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Open Access
Biochemical and molecular studies on post-harvest physiological deterioration of cassava (Manihot esculenta crantz)
(Department of plant physiology, College of agriculture,Vellayani, 2015) Saravanan, R; KAU; Roy Stephen
The project entitled “Biochemical and molecular studies on post-harvest physiological deterioration of cassava (Manihot esculenta Crantz)” was conducted at the Dept of Plant Physiology, College of Agriculture, Vellayani and at ICAR-CTCRI, Thiruvananthapuram during 2013 to 2015. The main objective of the work was to analyse the physiological biochemical and molecular mechanisms associated with post harvest physiological deterioration (PPD) and develop methods to delay the PPD in cassava. The initial screening of the cassava genotypes for their performance of PPD was done with 61 different genotypes including some released varieties. Significant differences were observed for PPD development and shelf-life of harvested roots. Cassava genotypes such as IMS2-8, 9S-172, 11S-53, IRS 2-10 and 9S-286 started showing the visible discolouration in the parenchyma tissue earlier (less than 3 days of storage). Genotypes such as 9S-7, 9S-98, 11S-31, 11S-86, 11S-14, CE63-3, CI43-2, CR43-2, CR54-A5, CR59-8R, Sree Athulya and Kalpaka showed low PPD scores and better shelf-life. Tissue imprinting for peroxidase enzyme showed that there was a remarkable increase in peroxidase activity in the root tissues with increasing PPD symptoms. There was no correlation between the root morphological traits and PPD severity. Carotene and starch content of root did not influence the PPD in the genotypes studied. Chemotypic profile of roots with PPD symptoms was used to classify the genotypes based on PPD. To develop an objective screening tool, Near Infrared Spectroscopy (NIRS) was utilized to analyse root samples for PPD. Principal component analysis (PCA) and chemometric tools clearly grouped the different PPD category in root tissues. Various stains such as saffranin, aniline blue, erythrocin, fast green and phloroglucinol stained the tissue specifically at vascular tissues and other cell components and were not suitable for detecting PPD. Storage techniques such as storing the harvested roots in de-aerated bags, wax coating and burying the roots under the soil were employed with selected cassava varieties like Sree Athulya, Sree Jaya, Vellayani Hrashwa, Kalpaka and Sree Padmanabha to delay PPD. Wax coating was suitable to reduce PPD for few weeks. Effect of different storage temperature on PPD was studied for five cassava varieties. Root respiratory flux was higher in roots stored at ambient conditions compared to high (40o C) or low temperature (4o C) storage. There were significant positive correlation between root respiratory flux at 3 and 9 days of storage to the CAT and POX activities studied in different cassava varieties. Roots were treated with various food preservatives at two different concentrations (0.5 and 1%). There was a weak, but significant reduction in symptom development in butylated hydroxy touline – (BHT, at 0.5 and 1% level) treated roots compared to other treatments. Nearly three folds increase in total phenol content was noticed in BHT and butylated hydroxy anisole (BHA) treated roots. The plant hormones related to wound response such as Salicylic acid and jasmonic acid were used to study the PPD response in roots under storage. The roots did not show marked influence to hormone application. Significant genetic variation was observed for PPD. The low PPD type genotypes such as 9S-7, 9S-98, 11S-31, 11S-86, 11S-14, CE63-3, CI43-2, CR43-2, CR54-A5, Sree Athulya and Kalpaka can be utilized for breeding programmes. High temperature storage of cassava at 40 oC resulted in reduced respiratory rate and increased antioxidant scavenging enzyme activity and also reduced the PPD. Differentiation of cassava roots at the metabolites level corresponding to visual symptoms and chemotypic profile of PPD and NIR spectroscopy offer a rapid screening tools. Among the different storage treatments, wax coating with antiseptic pre-treatment is most suitable and economical for increasing shelf-life of roots. Food preservatives like BHT and BHA have a significant, albeit marginal influence on PPD symptom development in cassava.
