1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)

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    Evaluation of pre-sowing interventions on seed quality, storage and field performance of Okra (Abelmoschus esculentus L. Moench)
    (Department of Seed Science and Technology, College of Agriculture, Vellanikkara, 2024-04-09) Adheena, P; Namboodiri Raji Vasudevan
    The research work entitled ‘Evaluation of pre sowing interventions on seed quality, storage, and field performance of okra (Abelmoschus esculentus L. Moench)’, was conducted as two experiments in the Department of Seed Science and Technology, College of Agriculture, Vellanikkara, during 2022-2023. Five months old seeds (variety – Arka Anamika) were subjected to fourteen pre sowing treatments namely, T1-Control, T2-Hydration-Dehydration (12 hours), T3-PEG 6000-13.5% (-0.25Mpa) 6 hours, T4-KNO32%(6hours), T5-sandmatric (60% WHC-3hours), T6-Trichoderma viride 4g/kg of seed, T7-Pseudomonas fluorescens 10g/kg of seed, T8-Hydration-Dehydration (24 hours), T9-PEG 6000-13.5% (-0.25Mpa) 12 hours T10-KNO3 2% (12 hours) T11-sand matrix (60% WHC -6 hours), T12-T.viride 4g/kg+P indica 5x105 spores Ml-1) 10 ml/kg were carried out. The initial seed quality parameters such as germination per cent -94%, vigour index I-1474, vigour index II-2.73, and moisture percent – 7.2 respectively, were assessed before storage and field experiments. In experiment I, the seeds were subjected to eleven of the fourteen presowing treatments mentioned earlier with three replications. These were then dried to less than eight percent moisture, packed in 700g polythene bags and stored under ambient conditions. The observations for all quality parameters were recorded immediately after the treatments and at monthly intervals for six months of storage period. The treatments displayed significant variations across all the investigated seed quality parameters. Among the treatments, treatment T9(PEG 6000-13.5% (-0.25Mpa) 12 hours) recorded the best seed qualities in all months of storage, followed by treatment T4 (KNO3 2% - 6 hours). The storage study clearly demonstrated that the quality of seeds consistently diminished with an extended storage period, regardless of the treatments applied. In the case of germination, all treatments, including control maintained the Indian Minimum Seed Certification Standard (IMSCS) of 65 percent up to the sixth month of storage. Seed quality parameters such as germination percent, vigour index I, vigour index II, seedling length, seedling dry weight and seedling fresh weight decreased with the advancement of the storage period. The electrical conductivity of seed leachate, mean germination time, time taken for 50% germination, seed moisture percent and seed microflora percent were found to be increasing over the period of storage. In experiment II, the seeds were subjected to thirteen treatments and control mentioned earlier. Among these, seven best treatments along with control were selected based on germination percentage and vigor index for the field experiment. The experiment was laid out in RBD (Randomized Block Design), with three replications. Maximum germination percentage was obtained in T4 (PEG 6000-13.5% (-0.25MPa) 6 hours -99.66) and it was on par with T10(Trichoderma viride at 4g/kg of seed), T5(PEG 6000-13.5% (-MPa) 12 hours), T6 (KNO3 2% (6 hours), T3 (hydration-dehydration (24 hours), T9 (sandmatric (60% WHC – 6 hours) and T11 (P. fluorescens at 10g/kg of seed). The results indicated that the pre sowing treatments showed significant differences for all the characters studied. In terms of growth characters, T3 (PEG 6000-13.5% (-0.25MPa) 6 hours) had the maximum number of branches per plant. T8 also had the least number of days to first and 50% flowering. All the fruit characters such as fruits per plant, fruit length (cm), fruit weight (g) at maturity and fruit yield (t/ha) were recorded maximum in treatment T8(P. fluorescens at 10g/kg of seed) which was followed by T7 (Trichoderma viride at 4g/kg of seed). Similarly, all the seed yield characters such as, sees per fruit, seed yield per plant (g) and 100 seed weight(g) were also highest in T8 followed by T7. This underscores the significant impact of biocontrol agents such as P. fluorescens and T. viride on both fruit yield and seed yield characters. The ranking of traits in Experiment II aimed to identify the most effective treatments for enhancing the field performance of okra. Based on the total scores, T8(P. fluorescens at 10 g/kg of seed) emerged as the best treatment followed by T7(T. viride at 4g/kg of seed). In conclusion, treatments T9(PEG 6000-13.5% (-0.25Mpa) 12 hours) and T4 (KNO3 2% (6 hours) were found to be maintaining the seed quality. Additionally, treatments involving P. fluorescens and T. viride proved to be valuable for enhancing fruit yield and seed yield in okra variety Arka Anamika.
