1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)
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Item Drought mitigation in Okra (Abelmoschus esculentus L.) through chemical approach(Department of Plant Physiology, College of Agriculture, Padannakkad, 2021) Fathimath Suhaila; Sudarsana Rao, G VOkra or Bhindi (Abelmoschus esculentus L.) is one of the most popular summer vegetable crop grown widely in Kerala for its edible green fruits. Drought is a major yield limiting factor in agriculture and vegetables are more sensitive to drought stress as compared to most of the field crops because of their high water requirement. Hence, the study entitled “Drought mitigation in okra (Abelmoschus esculentus L.) through chemical approach” was carried out with the objective to investigate the influence of different chemicals namely, salicylic acid, ascorbic acid and thiourea on mitigation of drought and to evaluate their effect on morphological, physiological and yield charcteristics of okra. The field experiment was laid out in randomized block design with 8 treatments and 3 replications at RARS, Pilicode during December 2019 to March 2020. The okra variety Arka Anamika was raised as per standard package of practices recommendations of Kerala Agricultural University and also under soil test based nutrient management system. The experiment consisted of 8 treatments viz., normal irrigation (T 1 ) as control, drought stress (T 2 ), T 2 + salicylic acid foliar spray @ 1 mM (T 3 ), T 2 + salicylic acid foliar spray @ 2 mM (T 4 ), T 2 + ascorbic acid foliar spray @ 1 mM (T 4 ), T 2 + ascorbic acid foliar spray @ 2 mM (T 5 ), T 2 + thiourea foliar spray @ 500 ppm (T7), T 2 + thiourea foliar spray @ 1000 ppm (T8). Foliar application of chemicals were given at 10, 20 and 30 DAS and stress was induced by withholding irrigation from 25 days of sowing and re-irrigation was given at 50 per cent field capacity. Morphological, physiological and biochemical parameters were recorded at 25, 50 and 75 DAS and the yield and fruit quality characters were recorded at the time of harvest. A perusal of morphological data showed that T 3 had maximum plant height, number of leaves plant -1 , number of pickings and highest duration of the crop followedby T 6 when compared to all other treatments. The maximum number of branches per plant and the highest root volume were recorded in T 1 which was on par with T 3 followed by T 6 . Foliar spray of chemicals did not significantly influence number of days for 50 per cent flowering and first harvest. Up to 75 DAS, maximum relative growth rate was observed T 3 . All the treatments performed better than drought stress treated crops. At all the growth stages, maximum specific leaf weight was exhibited T 3 . Leaf area was observed maximum for T 3 and was on par with T 4 , T 5 , T 6 at 25 DAS and T 1 , T 4 and T 6 at 50 DAS and T 6 at 75 DAS. The relative leaf water content was recorded the highest for T 3 at 25 DAS and for T 1 at 50 and 75 DAS. At 50 DAS, T 1 was on par with T 3 , T 6 and T 7 and at 75 DAS T 1 was followed by T 3 and T 6 . T 3 had maximum total dry matter production which was on par with T 1 and T 4 .at 25 and 50 DAS, respectively. Root shoot ratio was recorded maximum in T 3 which was on par with T 1 at 25 and 50 DAS. SPAD chlorophyll meter reading (SCMR) was recorded maximum in T 3 at 25 and 50 DAS and in T 1 at 75 DAS. T 1 was on par with T 3 , T 4 and T 6 at 75 DAS. Considering the yield and fruit quality attributes, T 4 recorded maximum value for fruit length and was on par with T 1 , T 7 and T 8 . The highest average fruit girth and fruit weight were exhibited in T 3 and lowest was in drought stressed crop (T 2 ). The treatment T 1 , T 3 , T 4 and T 6 recorded maximum number of fruits plant -1 which were on par with T 5 and T 7 . The highest total fruit yield was recorded in foliar spray of salicylic acid (1 mM) followed by ascorbic acid (2 mM). These treatments recorded 45 per cent and 41 per cent higher yield over drought stressed treatment, respectively. The crude fibre content was recorded highest for drought stressed crops (T 1 ) and the lowest was recorded in T 3 . The ascorbic acid content was observed maximum in T 1 followed by T 5 and T 6 . The highest net returns and BCR was obtained in T 3 followed by T 6 . The frequency of irrigation given was highest in T 1 followed by T 2 and T 8 . The lowest frequency of irrigation given were in T 3 , T 6 and T 7 . The irrigation interval was more with T 3 , T 6 and T 7 (5 days).It can be concluded that morphological, physiological, biochemical and yield traits of okra were severely affected under drought stress. Among the