Open Access
Photosynthetic efficiency and productivity of gynoecious parthenocarpic cucumber in naturally ventilated poly house
(Department of plant physiology, College of horticulture, Vellanikkara, 2015) Gayathri, Rajasekharan; KAU; Nandini, K
Poly house cultivation of vegetables is an emerging approach for production of vegetables in Kerala. The main principle of poly house cultivation is the facilitation of favourable micro-climates, which favour maximum production. The top of poly house is cladded with UV-stabilised plastic sheet which selectively screen the various spectral components of solar radiation and transform direct sunlight into scattered light inside. This type of spectral manipulation is aimed to specifically promote desired physiological processes and to modulate morphological and photosynthetic responses of plants. Hence, basic information on the physiological aspects involved in the photoresponse of crop in poly house is needed to realize maximum yield potential. In this context, a study was undertaken in a farmer’s field at Thannyam to compare the photosynthetic productivity of gynoecious parthenocarpic cucumber in poly house and open condition. High light intensity, Ultra violet (UV) radiation and Photosynthetically Active Radiation (PAR) caused a stressful environment which in turn reduced most of its morphological and biochemical characters in cucumber grown under open condition. However ambient CO2 concentration, which decides the photosynthetic rate was more under polyhouse condition. Poly house cladded with UV stabilized sheet, reduced light intensity, UV-radiation and PAR favoured most of the morphological characters of the crop. The morphological characters like leaf area, Leaf Area Index (LAI), number of leaves, number of nodes and internodal length were significantly high for poly house grown cucumber. The chlorophyll content- Chl a, b and total chlorophyll in leaves was significantly high when grown under poly house. However, the activity of IAA Oxidase (IAAO) observed at 15 and 60 DAS was significantly lower inside the poly house indicating auxin availability for morpho-physiological fuctions. The Gibberelic acid content also increased but significant difference was observed only at 75 DAS in poly house grown crop. Photosynthetic rate of the crop under both conditions when recorded gradually increased from 15 DAS to 45 DAS and thereafter declined. This was significantly high under open condition at 15, 30 and 45 DAS, whereas it was significantly high in poly house only at 60 and 75 DAS. The poly house crop could maintain higher photosynthetic rate even at later growth stages of crop thereby prolonging the crop duration. Transpiration rate was significantly high under open condition at 30 DAS, but significantly higher values were observed in poly house condition at 45 and 75 DAS. The lower photosynthetic rate was due to low influx of CO2 in to mesophyll cells which is evident from low intercellular CO2 concentration in the poly house crop. This is also related to high stomatal resistance inside the poly house at 15 and 30 DAS. The carboxylation efficiency, which relates to photosynthetic rate, was significantly high at 60 and 75 DAS in the poly house crop. The photochemical efficiency of PS II as indicated by Fv/Fm ratio was higher under poly house environment. Canopy temperature depression did not give any significant difference between two conditions. Light absorption coefficient was significantly high in open condition where the LAI was less. The lower values of light absorption coefficient observed inside the poly house may be related to high LAI. There was no significant difference in number of days to flowering and days to first harvest between open and poly house grown crops. But the number of days to last harvest and number of harvests made from poly house grown crop were significantly high when compared to open condition. The yield contributing components such as number of fruits per plant, fruit weight, yield per plant and marketable yield were significantly high for poly house grown crop. Early senescence of the crop was observed under open condition compared to poly house. Retention of more chlorophyll content even at later stages of crop delayed senescence in poly house grown crop. The ascorbic acid content, one of the quality parameter was significantly high in crop grown under open condition. Organoleptic evaluation of fruits revealed that the poly house grown crops maintained significantly high colour, texture and overall acceptability of the fruits. This study suggests that the diffused light and equal distribution of radiation over the crop canopy favoured morphological characters of poly house grown crop. This in turn helped the crop to maintain high photosynthetic rate and carboxylation efficiency even at later stages of the crop which resulted in increased number of harvest in poly house.