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    Biorational management of major pests of Kerala, Abelmoschus esculentus(L.) moench
    (Department of Entomology, College of Agriculture, Padannakkad, 2023-11-13) Gagan, B S.; Ramesha, B
    The study entitled “Biorational management of major pests of okra, Abelmoschus esculentus (L.) Moench” was carried out in the Instructional Farm, Karuvachery during two seasons viz., summer (January to May) and kharif (June to September) in the year 2022 to study the efficacy of different microbial agents, neem based and biorational insecticides against major pests of okra viz., okra shoot and fruit borer, aphids, jassids and leaf roller. Bioassay studies were conducted in the laboratory of Department of Entomology, College of Agriculture, Padanakkad during 2022-23 to evaluate the efficacy of microbial agents, neem based and biorational insecticides against aphids, jassids and leaf roller. Treatments were applied on test insects as three replications and the percentage mortality at fixed intervals was worked out. The field experiment was laid out in randomized block design (RBD) with nine treatments and three replications. The okra variety ‘Salkeerthi’ released by KAU was selected for the study. Treatments included were; T1: Bt formulation 2× 109 cfu/ml @ 10 ml/l of water; T2: Neem based formulation (Azadirachtin 1%) @ 2 ml/l of water; T3: Raksha (Neem oil, garlic, soap based formulation- KAU product) @ 6 g/l of water; T4: Emamectin benzoate 5% SG @ 0.4 g/l of water; T5: Pyridalyl 10 EC @ 1.5 ml/l of water; T6: Flonicamid 50 WG @ 0.6 g/l of water; T7: Spinosad 45 SC @ 0.4 ml/l of water; T8: Malathion 50 EC @ 2ml/l of water- Standard check; T9: Absolute control. Treatments were imposed at 30th, 45th and 65th day after sowing and observations were recorded at weekly intervals corresponding to standard weeks. The data were subjected to square root transformation and analysed using ANOVA in GRAPES (General R-shiny based Analysis Platform Empowered by Statistics) software. Bioassay studies indicated that highest percentage mortality of aphids, jassids and leaf roller were recorded in treatment T6 (Flonicamid 50 WG), T4 (Emamectin benzoate 5% SG) and T7 (Spinosad 45 SC) respectively after 24 hours of treatment application. Analysis of field experimental results showed that there is significant difference between the treatments in reducing the pest status of the crop as well as yield parameters of the crop. After three sprays, treatment T7 (Spinosad 45 SC @ 0.4 ml/l of water) at fortnightly intervals completely reduced shoot and fruit borer larvae in both summer and kharif seasons and leaf roller larvae in kharif season. Therefore, it was found that Spinosad 45 SC was effective in reducing the population of shoot and fruit borer and leaf roller as well as the percentage of shoot and fruit infested. During summer season, treatment T6 (Flonicamid 50 WG @ 0.6 g/l of water) was found to be the most effective treatment in reducing the nymphs and adults of aphids and their percentage shoot infestation in the vegetative phase of the crop. Treatment T4 (Emamectin benzoate 5% SG @ 0.4 g/l of water) and T2 (Azhadirachtin 1% @ 2 ml/l of water) were found effective in controlling the nymphs and adults of jassids in both summer and kharif seasons. T6 (Flonicamid 50 WG @ 0.6 g/l of water) also provided effective control of jassid population in the crop. Among the different treatments, maximum fruit length was recorded in T7 followed by T4 during both summer (17.13 and 15.50 cm) and kharif season (17.32 and 16.10 cm) respectively. Total yield was highest in T7 followed by T4 showing per plant yield of 384.87 and 360.53 g respectively during summer season and 502.65 and 479.47 g respectively during kharif season. Also, the same treatments recorded highest marketable yield of 369.79 and 339.75 g/plant