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Item Characterization of resistance in tomato (Solanum lycopersicum L.) genotypes against whitefly (Bemisia tabaci genn.)(Department of Agricultural Entomology, College of Agriculture, Vellanikkara, 2023-02-23) Kattumulla Tejaswee.; Ranjith, M T: Tomato, Solanum lycopersicum (Mill.), is one of the most popular vegetables cultivated in tropical and subtropical regions of the world. In India, it has been cultivated across an area of 841 thousand ha, with a production of 20.38 metric tonnes (Statista, 2022). However, tomato production is hindered by various abiotic and biotic factors and among the biotic factors, the polyphagous sucking insect pest, whitefly, Bemisia tabaci (Genn.) causes both direct and indirect damage and yield loss to the tune of 25-100 per cent (Mutisya et al., 2016). Both nymphs and adults of B. tabaci feed on phloem sap and devitalizes the tomato plants and also serves as a vector for the causal organism of tomato leaf curl virus disease. To manage the whitefly menace in tomato, farmers rely heavily on chemical insecticides. However, the polyphagous nature of the insect as well as its innate ability to develop resistance to insecticides makes the management of the pest all the more difficult. Exploiting host plant resistance could be an alternative tool to manage whitefly infestation in tomatoes. Thus, the present study entitled “Characterization of resistance in tomato (Solanum lycopersicum L.) genotypes against whitefly (Bemisia tabaci Genn)” was undertaken in the Department of Entomology, College of Agriculture, Vellanikkara, Kerala Agricultural University, Thrissur during 2021-2022. 50 tomato genotypes obtained from different institutes viz., IARI, IIHR, NBPGR, KAU, TNAU and local collections were screened for whitefly resistance under polyhouse conditions. The tomato genotypes showed significant variation with respect to eggs, nymphal and adult populations of whitefly. The mean (pooled) number of eggs per plant varied between 1.63 and 7.28 eggs/cm2 and within the plants, the highest mean number of eggs was recorded on the top leaves (8.20 eggs/cm2), followed by the middle leaves (7.40 eggs/cm2), and the bottom leaves (6.30 eggs/cm2). Whereas, the mean (pooled) number of nymphs per plant varied from 1.45 to 7.41 nymphs/cm2 and within the plant, the highest number of nymphs was observed on the middle canopy (6.53 nymphs/cm2) followed by upper (5.84 nymphs/cm2) and bottom (4.62 nymphs/ cm2) parts of the canopy. However, the mean (pooled) number of adult whiteflies per plant ranged from 1.68 to 7.19 adults/ cm2 and within the plant, the highest number of adults were recorded on the upper canopy (8.20 adults/ cm2), followed by middle (7.20 adults/ cm2) and the bottom (5.90 adults/ cm2). Further, the genotypes were categorized based on scale given by Pradhan (1964). Three genotypes LC Idukki, LC Palakkad and EC 519806 which recorded the mean population of active stages of whitefly <3.67/ cm2 come under the resistant category, whereas eleven genotypes with a mean population ranging from 3.67 to 5.57 were categorised as moderately resistant. Sixteen genotypes were classified under the moderately susceptible category with a mean population ranging from 5.57 to 7.46, whereas 18 genotypes with a mean population >7.46 were considered as the highly susceptible category. The leaf area damage due to the feeding activity of whitefly, which results in the degradation of chlorophyll was measured indirectly in terms of the hue value of scanned photographic images of the leaves represented as integrated densities. The tomato genotypes classified under the resistant category recorded a low hue value ranging from 47 to 53, whereas in the susceptible genotypes, the hue value reached up to 99.5. Morphological characters like the type, length and density of trichome, and leaf lamina thickness were analyzed. Observation of the trichome type revealed that LC Idukki and LC Palakkad possessed three types of trichome i.e., type IV (glandular), type V (nonglandular), and VI (glandular). The length of the non-glandular trichome (Type V) present in the tomato genotypes varied from 513.10 μm to 1475.05 μm. The non-glandular trichome and glandular trichome densities recorded in the tomato genotypes ranged between 30.5 to 74.5 per mm2 and 5.50 to 98.00 per mm2, respectively. Leaf lamina thickness was measured and it ranged from 233.20 μm to 440.5 μm. There was a significant positive correlation between the whitefly population and the parameters such as nonglandular trichome density, leaf lamina thickness and length of trichome. However, a significant negative correlation exists between and glandular trichome density and whitefly population and it is presumed that the trichome type IV and VI present in the genotypes confers resistance to whitefly infestation. The biochemical parameters such as relative leaf water content (91.16 %), and total amino acid content (3.58 mg g-1) were found to be low, whereas, the total phenol (4.56 mg/ g), total flavonoid (1.82 𝜇𝑔 gˉ¹), and total alkaloid content (0.59 mg g-1) were significantly higher in resistant genotype LC Idukki. It was found that there was a significant positive correlation between the whitefly population and parameters such as relative water content and total amino acid content, whereas a significant negative correlation was observed between the whitefly population and parameters such as total phenol, flavonoid and alkaloid contents. Based on the present investigation, LC Idukki, LC Palakkad and EC 519806 may be rated as resistant to whitefly. The studies also show that resistance could be mediated by the type, density and length of leaf trichomes, along with leaf lamina thickness. It also indicated that the resistance in tomato to whitefly could be related to biochemical constituents of the plant, which, however, need to be confirmed. Sustained efforts could lead to the development of whitefly resistant tomato genotypes, providing the muchneeded edge to whitefly management in tomatoes.Item Nutrient based management of chilli leaf curl virus in Chilli (Capsicum annuum L.)