Open Access
Growth and physiology of isachne miliacea roth. in different soil types and its sensitivity to common herbicides
(Department of plant physiology, College of horticulture, Vellanikkara, 2015) Suada, A P; KAU; Girija, T
Isachne miliacea Roth. is one of the predominant weed in the low land rice fields of Kerala. The weed belongs to the family poaceae. Locally it is known as ‘Chovverippullu, Naringa, Njammal, Changalipullu.’ Previous studies conducted in Kerala Agricultural University showed that I. miliacea alone can contribute to 61 per cent reduction in the production of rice in Onattukara region. Presently, the weed is reported to be spreading to other rice growing regions of Kerala. It is found both during the Rabi and Kharif seasons. Eradication of the weed is very difficult, as it is propagated through seeds and stem cuttings. Hence a study was proposed to understand the growth and propagation of I. mliacea in different rice growing soils and also to understand the response of the weed to common herbicides popular in the state. The effect of different soil types on growth and phenology of I. miliacea was studied in pot culture with soil collected from five different rice growing regions viz. Onattukara, Kole, Kuttanad, Pokkali and Palakkad. Ten kg soil each was filled in plastic boxes of size 50 x 25 cm and five replications was maintained for each soil type. Ten seeds were sown in each box and the germination was noted. At two leaf stage when the seedlings were identifiable, a single seedling was retained in each box and the excess seedlings were removed, irrigated regularly and the different phenophases and the morphological attributes were observed at 15 days interval. The study showed that soil type had a profound influence on the phenology and growth pattern of the weed. Due to high acidity (pH -3.6) and salinity (EC – 4.46 dS/m) seeds sown in Pokkali soils did not germinate. Plants grown in Kuttanad soil showed earlier germination, tillering, flowering, seed formation and seed maturation, while those from Palakkad soil required more number of days to reach these phenophases. The variation in morphological attributes such as total shoot length, leaf number, internodal length, number of panicles and seeds produced per plant were significant. Plants grown in Palakkad soil had higher total shoot length and internodal length as compared to Kuttanad soil, but the leaf number, number of panicles per plant and number of seeds produced per panicle were higher in Kuttanad soil, where the potassium, phosphorus and organic content was higher compared to other soils. As the nutrient status of Onattukara and Kole land soils were similar (potassium, phosphorus, magnesium, zinc, manganese and sulphur), the performance of the weed in those two soil types were also on par for many of the morphological characters. Propagation of I. miliacea was affected by ambient temperature, shade, depth of burial and moisture level of soil. The seeds germinated when the temperature range was between 15 - 400C, the highest germination was obtained at 250C. Growth of the weed was highest in open condition compared to shaded condition. Under 50 per cent shade, seed germination declined by 70 per cent. Higher germination per cent of weed was obtained under moist condition, while stem cuttings performed well in both moist and submerged condition. The germination per cent of the weed, reduced with depth of burial. Sensitivity of the weed to pre emergence herbicides was tested using seed bioassay technique. In the first set, herbicide soaked filter paper was placed at the bottom of petri plates and seeds were placed on it (TP method). In the second set, the herbicide soaked filter paper was placed on top of the seeds and another water soaked filter paper was placed at the bottom (BP method I). In the third set, seeds were placed in between two filter paper soaked with herbicides (BP method II). BP method II gave the best result for all the pre emergence herbicides. However, oxyfluorfen and butachlor showed higher weed suppression in all the methods tried. Sensitivity of the weed to post emergence herbicides was tested using whole plant bioassay technique. Here, the weed was grown in mud pots and the herbicides were sprayed when the weed was in the vegetative phase. Among post emergence herbicides tested, best control was obtained for azimsulfuron followed by cyhalofop butyl and fenoxaprop p- ethyl. The weed was susceptible to these chemicals. In the case of bispyribac sodium and penoxsulam though initial control was observed, regrowth was seen after two weeks and so the chemical was classified as moderately resistant to the weed. The weed was resistant to pyrazosulfuron, where no drying symptoms were observed. All the four non-traditional rice herbicides tested viz., glyphosate, diuron, paraquat and glufosinate ammonium gave excellent control of I. miliacea and no regrowth was observed after two weeks
Open Access
Morpho-physiological changes in rice due to application of selected post emergent herbicides