respectively during summer season and 482.91 and 458.83 g/plant respectively during kharif season. During both seasons viz., Summer and kharif, highest benefit-cost ratio was recorded in T4 (2.73 and 3.62) and T7 (2.70 and 3.54) respectively. The results of the investigation clearly indicated that, along with then recommended package of practice, spraying of Spinosad 45 SC @ 0.4 ml/l of water provides effective control of okra shoot and fruit borer and leaf roller without reducing the marketability of the fruits. Spraying of Flonicamid 50 WG @ 0.6 g/l of water can be used to effectively control the sucking insects like aphids and also jassids. Emamectin benzoate 5% SG @ 0.4 g/l of water and Azadirachtin 1% @ 2 ml/l of water can be used to control nymphs and adults of jassids on okra
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    Eco-Friendly Weed Management in Okra (Abelmoschus Esculentus (L.) Moench)
    (Department Of Agronomy College Of Agriculture, Vellayani, 2021-10-13) Seethal Rose Chacko; Sheeja K Raj
    The study entitled “Eco-friendly weed management in okra (Abelmoschus esculentus (L.) Moench) was carried out during the period 2019-2021, at College of Agriculture, Vellayani, Thiruvananthapuram, Kerala with an objective to find out a cost -effective ecofriendly weed management practice for okra. The field experiment was conducted at Coconut Research Station, Balaramapuram, Thiruvananthapuram, Kerala during Rabi 2020 (November 2020- March 2021). The experiment was laid out in randomized block design with 12 treatments replicated thrice. The treatments were combinations of two factors, first factor being seedbed preparation (S), viz., stale seedbed (S1) and normal seedbed (S2) and second factor, weed management practices (W) viz., dried banana leaf mulch @ 10 t ha-1 alone (W1), dried banana leaf mulch @10 t ha-1 fb mechanical weeding (MW) with wheel hoe weeder (WHW) at 30 DAS and 45 DAS (W2), dried banana leaf mulch @10 t ha-1 fb hand weeding (HW) at 30 and 45 DAS (W3), MW with WHW at 15, 30 and 45 DAS (W4), HW at 15, 30 and 45 DAS (W5) and weedy check (W6). The variety used for the study was Anjitha. Results of the experiment revealed that seedbed preparation had significant influence on growth parameters, physiological parameters, yield attributes and quality parameters in okra and higher values were recorded in SSB. At 15, 30 and 60 DAS, lower total density of weeds (30.44, 90.67 and 35.67 no. m-2), weed dry weight (0.139, 4.57 and 7.81 g m-2) and higher weed control efficiency (WCE) (80.20, 89.46 and 81.33%) were recorded in SSB compared to normal seedbed. The highest nutrient uptake by crop, dehydrogenase enzyme activity at 60 DAS and urease enzyme activity at 15, 30 and 60 DAS and the lowest nutrient removal by weeds at 30 and 60 DAS were recorded in SSB. Higher net income (54,520 ₹ ha-1) and B:C ratio (1.69) were recorded in SSB compared to normal seedbed (non-stale). Higher values for growth parameters viz., plant height, number of branches per plant, number of leaves per plant, dry matter production and physiological parameters such as LAI, total chlorophyll content at 60 DAS and CGR at 30-60 DAS time interval were recorded in MW with WHW at 15, 30 and 45 DAS (W4). However, the treatment W5 (HW at 15, 30 and 45 DAS) resulted in the highest total chlorophyll content at 30 DAS and W2 (dried banana leaf mulch @ 10 t ha-1 fb MW at 30 and 45 DAS) resulted in the highest CGR during 60 DAS-final harvest. Mechanical weeding with WHW at 15, 30 and 45 DAS recorded greater number of fruits per plant (38.8 no. per plant), higher fruit girth (6.36 cm), fruit length (15.20 cm), fruit weight (6.98 g), dry haulm yield per plant (63.51 g), dry haulm yield per hectare (2353 kg ha-1), fruit yield per plant (0. 