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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
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.
Open Access
Marker assisted transfer of thermosensitive genic male sterility to high yielding red kernelled varieties of rice (Oryza sativa L.)
(College of Agriculture, Vellayani, 2015) Niya, Celine V J; KAU; Roy, Stephan
The project entitled “Marker assisted transfer of thermosensitive genic male sterility to high yielding red kernelled varieties of rice (Oryza sativa L.)” was conducted in the Department of Plant Physiology, College of Agriculture, Vellayani during 2011 to 2014. The main objectives were to develop molecular markers associated with TGMS gene and to transfer TGMS character to red rice background. For the present investigation, two TGMS lines were imported from International Rice Research Institute (IRRI) namely, TGMS1 and TGMS2which are from two different TGMS sources ID24 and IR32364 respectively. The TGMS lines along with two popular red rice varieties of Kerala, Uma and Jyothi were sown on monthly intervals for their initial phenological study. The critical sterility temperature and period of TGMS lines were characterised in the field using tracking method. The activity of antioxidant enzymes plays an important level in causing sterility in rice pollen grains, though the reason behind male sterility is unknown. Morphological, agronomic and floral traits were studied during the specific crop growth stage and were recorded as per the standard evaluation systems given by IRRI. Phenological, floral and morpho-agronomic characterisation of TGMS lines revealed that the line TGMS1 performed better with short stature, early maturity, more productive tillers, wider glume opening, higher panicle and stigma exertion, more filled grains and longer panicles. Stages of panicle development were determined by various methods viz., physical method, morphological index method and tracking method. The results have shown that TGMS1 is a better candidate for Kerala condition with critical sterility period of 15-22 days before heading and the sterility inducing average temperature of 27.25 o C. For hybridisation, TGMS1 plants were grown under sterility inducing condition and they were crossed with a popular red rice variety, Uma to produce F1. The F1 s were then selfed to get F2 population. A gene specific primer was designed for the red pericarp colour (Rc) which can be used as a background selection marker. Fifty F2 plants were used for marker analysis. Microsatellite analysis was done to find out the SSR markers polymorphic to the tms gene. DNA was isolated from the 50 F2 plants and performed PCR using 45 SSR markers. Capillary electrophoresis was done for the allele sizing of PCR products. Among 45 SSR markers used, three primers RM 3351, RM23 and RM31 could differentiate Uma, Jyothi andTGMS1, TGMS2. A set of twenty one primers were able to distinguish TGMS1 and Uma. The F2 plants sterile as per the TGMS markers were found to be sterile under sterility inducing condition. Under low temperature their fertility was transformed indicating the presence of tms gene. Linkage analysis using MAPMAKER version 3.0, seven linkage groups and a few unlinked primers were found. A segregation ratio of 2.57:1 was obtained between fertile and sterile lines. This ratio explains the monogenic nature of tms gene.Among 20 polymorphic markers, six (RM23, RM31, RM3351, RM 212, RM258 and RM244) were found significant. These on further analysis using χ 2-test revealed the possible association between the sterility phenotype and marker. From the present study, the sterility tms gene got successfully transferred into 14 sterile F2 plants and RM31, RM23, RM3351, RM212, RM244 and RM258 can be used for the evaluation of TGMS1 X Uma hybrids and their F2s.
Open Access
Physiological and molecular analyses of growth responses in black pepper (piper nigrum L.) under elevated carbon dioxide environments
(College of Agriculture, Vellayani, 2015) Minu, M; KAU; Manju, R V
A study entitled ‘Physiological and molecular analyses of growth responses in black pepper (Piper nigrum L.) under elevated carbon dioxide environments’ was carried out with the objective to study the physiological, molecular and biochemical basis of growth responses in black pepper (Piper nigrum L.) under elevated CO2 conditions. In this study, 8 month old rooted cuttings and bush pepper plants of 3 varieties viz. Panniyur 1, Panniyur 5 and Karimunda were used. Technologies used for CO2 enrichment were Open Top Chamber (OTC) and Trench Systems. CO2 was released from CO2 cylinders to one of the two OTCs bringing the CO2 level to 500ppm (OTC Ec) and the second OTC worked as a control at ambient CO2 for chamber effect (OTC Ac). In trench system, CO2 concentration was enhanced to a level of 480 ppm. The plants were maintained under high CO2 level for a period of two months in both the systems. The experiment was laid out in CRD with 4 treatments and 3 replications. Observations on growth parameters and molecular studies were conducted at the end of exposure period and physiological and biochemical parameters were taken at monthly intervals. Elevated CO2 was found to have a promotional effect on all the growth parameters compared to absolute control. An increase of 18% was noticed in plant height, 84% in leaf production, 174.4% in leaf area, 147.8% in net assimilation rate, 51.1% in relative growth rate, 87.5% in root weight, 25.3% in shoot weight, 42.1% in root-shoot ratio and 62.27% in dry matter production. Specific leaf areawas found to have a 13.3% reduction under elevated CO2. Under elevated CO2, the variety Panniyur 1 bush recorded highest net assimilation rate (0.066 mg cm-2 day -1), relative growth rate (0.0078 mg g-1 day-1), shoot weight (13.03 g) and dry matter production (10.07 g). Highest root production, root shoot ratio and lowest transpiration rate were noticed in Karimunda variety. CO2 enrichment significantly lowered the stomatal frequency (1311 No. cm-2), stomatal conductivity (28.70 mmoles m s-1) and transpiration rate (0.72 mmoles m-2 s-1) in all the varieties except for Panniyur 5 bush pepper resulting in better relative water content. Photosynthetic pigments in all varieties (chlorophyll a, chlorophyll b, total chlorophyll and carotenoids) were increased under elevated CO2. Elevated CO2 had significant positive influence on biochemical parameters like total soluble protein (6.40 mg g-1), starch (29.92 mg g-1), reducing sugars (15.06 mg g-1), phenol content (0.70 mg g-1), free amino acids (2.59 mg g-1) and wax concentration (2.65mg cm-2). Though there was a reduction in membrane integrity during the initial phase, it got stabilized at later stages. Isotope discrimination values were enhanced under elevated CO2 in all the varieties except Panniyur 5. CO2 enrichment was found to have significant influence on peroxidase (2.41 activity g-1 min-1) and superoxide dismutase (0.91 activity g-1 min-1) activities but in the case of catalase and ascorbic acid no significant variation was observed. Protein profile revealed that elevated CO2 induced the production of a few new proteins but suppressed certain others. The expression levels of both the large and small subunits of rubisco were slightly brought down by CO2 enrichment. The plants kept in trench system also responded in a similar manner but to a lesser extent. The present study revealed that elevated CO2 environment had a positive influence on growth and development of pepper. Panniyur 1 was the best performing bush pepper. Pepper plants of the variety Karimunda had the best root characters, high mesophyll efficiency and low transpiration rate under elevated CO2 environments which makes it suitable for water limited situations with higher water use efficiency.

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