(Department of Plant Physiology, College of Horticulture, Vellanikara, 2014) Ramanarayana, C V; KAU; Girija, T
The study on “Morpho-physiological changes in rice due to application of selected post emergent herbicides” was conducted during 2013-2014 at Alappad kole lands in farmer’s field. The objective of the experiment was to study the morphological, physiological and biochemical changes in rice due to application of Acetyl CoA carboxylase and Acetolactate synthase enzyme inhibitors and their effect on growth and yield of rice. The experiment was laid out in RBD with four replications and there were seven treatments comprising of three Acetyl CoA carboxylase enzyme inhibitors viz., Cyhalofop butyl, Fenoxaprop -p- ethyl and Metamifop and three Acetolactate synthase enzyme inhibitors viz., Bispyribac sodium, Azimsulfuron and Almix with Hand weeded as control. Herbicides were sprayed on 15 DAS. Observations on morphological, physiological, biochemical, yield attributes and yield of rice were recorded. Biochemical estimations were done on 7 days after herbicide application and at the time of flowering. Morphological characters were studied at 15 days interval. Herbicide application resulted in a two to four percent reduction in height and one to six percent reduction in tiller number of rice plant at harvest as compared to plants in the Hand weeded plot. Effect of herbicides on growth attributes viz., RGR, CGR and NAR indicated that at the initial and final stages of growth there was no significant difference between the treatments. However during the critical stages of growth i.e., 45-75 DAS significant variation was seen. Among the herbicide treatments, Bispyribac sodium.followed by Cyhalofob butyl applied plots had higher values as compared to the other herbicides. Azimsulfuron applied plots had the lowest value for these parameters. Among the growth indices LAI showed significant reduction irrespective of the herbicide throughout the growth stages as compared to Hand weeded control. The biochemical parameters such as nitrate reductase enzyme activity, phenol content, total soluble protein content and total amino acid content showed an initial decline when estimated one week after application of herbicide but by the time of flowering all the herbicide treated plants showed recovery. However the recovery was higher for Bispyribac sodium in the ALS inhibiting group and Cyhalofop in the ACCase inhibiting group. Proline content and catalase enzyme activity showed increase with herbicide application as compared to Hand weeded control indicating that application of these chemicals may be imparting stress to the plant, however by flowering time in most of the treatments there was recovery. Among the treatments, plants in the Almix and Azimsulfuron applied plots showed less recovery. The physiological parameters such as chlorophyll content, photosynthetic rate, stomatal conductance and IAA content showed decline when estimated one week after herbicide application. . In the case of chlorophyll content the recovery of the plant was comparatively less as compared to all other chemical constituents. Azimsufuron and Almix application contributed to maximum reduction in these constituents. Weed count and weed dry weight was taken on 60 DAS. The lowest values were recorded in Bispyribac sodium treatment. Azimsulfuron also a broad spectrum herbicide, was found less effective in the present study compared to Bispyribac sodium. In the present study, 5 to 17 percent reduction in grain yield and 6 to 17 percent reduction in straw yield of rice was observed by herbicide application. Among the ALS enzyme inhibitors, the lowest reduction in grain and straw yield was observed in Bispyribac sodium treatment and maximum reduction was in Azimsulfuron treatment. Among the ACCase enzyme inhibitors, Cyhalofop butyl showed least reduction in grain and straw yield of rice while fenoxaprop showed maximum reduction.
Open Access
Physiological, anatomical and molecular analysis of coconut palms (Cocos nucifera L.) affected with yellowing.
(Department of Plant Physiology,College of Agriculture, Vellayani, 2011) Deepa, S; KAU; Manju, R V
Kerala the ‘Land of coconut’ occupies first position in area and production of coconut in India but the productivity is below the national average. This is because of unproductive and senile palms, lack of adaptation of recommended cultivation practises and serious incidence of pests and diseases. The root (wilt), an endemic disease of Kerala causes an annual loss of 968 million nuts. Recently another type of yellowing characterised by mid whorl yellowing shedding of immature nuts and drying of inflorescence without showing characteristic ribbing symptom is rapidly spreading in many parts of Kerala. There is no research report available in this emerging problem in the coconut growing tracts of Kerala. Since there is rampant spreading of yellowing to other coconut cultivated areas causing a serious reduction in nut yield, this problem