreased significantly with delay in sowing whereas amylose content increased with delay in sowing. The normal (7th Nov.) and late (6th Dec.) sowing showed significant differences. Similar results were reported by Matsuki et al (2003).  The ratio of amylose to amylopectin (0.33 under 7th Nov., 0.34 under 15th Nov., 0.37 under 22nd Nov., 0.40 under 29th Nov. and 0.42 under 6th Dec.) was increased with delay in sowing.  Similar results were reported by Zhao-Hui et al (2006).
		The total starch content and its fractions amylose and amylopectin in wheat grain of five varieties under five dates of sowing are given in Table 4.28. The variety PBW-343 has maximum total starch (65.38%) and amylopection content (48.07%) whereas maximum amylose content was found in Raj-3765 variety i.e. (17.82%).

Table 4.28	The total starch content and its fractions amylose and amylopectin in different wheat varieties under different dates of sowing (% weight basis). 

Variety 	Total Starch 	
	7th Nov. 	15th Nov. 	22nd Nov. 	29th Nov. 	6th Dec. 	Mean	
PBW-502 	63.76	64.01	62.34	61.84	60.66	62.52	
PBW-343	67.45	66.98	66.72	63.51	62.27	65.38	
WH-542 	67.79	67.07	65.12	63.52	62.54	65.21	
PBW-509 	66.74	66.20	63.34	60.85	61.38	63.70	
Raj-3765 	64.24	63.58	62.90	61.00	60.20	62.38	
Mean	65.99	65.57	64.09	62.14	61.41		
CD (P = 0.05)   Dates (D) = 0.012	       Varieties (V) =  0.011 	 D x V =  0.025
Variety 	Amylose content 	
PBW-502 	15.77	16.03	16.86	17.27	17.93	16.77	
PBW-343	16.28	16.35	17.71	17.77	18.47	17.32	
WH-542 	16.44	16.22	17.25	17.93	18.39	17.25	
PBW-509 	16.48	16.64	17.26	17.70	18.29	17.27	
Raj-3765 	17.65	17.42	17.78	17.98	18.27	17.82	
Mean	16.52	16.53	17.37	17.73	18.27		
CD (P = 0.05)   Dates (D) = 0.033	       Varieties (V) =  0.011 	 D x V =  0.026
Variety 	Amylopectin content 	
PBW-502 	47.99	47.97	45.48	44.57	42.72	45.75	
PBW-343	51.16	50.62	49.01	45.74	43.80	48.07	
WH-542 	51.35	50.85	47.87	45.59	44.15	47.96	
PBW-509 	50.26	49.55	46.09	43.15	43.09	46.43	
Raj-3765 	46.59	46.15	45.12	43.03	41.94	44.57	
Mean	49.47	49.03	46.71	44.41	43.14		
CD (P = 0.05)  Dates (D) = 0.015	       Varieties (V) =  0.014 	 D x V =  0.032
		Pande et al (1998) showed that the tolerant variety had low amylose and high amylopectin content as compared to susceptible variety. Because tolerant variety increase the proportion of carbon preferentially in the form of more branched component i.e. amylopection under heat stress. So, variety PBW-343 exhibit high temperature tolerance characteristics. All the varieties showed significant differences in their total starch content. The dates of sowing and varieties interaction also showed significant differences. 
4.4.2.2  Total Protein
		Protein content is one of the important factor which determines the end-use of flour.  Gluten is a gum-like material which makes up about 80% of the protein in wheat. The protein and gluten content increased with delay in sowing. The percentage increase in total protein, dry gluten and wet gluten with delay in sowing from 7th Nov. to 6th Dec. was 11.31%, 8.41% and 9.23% respectively.
		The variety PBW-343 has maximum total protein and wet and dry gluten content. All the varieties differed significantly in their protein content. The protein content and yield components are negatively correlated.  The grain yield decreases whereas protein content increases with increase in temperature.  Similar results were reported by Rao et al (1993) and Blumental et al (1995). The interaction between varieties and dates of sowing differed significantly.  The grain protein content and gluten on wet and dry percentage basis of different wheat varieties under five dates of sowing are enlisted in Table 4.29.
Table 4.29	The total protein content and its major fraction gluten on wet and dry basis of wheat varieties under different dates of sowing.