270 kg) and fruit yield per hectare (4412 kg ha-1) and the lowest weed index. Quality parameters such as crude protein and ascorbic acid content was higher in treatment W2 (dried banana leaf mulch @ 10 t ha-1 fb MW at 30 and 45 DAS). The lowest total weed density at 60 DAS (26.67 no. m-2), the lowest total weed dry weight at 30 and 60 DAS (2.48 and 2.54 g m-2, respectively) and the highest WCE at 30 and 60 DAS (92.28 and 93.86 %, respectively) were recorded in MW with WHW at 15, 30 and 45 DAS (W4). The highest nutrient uptake by crop and the lowest nutrient removal by weeds was recorded in the treatment W4. The highest net income (97,804 ₹ ha-1) and B: C ratio (2.24) were recorded in W4 (MW with WHW at 15, 30 and 45 DAS). Interaction between seedbed preparation and weed management practice was significant only for plant height at 60 DAS and final harvest, DMP at 30 and 60 DAS, LAI at 60 DAS and CGR at 30-60 DAS and total weed density, weed dry weight, WCE and nutrient removal by weeds at 30 and 60 DAS. Stale seedbed fb MW with WHW resulted in the lowest total weed dry weight and the lowest nutrient removal by weeds. Considering the growth, yield, weed control efficiency, nutrient removal by weeds, nutrient uptake by crop and economics, it could be concluded that in SSB or in normal seedbed (non-stale), mechanical weeding with wheel hoe weeder at 15, 30 and 45 DAS could be adjudged as the best ecofriendly weed management practice for higher yield and net income in okra
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    Herbigation in Okra (Abelmoschus esculentus (L.) Moench)
    (Department of Agronomy, College of Agriculture, Vellanikkara, 2021) Minu, Mariya Issac; Mini, Abraham
    Herbigation is the method of application of herbicides through irrigation water. Conventional method of herbicide application takes considerable time and expensive due to the increasing cost of manual labour. Also, heavy wind at the time of spraying and improper application causes more herbicide loss, environmental pollution and drift injury to the nearby fields especially on sensitive crops. Herbigation ensures no additional costs of application. Okra is one of the important vegetable crop of Kerala. Weed competition during early stage of crop growth significantly lowers crop yields. Heavy weed infestation in okra is mainly due to wider spacing, slower crop growth during early stages, high fertilizer use and frequent irrigation. Therefore, the present study was undertaken with a view to study the effect of herbigation through drip irrigation system in okra and also to evaluate the economic feasibility of the system. The experiment was conducted at Water Management Research Unit, Vellanikkara from December 2019 to April 2020. The experiment was laid out in RBD with ten treatments and three replications. Treatments comprised of herbigation and conventional spraying of oxyfluorfen applied in two doses (0.15 kg ha-1 & 0.20 kg ha-1) at two different time of application , a hand weeded control and an unweeded control. The okra variety used was Arka Anamika. Predominant grasses seen in the plots were Panicum maximum, Digitaria sanguinalis, Brachiaria miliformis, Digitaria bicornis and Axonopus compressus. Predominant broad leaved weeds were Ageratum conyzoides, Euphorbia hirta, Mollugo disticha, Cleome burmanii, Trianthema portulacastrum, Alternanthera bettzickiana, and Synedrella nodiflora. The sedges present were Cyperus spp., and Bulbostylis barbata in the experimental field. Observations on weed count showed that application of oxyfluorfen was effective in controlling both grass and broad leaved weeds. Maximum weed control efficiency was observed in conventional spraying with oxyfluorfen @ 0.20 kg ha-1 two days before sowing followed by hand weeding at 30 DAS with 91.31 per cent at 20 DAS; conventional spraying with oxyfluorfen @ 0.15 kg ha-1 two days before sowing followed by hand weeding at 30 DAS with 90.08 per cent at 50 DAS and hand weeded control