demands immediate attention. Hence an experiment was conducted in the Department of Plant Physiology, College of Agriculture, Vellyani to generate the basic information on the causative agents and on the changes of physiological, molecular and anatomical realms of coconut affected by mid whorl yellowing. A wide variation was observed in the physiological parameters like total pigments, relative water content, carbohydrate fractions, proteins, phenols and antioxidants betweenpalms with yellowing and control palms. The palms with yellowing showed a significant reduction in the total chlorophyll, chlorophyll a, chlorophyll b and carotenoid content when compared to the healthy palm. Relative water content was lower for all the palms with yellowing compared to the control palm and the healthy palms were maintaining a better water status and membrane integrity. All the selected palms with yellowing recorded an accumulation of reducing sugars compared to the healthy palms. The trend was similar for starch content except for palms with general yellowing. The control palms recorded maximum protein content compared to other palms with yellowing. A significant increase in the phenolic compounds was observed in palms with yellowing compared to the healthy palms. This results point to an activated defense system. The 14th leaf starting from the first fully opened one is the most widely used leaf for nutrient analysis as recommended by the IRHO. (Fremond et al., 1966).The 14th leaf data from the control palms and palms with different types of yellowing were analysed. The data showed that there were significant reductions in the levels of major nutrient nitrogen, phosphorus and also in the levels of magnesium and the micronutrient manganese in case of palms showing mid whorl yellowing compared to the control palm. But significantly higher levels of accumulation were found in case of potassium, calcium, iron and copper. These variations in the nutrient levels can have an influence on symptom development in coconut palms. The maximum yield was recorded for the control palm. Chlorophyll degradation and loss of structural integrity were evident from the anatomical studies of leaf tissues in case of palms with yellowing. Vascular browning which extended to the cortex and the vascular disintegration in the roots of affected palms were seen on anatomical analyses. A pure quality DNA was obtained by modified CTAB DNA isolation protocol. Molecular analyses using nested PCR showed that with the phytoplasma specific universal primers P1/P7-R16F2n/R16R2 provided an amplicon ) in the positive control and palms with inner and middle whorl yellowing and the primers R16mF2 /R16mR1 -R16F2n/ R16R2 provided an amplicon for the positive control and palms with inner, middle and general yellowing. The root (wilt) phytoplasma specific semi- nested primers IF7/7R3- IF7/7R2 provided an amplicon of 493 bp only for the positive control and no amplification was seen in any of the selected palms. The control palm and the palms affected with outer whorl yellowing provided no amplification at all for any of the primers tested. Amplification of phytoplasma specific universal primers in palms with mid whorl yellowing indicates that phytoplasma has got a role in development of the specific symptom. This demands immediate attention and extensive studies on the etiology, changes in biochemical profile, anatomy etc. Salient Findings Amplification of phytoplasma specific universal primers in palms with mid whorl yellowing indicates that phytoplasma has got a role in development of the mid whorl yellowing symptom. But in case of the root (wilt) phytoplasma specific primers, there was no amplification in palms with mid whorl yellowing. This suggests that the mid whorl yellowing of coconut palm which is an emerging problem in Kerala may not be associated with the root (wilt) disease. The results of biochemical and physiological analyses of the selected palms clearly indicate an altered primary metabolism, source-sink relation and a complexity in the nutriophysiology. These altered conditions can act as predisposing factors for the development of specific symptoms. The anatomical analyses showed damages of roots in the palms with mid whorl yellowing. They will have internal browning of vascular elements, extending into the cortex and also disintegration of vascular elements. Future line of work Detailed analysis of nutriophysiology, source-sink relation and hormonal profile. Studies on soil factors like nutrient level and water status. Extension of anatomical studies to different type of tissues. Extension of molecular studies into identification of specific phytoplasmal strains associated with mid whorl yellowing of coconut palms. Development of management strategy for the improvement of the field performance and productivity of coconut palms with mid whorl yellowing.
Open Access
Physiological, phytochemical and molecular studies on abiotic stress mediated antioxidant accumulation in Amaranthus spinosus Linn.