Variety 	Protein (% weight basis) 	
	7th Nov. 	15th Nov. 	22nd Nov. 	29th Nov. 	6th Dec. 	Mean	
PBW-502 	10.56	10.68	10.87	11.64	12.08	11.16	
PBW-343	12.44	12.48	13.24	13.48	13.58	13.04	
WH-542 	12.06	12.75	13.07	13.21	13.30	12.88	
PBW-509 	10.48	11.62	12.14	12.49	12.96	11.94	
Raj-3765 	12.52	12.63	12.96	13.30	13.56	12.99	
Mean	11.61	12.03	12.46	12.82	13.09		
CD (P = 0.05)   Dates (D) = 0.028	       Varieties (V) =  0.011 	 D x V =  0.024
Variety 	Dry gluten (% weight basis)  	
PBW-502 	6.87	7.13	7.27	7.40	7.77	7.29	
PBW-343	7.37	7.70	7.77	7.80	7.87	7.70	
WH-542 	7.47	7.53	7.63	7.80	7.97	7.68	
PBW-509 	7.13	7.23	7.37	7.53	7.67	7.39	
Raj-3765 	7.10	7.37	7.67	7.90	8.00	7.61	
Mean	7.19	7.39	7.54	7.69	7.85		
CD (P = 0.05) Dates (D) = 0.089	       Varieties (V) =  0.042 	 D x V =  0.093
Variety 	Wet gluten (% weight basis)	
PBW-502 	24.23	24.87	25.40	26.60	27.53	25.73	
PBW-343	28.67	28.87	29.37	31.60	31.90	30.08	
WH-542 	28.73	29.07	29.37	30.73	31.40	29.86	
PBW-509 	25.33	26.13	26.33	26.40	27.30	26.30	
Raj-3765 	26.33	27.50	27.77	28.30	28.70	27.72	
Mean	26.66	27.29	27.65	28.73	29.37		
CD (P = 0.05)    Dates (D) = 0.16	       Varieties (V) =  0.10 	 D x V =  0.25
		The results illustrate that (i) Growing-degree days (GDD) accumulated more during reproductive stages than those from vegetative stages, which showed that rising temperature after anthesis play an important role in grain filling and crop maturity.  (ii) The important agro-physiological traits like number of effective tillers, leaf area index, pre-anthesis dry matter production, partitioning to spike at anthesis stage, number of spike m-2 grain growth duration, number of grains per spike, 1000-grain weight and thermal use efficiency (GDD accumulated) can be used as am index for screening thermotolerance in wheat varieties. (iii) The regression model showed a significant positive correlation between grain yield and GDD accumulated during watery ripe, hard dough, anthesis, physiological maturity, crown root initiation and milky ripe stages.             (iv) The correlation and path coefficient analysis showed that the physiological traits i.e. 1000-grain weight, partitioning to spike at anthesis, biological yield, number of grains per spike and number of effective tillers m-2 had highly  significant positive correlation with grain yield.  (v) The total chlorophyll content in central spikelet husk at milky ripe stage increased from 15th Nov.  to 6th Dec sowing in cvs. PBW-343 and PBW-509 and can be used as a reliable trait for screening thermotolerance in wheat. (vi) The amylose-amylopectin ratio increased with delay in sowing and can be correlated with the superior end-use quality of wheat grains. 