recorded 90.59 per cent at 80 DAS. Lowest weed index was recorded from herbigation with oxyfluorfen @ 0.15 kg ha-1 two days before sowing followed by hand weeding at 30 DAS followed by the treatment conventional spraying with oxyfluorfen @ 0.15 kg ha-1 two days before sowing followed by hand weeding at 30 DAS. Even though, conventional spraying recorded lesser weed count and weed dry weight, the yield was less due to the scorching of crop foliage. During herbigation, herbicide is applied through drip to the crop root zone, due to which weeds in the interspaces that can germinate in water stress conditions will grow. While in conventional spraying, the entire cropped area come in contact with herbicide and results in complete control of weeds. The nutrient removal by weeds was maximum in unweeded control. Herbigation with oxyfluorfen @ 0.15 kg ha-1 two days before sowing followed by hand weeding at 30 DAS was on par with hand weeded control in terms of plant height, number of leaves and leaf area. It also recorded highest number of fruits per plant (17.8), average fruit weight (13.73 g), fruit yield per plant (243.90 g) and fruit yield (13.02 t ha-1). It was on par with hand weeded control (13.04 t ha-1), conventional spraying with oxyfluorfen @ 0.15 kg ha-1 two days before sowing followed by hand weeding at 30 DAS and herbigation @ 0.20 kg ha-1 two days before sowing followed by hand weeding at 30 DAS. Weed competition resulted in 58.97 per cent yield reduction in okra. Unweeded control recorded significantly lower fruit yield (5.35 t ha-1). Both conventional spraying and herbigation with oxyfluorfen @ 0.15 kg ha-1 two days before sowing followed by hand weeding at 30 DAS were equally effective in controlling weeds. Herbigation with oxyfluorfen @ 0.15 kg ha-1 two days before sowing followed by hand weeding at 30 DAS resulted in higher gross return, net return and B: C ratio (1.97) which was closely followed by conventional spraying with oxyfluorfen @ 0.15 kg ha-1 two days before sowing followed by hand weeding at 30 DAS (1.89). The result of the study revealed that the farmers can adopt either herbigation or conventional spraying of oxyfluorfen according to their convenience because both treatments performed equally well. Herbigation can be implemented in fields in which already fertigation is carried out because it doesn’t involve any additional costs.
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    Standardisation of operational procedures for pro-tray seedling production of vegetables
    (Department of Vegetable Science, College of Agriculture, Vellanikkara, 2022) Arya, S; Dicto Jose, M
    Healthy seedlings are the most important prerequisite for any vegetable crop to reach its full output potential. As a result, large-scale seedling production is becoming a profession and a commercial activity. Farmers used to generate seedlings at a reasonable cost in nursery beds in the past. However, due to some drawbacks like poor germination, higher pest and disease incidence, poor field establishment etc. in traditional nurseries, many progressive farmers and agriculture entrepreneurs have turned their attention to the commercial production of quality seedlings utilising seedling trays or pro-trays. In this background, the present study entitled ‘Standardisation of operational procedures for pro-tray seedling production of vegetables’ was undertaken with the objective of standardising best growing media, pre-sowing seed invigoration, and evaluating the effect of biofertilizer on pro-tray seedling production of vegetables. The present study was carried out at the Department of Vegetable Science, College of Agriculture, Vellanikkara as three experiments during 2020-21. All three experiments were conducted in a Completely Randomized Design with three replications. In the first experiment seeds of tomato var. Anagha, chilli