(Department of Plant Physiology, College of Agriculture, Vellayani, 2014) Garggi, G; KAU; Roy, Stephen
The study entitled “Physiological, phytochemical and molecular studies on abiotic stress mediated antioxidant accumulation in Amaranthus spinosus Linn.” was conducted during the period 2012-14 in the Department of Plant Physiology, College of Agriculture, Vellayani, Thiruvananthapuram. The objective of the study was to elicit information on the physiological, biochemical and molecular attributes associated to the antioxidant accumulation due to abiotic stress factors viz. light stress and water deficit stress and CO2 enrichment in Amaranthus spinosus Linn. The study was conducted as two separate experiments. One experiment was laid out in pot culture at Instructional Farm Vellayani, in Completely Random Design (CRD) with nine treatments which included combinations of three levels of water deficit stress and three levels of shade stress in three replications. The second experiment was laid out in Open Top Chamber (OTC) in CRD with six treatments which included combinations of CO2 enrichment and two levels of water deficit stress in four replications. The observations on growth parameters revealed a general increase in plant height under shaded condition. Leaf area was maximum for plants under 50% FC and 25% shade, T6 (42.663 cm2) and plants under 50% FC and 50% shade, T3 (40.567 cm2). The results of physiological observation showed maximum concentration for total chlorophyll for plants under 50% FC and 25% shade, T6 (1.947 mg/g of leaf tissue). The analysis of biochemical parameters showed the plants under 25% shade + 100% FC (T4) and plants under open condition + 50% FC (T9) had maximum starch content of 8.963 mg/g and 8.49 mg/g respectively. The results of enzymatic antioxidant assays showed Superoxide dismutase activity was higher for plants under treatments T9 (Open + 50% FC) and T3 (50% shade + 50% FC); 0.032 Units. The non-enzymatic antioxidant assays showed the maximum Ascorbic acid content of 3.6mg/g for treatment T1 (50% shade +100% FC) and Vitamin A content was maximum for T3 (50% shade +50% FC). Total flavonoids recorded highest in plant under treatment T2 (50% shade+75 % FC) whereas total phenol was maximum for the treatment T7 (Open + 100% FC).CO2 enrichment has no significant effect on plant height. Stomatal conductivity was significantly low for CO2 enriched plant under 100% FC (25.35 m moles s-1 for OT1) and 50% FC (21.8 m moles s-1 for OT2). Plants under CO2 enrichment and 50% FC showed maximum Catalase activity (0.169 Units).CO2 treatment did not show a significant variation with respect to antioxidants. Expression level study of the gene CHS (Chalcone synthase) revealed overexpression of the gene under abiotic stress, especially under moderate shade stress. Hence the plant can be exploited for its therapeutic value and can be cultivated as an intercrop in plantations.
Open Access
Effect of UV-B radiation on physiological and phenological plasticity in rice (Oryza sativa L.)
(College of Horticulture, Vellanikkara, 2015) Wagh, Yogesh Sahebrao; KAU; Nandini, K
A global depletion of the stratospheric ozone layer, largely due to the release of pollutant such as chlorofluorocarbons (CFCs) caused by human activities, has resulted in an increase of solar Ultraviolet-B (UV-B) radiation in the range of 280-320 nm at the earth’s surface. Elevated UV-B exposure causes temporary or irreversible damage to plant growth and development. Though UV-B is only a minor component of total solar radiation (less than 0.5%), due to its high energy, its potential for causing biological damage is very high. UV-B radiation is highest in tropical region where rice is grown as the major food crop in these regions. Decline in rice yield during puncha season (Dec-March) gives an indication on the effect of UV-B radiation on rice yield. Failure of rice crop in puncha season has lead to abandoning of double cropping in productive rice ecosystem like kole lands of Kerala. This needs detailed investigations to come up with realistic recommendations to overcome such situations. Therefore, the present study was conducted to understand the effect of UV-B radiation on morphological, physiological, phenological and biochemical changes in rice (Oryza sativa L.). The experiment was conducted in pot culture during December 2013-April 2014, with two varieties Jyothi and Uma under three different levels of UV-B radiation i.e. - natural solar UV-B condition where crops were exposed to 100% natural solar radiation (T1), reduced UV-B radiations using UV-B Mylar film which measures UV-B as zero (T2) and 85% ambient radiation including UV-B + UV-B supplemented with UV-B lamps in polyhouse (T3). The results indicated that UV-B radiation, in the range of 1.30 to 3.58 Wm2, during the study period affected the productivity of the crop. There was significant variation in UV-B radiation from 10 am to 4 pm in all the months throughout the growing period and the maximum value was recorded during the month of March, 2014. The highest crop yield was recorded in UV-B excluded condition (T2). This was due to more No. of spikelet per panicle, filled grain per panicle and 1000 grain weight. High photosynthetic rate, stomatal conductance and more canopy cooling at both vegetative and reproductive phases, along with more IAA content, total chlorophyll and chlorophyll ‘a’ have contributed the high yield in T2 condition. The increase in physiological parameters like photosynthetic rate, stomatal conductance and canopy cooling; morphological traits like flag leaf angle and panicle length and biochemical constituents like Chlorophyll ‘a’, total chlorophyll and IAA content observed under UV-B excluded condition (T2) positively favoured the high yield and harvest index in the present study. Though the crop grown under natural solar radiation expressed more No. of productive tillers per hill, it could not produce more No. of spikelet and filled grain per panicle. Instead it produced more amount of flavanoid and phenol content by channelizing the photo assimilates at flowering stage. The phenophases of the crop like days to heading, 50% flowering and days to harvestable maturity were delayed by 4-5 days under open condition (T1).The varieties Jyothi and Uma could not produce significant difference in yield. In the present study decrease in yield and yield attributes were observed due to the current level of natural solar UV-B radiation. The UV-B radiation under open condition restricted filling of grain and further grain development leading to lesser number of filled grains per panicle and thousand grain weight.