three drought mitigating chemicals, salicylic acid (1 mM) recorded maximum values for morphological traits viz., plant height, number of leaves plant -1 , root volume and duration of crop, followed by ascorbic acid (2 mM), which also significantly improved morphological traits of okra compared to all other treatments. Physiological traits such as total dry matter production, leaf area plant -1 , relative growth rate, specific leaf weight, root shoot ratio and SPAD chlorophyll meter reading increased over drought stress crop when sprayed with salicylic acid (1 mM) and ascorbic acid (2 mM). Salicylic acid (1 mM) and ascorbic acid (2 mM) is beneficial for getting higher fruit yield and maximum economic returns over drought stressed and normal irrigated crops. Therefore, application of salicylic acid (1 mM) and ascorbic acid (2 mM) significantly mitigated the harmful effect of drought stress in okra.Item Identification of microsatellite markers associated with root traits for drought tolerance in rice (Oryza sativa L.)(Department of Plant Technology, College of Agriculture, Vellayani, 2017) Rejeth, R; Beena, RItem Assesment of multiple abiotic stress tolerance mechanisms in rice (Oryza sativa L.)(Department of Plant Biotechnology, College of Agriculture,Vellayani, 2019) Alif Ali, B S; Beena, RThe study entitled “Assessment of multiple abiotic stress tolerance mechanisms in rice (Oryza sativa L.)” undertaken at the Department of Plant Physiology, College of Agriculture, Vellayani during 2018-19. The objective was to study the multiple abiotic viz. drought, salinity and high temperature stress tolerance mechanisms in rice and to validate the identified QTLs for stress tolerance in rice. The investigation comprises four experiments, In experiment I initial screening of 20 rice genotypes for single abiotic stress tolerance was studied. Stresses were induced using different concentrations of PEG6000, NaCl and temperature controlled incubator for providing drought, salinity and temperature stresses respectively. Germination study was carried out using paper towel method. In the first experiment drought stress were given at concentrations -1bar, -3bar, 5bar and -7bar water potentials of PEG6000, salinity stress was given at 100mM, 150mM, 200mM, 250mM NaCl and temperature stress were given at 350C, 400C, 450C and 500C for all 20 rice varieties with two replications. The physio-morphological and biochemical parameters were studied on 14th day of germination. The highest level drought, salinity and temperature stresses at which germination occurred was selected as Dh (-5 bar), Sh (250mM NaCl) and temperature (Th) (350C) respectively. Among 20 rice varieties, PTB-7, PTB-60 and PTB-35 showed maximum seedling vigour at highest level of drought stress (Dh) stress condition Vyttila-9, MO-18 and Vyttila-3 recorded maximum seedling vigour index at highest tolerated level of salinity (Sh) stress condition and N-22, NL-44 and Vyttila -6 showed maximum seedling vigour index at highest tolerated level of temperature stress (Th) stress condition. These nine genotypes were selected for the evaluation of combination stress treatment In the second experiment, The combination stress treatments given were Dh x Sh, Dh x Th, Th x Sh and Dh x Sh x Th. Rice varieties did not germinated at Dh x Sh and Dh x Th. The maximum seedling vigour index at Dh x Sh and combination stress treatment was observed in PTB-7, Vyttila-9, PTB-35 and at Th x Sh was observed in NL-44, MO-18 and N-22 respectively. These rice varieties were selected as tolerant varieties. In experiment III six rice varieties selected from combination stress treatment were evaluated for yield parameters in pot culture experiment. The design of the experiment was CRD with two replications and one control. Drought and salt stress were imposed during reproductive stage for 5 days by applying -5bar PEG6000 and 250mM NaCl solutions respectively into the pots containing rice varieties, Temperature stress was induced using a temperature controlled polyhouse from panicle initiation to maturity stage. Physio-morphological, biochemical and yield parameters were studied under the combination stress treatments. Highest yield under the combination stress treatment of Dh x Sh was observed in PTB-7 and highest yield under the combination stress treatment Th x Sh was observed in N-22. Based on morpho-physiological and yield parameters PTB-7 was selected as the tolerant variety under drought and saline condition and N-22 was selected as the tolerant variety under temperature and salinity condition. In experiment IV all the 20 genotypes were analyzed for the identification of reported markers linked to