var. Anugraha, cucumber var. Heera, and okra var. Salkeerthi collected from the Department of Vegetable Science were sown in seventeen different media that were initially analysed for various physicochemical properties. The growth parameters of the seedlings raised in the poly house were assessed at the stage of commercial sale of each crop i.e., 15 days after sowing (DAS) in cucumber and okra and 30 DAS in chilli and tomato. The results showed that T13 (cocopeat: vermiculite: perlite - 1:1:1) and T17 recorded comparatively minimum bulk density, maximum water holding capacity and porosity which are desirable physical properties for good seedling growth. T17 (coir pith compost: vermiculite: perlite - 3:1:1) was found to be the best soil-less media for all four crops based on growth parameters and cost analysis. Among soil containing media T6 having soil and dried powdered cow dung in equal proportion and T10 having soil, cocopeat and dried cow dung exhibited a higher benefit cost ratio and was found to be on par with T17 for most of the growth parameters. Farmers do not have easy access to vermiculite and perlite, and they are costly. In this context, soil, cocopeat and dried powdered cow dung in equal proportion is found to be an alternate media comprising locally available inputs and affordable by the farmers. The best media from the first experiment was chosen for further trials. The second trial comprised of nine different seed treatments including various concentrations of KNO3 and Pseudomonas. Pre-sowing seed invigoration with 0.5% KNO3 in combination with 1% Pseudomonas was found to be highly effective in improving germination and growth parameters viz., germination percentage, plant height, root length, vigour index Ⅰ & Ⅱ and chlorophyll content of seedlings of tomato, chilli, cucumber and okra. This combination has the dual advantage of providing potassium and nitrogen to the seedlings and imparting resistance from diseases especially damping off. So, these treatments can be effectively utilized for producing healthy and vigorous vegetable seedlings. The third experiment included nine treatments in which different biofertilizers viz., PGPR Mix-1, Pseudomonas fluorescense, Trichoderma asperellum and arbuscular mycorrhizal fungi were inoculated in the media individually and in combination. Evaluation of the effect of biofertilizers showed that higher growth parameters like plant height, root length, leaf area, collar girth, vigour index Ⅰ and vigour index Ⅱ are comparatively higher in the treatment containing PGPR, AMF and along with either Pseudomonas or Trichoderma. In the above three experiments the best treatments were identified by ranking based on an index derived from principal component analysis. The characters viz., number of leaves, leaf area, collar girth, vigour index Ⅰ & Ⅱ and total chlorophyll content was used for performing PCA. The loadings of principal component having Eigen value more than one was taken as weightage. Using weightage, an index was derived and the treatments having higher index was ranked higher. The best media obtained include cocopeat: vermiculite: perlite (3:1:1) and soil: cocopeat: cow dung (1:1:1). A combination of 0.5% KNO3 and 1% Pseudomonas was the best seed invigoration treatment. Among different biofertilizers evaluated the combination of AMF, PGPR Mix-1 and Pseudomonas was found to be the best. Based on the insights of the above three trials, standard operational protocol for seedling production of tomato, chilli, cucumber and okra is generated for use by farmers.
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    Drought mitigation in Okra (Abelmoschus esculentus L.) through chemical approach
    (Department of Plant Physiology, College of Agriculture, Padannakkad, 2021) Fathimath Suhaila; Sudarsana Rao, G V
    Okra 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.