Open Access
Evaluation of selectively fertilized coconut hybrids (Cocos nucifera L.) for water use efficiency through stable isotope discrimination
(College of Agriculture, Vellayani, 2015) Aisha, Renju N A; KAU; Roy, Stephen
A study entitled “Evaluation of selectively fertilized coconut hybrids (Cocos nucifera L.) for water use efficiency through stable isotope discrimination” was undertaken with an objective to evaluate the selectively fertilized coconut hybrids for water use efficiency, and to study the mechanism of water stress tolerance in coconut, and to estimate genetic variability in coconut for water use efficiency through stable isotope discrimination. A pot culture experiment was conducted for three months in Rain out shelter of the Department of Plant Physiology, where one year old coconut seedlings of seven coconut varieties and hybrids (Kerasree, Keraganga, Malayan Yellow Dwarf, Gangabondam, West Coast Tall and selectively fertilized hybrids of Kerasree and Keraganga) were grown and evaluated for water use efficiency through gravimetric method. The experiment was laid out in CRD with equal sets of seedlings under two treatments viz 100 % Field Capacity (T1) and 50 % Field Capacity (T2) with 3 replications. Water transpired from individual seedlings were estimated daily through gravimetry. The transpiration loss was replenished by adding specific quantity of water to maintain the plants at respective soil moisture levels. Total dry matter accumulation was determined through the initial and final samplings. Physiological and biochemical analyses were done at monthly intervals. At the end of three months, leaf samples from experimental seedlings were collected and sent to Isotopic Ratio Mass Spectrophotometric (IRMS) facility, UAS Bangalore for stable isotope discrimination. Meanwhile, leaf samples from adult palms of 30 coconut genotypes were collected from RARS, Pilicode and sent for stable isotope discrimination. Among all genotypes, Kerasree S.F exhibited highest WUE (6.3 g/kg) under T2 by accumulating maximum dry matter (188.33 g) with a comparatively lower volume of cumulative transpired water. Results of carbon isotope discrimination was negatively correlated with gravimetric data of WUE so that genotype with highest water use efficiency (Kerasree S.F) marks the lowest discrimination value for C 13 (19.90). Decreased stomatal frequency and stomatal conductance up to 3 months in all coconut genotypes resulted in decreasing transpiration rate under 50 % F.C (T2). Relative water content was decreasing over the period of study under T2 for all varieties and highest tissue moisture content was maintained by Kerasree S.F (80.19 %). Wax deposition under water stress was highest in Kerasree (3.93 mg/cm2). Highest membrane integrity and chlorophyll stability index (99.19 %) under T2 was noticed in MYD. Pigment components viz chlorophyll a, chlorophyll b, total chlorophyll and carotenoids decreased with the extent of stress. Total soluble protein content decreased in all coconut types under T2. Proline content and activity of enzymatic antioxidants were high in selectively fertilized hybrid of Kerasree. Genetic variation for C13 discrimination was studied in 30 coconut genotypes that includes Talls, Dwarfs and Hybrids and the data revealed a discrimination range of (18.37-21.07). Among the coconut genotypes evaluated for WUE, hybrid Kerasree S.F was found to be the most water use efficient genotype under water deficit treatment, which coincides with its lowest value for C13 discrimination. Hence the study revealed that stable isotope discrimination can be used as an alternative for gravimetric method to screen out water use efficient genotypes. Moreover, efficacy of stress tolerance screening technique like selective fertilization is once again proved, which offers great prospects for drought tolerance breeding in perennials.