Chapter-V
Summary

		Wheat is the most important crop for the food security of ever increasing population of the world. High temperature during grain development is the most important factor that limits productivity of wheat in India. The extent and magnitude of growth and yield reduction in wheat largely depend on their adaptability to changed climate. Some physiological, morphological and quality traits can be used for screening wheat varieties under high temperature. 
		Field and laboratory experiment were conducted during rabi season 2006-2007 to find out the suitable agro-physiological traits associated with screening thermotolerance in wheat varieties and to understand the relationship between variation in grain yield and quality parameters under different environment.  
Results obtained from the experiments are summarized below:  
•	Growth duration (days) for the completion of entire growth period decreased in all varieties with delay in sowing from 7th Nov. to 6th Dec. The maximum growth duration (162, 156, 153, 149 and 142 days) was found in wheat variety PBW-343 under 7th Nov., 15th Nov., 22nd Nov., 29th Nov. and 6th Dec. sowing respectively followed by WH-542, PBW-502, PBW-509 and Raj-3765 varieties. 
•	The wheat variety PBW-343 accumulated maximum GDD units i.e. 1918.2, 1821.9, 1818.3, 1817.5 and 1745.2 under 7th Nov., 15th Nov., 22nd Nov., 29th Nov. and 6th Dec. sowing respectively followed by WH-542 variety. The percentage decline in GDD units for physiological maturity under 7th Nov. (normal) and 6th Dec. (late) sowing are 10.35, 9.02, 6.38, 11.73 and 10.49 for PBW-502, PBW-343, WH-542, PBW-509 and Raj-3765 varieties respectively. 
•	The physiological traits like Emergence count, Leaf are index, Pre-anthesis dry matter production (%), Spike weight at anthesis stage, Partitioning to spike, Grain growth duration (days) were maximum under 7th Nov. sowing and decreased with delay in sowing up to 6th Dec. 
•	The highest average rate of grain filling was 1.87 mg / grain /day under 6th Dec. sowing (late) and lowest (1.37 mg/grain/day) in 7th Nov. sowing (normal). Grain filling rate increased with delay in sowing. Crop growth rate also increased with delay in sowing.
•	The grain yield contributing traits like Number of spikes m-2, Number of grains per spike, Grain-spike weight ratio, 1000 grain weight (gm), Partitioning to spikes at anthesis stage, Biological yield (q/ha) decreases with delay in sowing from 7th Nov. to 6th Dec. sowing. 
•	The regression equation showed a significant positive correlation between grain yield and growth duration during hard dough (r=0.903), physiological maturity (r=0.895), watery ripe (r=0.834), soft dough (r=0.810) and milky ripe (r=0.799) stages. 
•	The regression equation between grain yield and GDD units accumulated during different phenophases also showed a significant positive correlation between grain yield and GDD accumulated during watery ripe (r=0.854), hard dough (r=0.849) anthesis stage (r=0.833), during the entire growth period (r=0.815) and crown root initiation (r=0.738).
•	The correlation and path coefficient analysis of different agro-physiological traits like 1000 grain weight (r=0.9304), partitioning to spike at anthesis (r=0.8948), biological yield (r=0.8922), number of grains per spike (r=0.8351), number of tillers (r=0.8323) showed highly significant positive correlation with grain yield. 
•	The grain yield was found maximum (51.40q/ha) in PBW-343 variety under 7th Nov. sowing followed by WH-542 (47.62q/ha) variety and decreases with delay in sowing up to 6th Dec. in all the varieties.
•	The total chlorophyll content was found to be maximum in variety PBW-343 (0.967 mg g-1 FW) under 7th Nov. (normal) sowing followed by PBW-509 (0.924), Raj-3765 (0.912), WH-542 (0.894) and PBW-502 (0.769) varieties. 
•	The quality analysis of grains revealed that the total protein content and its major fraction gluten increased with delay in sowing. The total starch, amylopectin decreases but amylose content increased with delay in sowing in all varieties. 
                         	Therefore, these results suggest that growing degree-days (GDD) is a best index for predicting the various phenological stages of wheat. The GDD accumulated more during reproductive stage than those from vegetative stages in all the varieties. The agro-physiological traits like leaf area index, pre-anthesis dry matter production, spike weight at anthesis, number of spikes per square metre, partitioning to spike at anthesis stage, number of grains per spike, grain-spike weight ratio, 1000-grain weight can be used for screening thermotolerance in wheat varieties under field conditions. The variety PBW-343 gave maximum grain yield due to its higher dry matter partitioning to spike at anthesis stage, higher crop growth rate after anthesis, more number of spike per square metre, higher test weight, higher chlorophyll content at milky stage and higher thermal use efficiency (GDD). The reduction in grain yield from post-heat stress is associated with reduction in kernel growth and poor carbohydrate supply to developing grain under late sown conditions. 

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ABBREVIATIONS 

CGR	:	Crop growth rate 	
Chl.	:	Chlorophyll 	
cm	:	Centimetre(s)	
cvs.	:	cultivars 	
DAA	:	Days after anthesis 	
DAS	:	Days after sowing 	
DOS	:	Dates of sowing 	
FW	:	Fresh weight 	
g	:	gram(s) 	
GDD	:	Growing degree days 	
GFD	:	Grain filling duration 	
GFR	:	Grain filling rate 	
GGR	:	Grain growth rate	
HI	:	Harvest index 	
LAI	:	Leaf area index 	
m-2	:	per square metre	
mg	:	milligram(s)	
r	:	Correlation coefficient 	

					VITA
Name of the student                       :  	 Amandeep Kaur                  		 
Father's name			:         	S. Amrik Singh 
Mother's name                		:        	Mrs. Lakhvir Kaur 
Nationality                      	:      	Indian 
Date of birth                   		:     	30th October, 1986
Permanent home address        	:      	Gurcharan Avenue,  
Nr. SDP School, 
M.K Road, Khanna 
Distt. Ludhiana 

EDUCATIONAL QUALIFICATION

Bachelor degree 	:	B.Sc. (Medical)

University and year of award	:	Panjab University, Chandigarh 				2006

% marks 	:	79.5

Master's degree 	:	M.Sc. (Botany)  

University and year of award 	:	Punjab Agricultural University, 				Ludhiana, 2008

OCPA	:	8.27/10.00

Title of Master's Thesis 	:	Screening of Agro-Physiological Traits for Thermotolerance in Wheat (Triticum aestivum L.)

Awards/Distinctions/	:	--
Fellowships/Scholarships