stress tolerance such as drought salinity and temperature. Reported microsatellite markers linked to drought, salinity and temperature were used to screen 20 rice varieties. Among the markers distinct polymorphism for temperature tolerance between temperature tolerant (N-22 and NL-44) and susceptible varieties was shown by RM 6100. RM 7076 showed distinct polymorphism in tolerant varieties PTB-7 and NL-44 . RM 1287 showed distinct polymorphism for salinity tolerance in PTB-7 and N-22. Drought tolerance between drought tolerant (PTB-7) and susceptible varieties was Shown by RM 490.Item Silicon nutrition for rice in iron toxic laterite soils of Kollam district(Department of Agronomy, College of Agriculture, Vellayani, 2017) Guntamukkala Babu Rao; Poornima Yadav, P IItem Oxidative stress and protein profiling in cassava (Manihot esculenta Crantz) under abiotic stresses(Department of Plant Biotechnology, College of Agriculture, Vellayani, 2015) Sreekuttan, K S; Ravi, VThe present study an “Oxidative stress and protein profiling in cassava (Manihot esculenta CRANTZ) under abiotic stresses” was conducted during the period 2014- 2015 in the Division of Crop Production, CTCRI (Central Tuber Crop Research Institute) Thiruvananthapuram. The objective of the study was to elict information on the antioxidative enzyme activity, protein profiling, growth parameter and yield parameter of four varieties / genotypes of cassava under irrigated, high temperatures stress (40 o C ±2 o C) and water deficit stress (WDS) conditions and identify marker physiological parameter which can be used for identifying / developing cassava varieties for tolerance to abiotic stress conditions. The study indicated that the plant height of four different cassava varieties were not significantly affected by heat and WDS. The leaf production of four different cassava varieties were significantly affected by both heat and water stress, and the same was maximum in the case of water stress. The leaf retention of four varieties / genotypes were differentially affected by both heat and water stress. There was negligible difference in yield parameters between stress and control condition. However, there was significant difference was yield observed for parameters among the four varieties. The effect of abiotic stress on various physiological parameters like relative water content, chlorophyll and carotenoid content showed significant difference in control plants. Among the given WDS and HTS treatments, the chlorophyll and carotenoid content decreased in all the four varieties. Chlorophyll and carotenoid content were significantly reduced in plants exposed to HTS. Relative water content of leaves varied under both WDS and HTS conditions. A higher RWC was observed in plants exposed to HTS condition compared to WDS condition. Total soluble protein content of leaf and tuber was found to be lower in plants exposed to stress conditions. Total soluble protein in tuber forming roots had increased under HTS conditions. Proline status of plants under stress conditions followed an increasing trend compared to stress conditions. The effect of abiotic stress on various enzymatic antioxidants such asGlutathione Reductase (GR), Superoxide Dusmutase (SOD), Catalase (CAT) and Ascorbate Peroxidase (APX) were studied. Among the four different cassava varieties. Kunguma rose showed maximum GR activity showed an increasing trend in WDS compared to HTS and stress free conditions. Catalase activity of four varieties of cassava plant varied among different stress condition (WDS and HTS) compared to control. The catalase activity was significantly reduced due to stress conditions and. SOD activity increased under stress conditions. The ascorbate peroxidase (APX) activities had significant variation in WDS and HTS compared to control. The AA content in cassava leaves was negligible or below detectable amount under both control and stress conditions. Under HTS condition GR activity increased in H-165 and Sree Athulya alone whereas all the four varieties showed increase GR activity under WDS. Kunguma rose showed maximum SOD activity in HTS whereas Sree Athulya had highest SOD activity in WDS. APX activity was high in all the varieties under HTS. From the present study it is inferred that GR can be used as a biochemical marker for developing WDS tolerant varieties as it showed consistent changes under both WDS and HTS. APX activity can be used as a marker for identifying HTS tolerant varieties. Detailed molecular biochemical and physiological study will be necessary using different varieties for getting appropriate activities as the marker to screen abiotic stress tolerant varieties.