Open Access
Biochemical and molecular studies on post-harvest physiological deterioration of cassava (Manihot esculenta crantz)
(College of Agriculture, Vellayani, 2015) Saravanan, R; KAU; Roy, Stephen
The project entitled “Biochemical and molecular studies on post-harvest physiological deterioration of cassava (Manihot esculenta Crantz)” was conducted at the Dept of Plant Physiology, College of Agriculture, Vellayani and at ICAR-CTCRI, Thiruvananthapuram during 2013 to 2015. The main objective of the work was to analyse the physiological biochemical and molecular mechanisms associated with post harvest physiological deterioration (PPD) and develop methods to delay the PPD in cassava. The initial screening of the cassava genotypes for their performance of PPD was done with 61 different genotypes including some released varieties. Significant differences were observed for PPD development and shelf-life of harvested roots. Cassava genotypes such as IMS2-8, 9S-172, 11S-53, IRS 2-10 and 9S-286 started showing the visible discolouration in the parenchyma tissue earlier (less than 3 days of storage). Genotypes such as 9S-7, 9S-98, 11S-31, 11S-86, 11S-14, CE63-3, CI43-2, CR43-2, CR54-A5, CR59-8R, Sree Athulya and Kalpaka showed low PPD scores and better shelf-life. Tissue imprinting for peroxidase enzyme showed that there was a remarkable increase in peroxidase activity in the root tissues with increasing PPD symptoms. There was no correlation between the root morphological traits and PPD severity. Carotene and starch content of root did not influence the PPD in the genotypes studied. Chemotypic profile of roots with PPD symptoms was used to classify the genotypes based on PPD. To develop an objective screening tool, Near Infrared Spectroscopy (NIRS) was utilized to analyse root samples for PPD. Principal component analysis (PCA) and chemometric tools clearly grouped the different PPD category in root tissues. Various stains such as saffranin, aniline blue, erythrocin, fast green and phloroglucinol stained the tissue specifically at vascular tissues and other cell components and were not suitable for detecting PPD. Storage techniques such as storing the harvested roots in de-aerated bags, wax coating and burying the roots under the soil were employed with selected cassava varieties like Sree Athulya, Sree Jaya, Vellayani Hrashwa, Kalpaka and Sree Padmanabha to delay PPD. Wax coating was suitable to reduce PPD for few weeks. Effect of different storage temperature on PPD was studied for five cassava varieties. Root respiratory flux was higher in roots stored at ambient conditions compared to high (40o C) or low temperature (4o C) storage. There were significant positive correlation between root respiratory flux at 3 and 9 days of storage to the CAT and POX activities studied in different cassava varieties. Roots were treated with various food preservatives at two different concentrations (0.5 and 1%). There was a weak, but significant reduction in symptom development in butylated hydroxy touline – (BHT, at 0.5 and 1% level) treated roots compared to other treatments. Nearly three folds increase in total phenol content was noticed in BHT and butylated hydroxy anisole (BHA) treated roots. The plant hormones related to wound response such as Salicylic acid and jasmonic acid were used to study the PPD response in roots under storage. The roots did not show marked influence to hormone application. Significant genetic variation was observed for PPD. The low PPD type genotypes such as 9S-7, 9S-98, 11S-31, 11S-86, 11S-14, CE63-3, CI43-2, CR43-2, CR54-A5, Sree Athulya and Kalpaka can be utilized for breeding programmes. High temperature storage of cassava at 40 oC resulted in reduced respiratory rate and increased antioxidant scavenging enzyme activity and also reduced the PPD. Differentiation of cassava roots at the metabolites level corresponding to visual symptoms and chemotypic profile of PPD and NIR spectroscopy offer a rapid screening tools. Among the different storage treatments, wax coating with antiseptic pre-treatment is most suitable and economical for increasing shelf-life of roots. Food preservatives like BHT and BHA have a significant, albeit marginal influence on PPD symptom development in cassava.

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