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    RNA mediated resistance to Yellow vein mosaic virus in okra
    (Centre for Plant Biotechnology and Molecular Biology, College of Agriculture, Vellanikkara, 2021) Kelkar Vipul Ganesh; Deepu Mathew
    Okra (Abelmoschus esculentus L. Moench, Malvaceae) is one of the leading vegetable crops in hot and humid tropics. Unfortunately, this climate is conducive for many of the pests and diseases. Okra is susceptible to viruses such as Yellow vein mosaic virus (YVMV) and Enation leaf curl virus (ELCV), belonging to the genus Begomovirus (family Geminiviridae). Because of the favourable conditions prevailing in the coastal region, the losses in Kerala state are 60-100%, depending upon the stage of plant growth and the severity of infection. RNAi is one of the promising molecular biology approach against the viral diseases. Keeping the above facts in view, the present study “RNA mediated resistance to Yellow vein mosaic virus in okra” was taken up at the Centre for Plant Biotechnology and Molecular Biology, CoA, Thrissur from September 2017 to May 2021. The high yielding and YVMV susceptible popular okra cv. Salkeerthi was selected for the development of resistance using RNAi mechanism. Total DNA was isolated from the YVMV infected plant and part of the βC1 gene (187 bp) of the virus was amplified using primers VβC1F and VβC1R. Sequence information of PCR product has revealed that the gene is 90-95% identical with the Indian isolates. The βC1 gene sequence was analysed using IDT software and 10 siRNAs were found at three different position (19-44, 34-59, 99-124 bp). Through Restriction Mapper, it was confirmed that the sequence selected for the preparation of sense and antisense strand, do not possess recognition sites for SmaI, HindIII and MauBI restriction enzymes which are present in the pRNAiLIC vector. The output of VSupPred revealed that the fragment does not contain any Viral Suppressor Regions (VSRs), with a high prediction score (0.625). The hairpin RNAi construct harbouring the region of βC1 gene of β satellite of Begomovirus of okra was generated using pRNAi-LIC (CD3-1285) vector. The SmaI digested plasmid produced three fragments, vector backbone (9842 bp), Pdk intron (1641 bp) and ccdB gene (614 bp) and the digested plasmid was treated with dTTP. Product-1 was PCR amplified (215 bp) with VLIC1 and VLIC2 primers, using the DNA from YVMV infected plant as template. Product-2 was PCR amplified (243 bp) with VLIC3 and VLIC4 primers using product-1 as template. Product-1 and product-2 were eluted from the gel and treated with dATP. The dATP treated PCR products and dTTP treated SmaI digested plasmid were mixed together and ligated by incubation at 65ºC for 5 min. followed by 22ºC for 15 min. Ligated product was successfully transformed in competent cells of E. coli (DH5α) and incubated on LB medium containing Kanamycin and Chloramphenicol. Colony PCR was performed, the transformation efficiency was found to be 80%. Plasmid was isolated from the positive DH5α colony and sequenced using the primers VLIC5 and VLIC6. The sequence data had shown that both sense and antisense strands are at right position and direction. Plasmid containing ihpRNA-βC1 cassette was successfully transformed into the competent cells of Agrobacterium (GV3101) and incubated on LB medium containing Kanamycin, Chloramphenicol and Rifampicin. Colony PCR was performed, the transformation efficiency was found to be 100%. Plasmid was isolated from the positive GV3101 colony and sequenced using the primers VLIC5 and VLIC6. Sequence data has further confirmed that both sense and antisense strands are at right position and direction. The ihpRNA-βC1 cassette was successfully transformed into okra cv. Salkeerthi using in planta method of Agrobacterium mediated transformation. The transformation efficiency observed was 11.42% and the transformation was confirmed by the amplification of sense strand using the primers VLIC1 and VLIC5. cDNA was prepared from the total RNA isolated from transformed and control plants. siRNA synthesis was confirmed using the primers VLIC1 and VLIC5 (400bp) and Ubiquitin gene was confirmed using the primer UBQ7 (187 bp). Silencing potential of the RNA interference of βC1 gene and the development of resistance was evaluated by keeping the 15-day old transformed and control plants along with YVMV infected plants inside containment facility, with whiteflies released into insect cage for infection. All the control plants and one transgenic plant have shown the YVMV symptoms after 10 days. Three transgenic plants were healthy with no symptoms. The present investigation was successful in the development of YVMV resistant okra plants carrying ihpRNA-βC1 using pRNAi-LIC (CD3-1285) plasmid vector. The further evaluation is needed in the coming generations for the identification of stable transgenic lines.
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    Breeding for yellow vein mosaic virus (YVMV) resistance in OKRA (Abelmoschus esculentus (L.) Moench)
    (Department of Vegetable Science, College of Horticulture, Vellanikkara, 2020) Alphy Mathew; Pradeepkumar, T
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    Management of bhendi yellow vein mosaic virus using beneficial fungal root endophyte Piriformospora indica
    (Department of Plant Pathology, College of Agriculture, Vellayani, 2020) Chippy; Joy, M
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    Pilot testing of fertilizer manure blocks in okra (Abelmoschus esculentus L. Moench.)
    (Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2020) Induja, M; Thulasi, V