(Department of Plant Pathology, College of Agriculture, Vellayani, 2019) Shilpa Sankar; Radhika, N SThe study entitled “Nutrient based management of Chilli leaf curl virus in Chilli (Capsicum annuum L.) was conducted at Department of Plant Pathology, College of Agriculture, Vellayani from 2017 to 2019. The main objectives were to serologically and molecularly characterize the virus causing leaf curl in chilli and to study the role of nutrient application in the management of the disease. The present investigation was carried out in four experiments viz., collection of Begomovirus infecting chilli from different cultivated areas, symptomatology, serological diagnosis and molecular characterization of the virus causing chilli leaf curl and nutrient based management of chilli leaf curl. The survey was undertaken from December 2018 to March 2019 to investigate the disease incidence in major chilli growing areas of Palakkad (Vadakarapathy and Kozhinjanpara) and Thiruvananthapuram districts (College of Agriculture, Vellayani) of Kerala. In Thiruvananthapuram, the disease incidence ranged from 69.33 to 80 per cent whereas Palakkad recorded maximum incidence of 73.33 per cent in Vadakarapathy village and Kozhinjanpara village recorded the disease incidence of 55.71 to 71.70 per cent. The common symptoms of the disease were upward curling and puckering of leaves, and stunting of whole plant. Other symptoms viz., reduced leaf size, yellowing, petiole elongation, crinkling and mottling of leaves with few or no fruits were also observed. Serological diagnosis of the disease was carried out using triple antibody sandwich – enzyme linked immunosorbent assay (TAS-ELISA) using polyclonal antisera specific to Begomovirus, Sri Lankan cassava mosaic virus (SLCMV). All the samples collected from College of Agriculture, Vellayani were detected with the virus whereas none of the samples from Palakkad district were positive to the virus. Molecular characterization of the virus using universal primers specific to coat protein of Begomovirus viz., AV-AC and DENG through Polymerase chain reaction (PCR) revealed that the DNA isolated from samples of Vellayani could yield an amplicon size of ̴ 550 bp (AV-AC) and ̴ 500 bp (DENG); thus confirming the presence of the virus. But no PCR amplification was observed in any of the samples from Palakkad district. Blast analysis with the sequence of coat protein of Vellayani revealed that the virus had 96.63 per cent similarity with Chilli leaf curl Vellanad virus. Nutrient status of healthy and diseased leaves revealed that the per cent of major nutrients viz., nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg); and micronutrients viz., manganese (Mn), zinc (Zn), copper (Cu) and boron (B) in the infected leaves was low compared to the healthy leaves but in sufficient level. Whereas, the per cent of sulphur (S) and iron (Fe) in infected leaves was high and in toxic level. Comparatively higher levels of all the major and micro nutrients were recorded in the soils collected from the infected fields than the soils from the healthy field. A pot culture study was conducted at Department of Plant Pathology in completely randomized design consisting of ten treatments and three replications with chilli variety Vellayani Athulya from May 2019 to August 2019. Cent per cent disease incidence was recorded in all chilli plants before imposing the treatments. Soil samples were taken and analysed for major and micro nutrients at pre-treatment stage. Urea, rajphos, murate of potash, lime and magnesium sulphate (MgSO4) were used as the source of major nutrients like N, P, K, Ca and Mg, respectively. Whereas, manganese sulphate (MnSO4), zinc sulphate (ZnSO4), copper sulphate (CuSO4), borax and potassium silicate were used as source for micronutrients such as Mn, Zn, Cu, B and Si, respectively. After imposing the treatments, the highest coefficient of infection (75.0) was recorded in untreated infected plants whereas, the plants supplemented with nutrients as per package of practices (POP) + B @ 10 kg ha-1, POP + (ZnSO4) @ 20 kg ha-1 and, basal application of 1/2 N + full P + 1/2 K followed by 0.5 per cent foliar application of NPK 19:19:19 at fortnightly recorded the lowest coefficient of infection (25.0). TAS-ELISA conducted with all the experimental plants confirmed the presence of virus. Lower virus titre value was observed in the plants supplemented with nutrients as per POP recorded maximum level of major nutrients. Among the treatments highest fruit yield of 48.85 g plant1 was obtained from plants supplemented with nutrients as per POP + B @ 10 kg ha-1 was found to be most effective in reducing the coefficient of infection with better yield. Thus, the present study revealed that the serological diagnosis of the disease carried out using TAS-ELISA with antisera SLCMV and molecular characterization of the virus using primers AV-AC and DENG through PCR confirmed the presence of virus in Vellayani. The BLAST analysis of Chilli leaf curl Vellayani isolate thus showed 96.63 per cent similarity with Chilli leaf curl Vellanad virus. It was also indicated that Chilli leaf curl virus in chilli could be managed by the application of nutrients as per package of practices recommendation along with boron as borax @ 10 kg ha-1 which need to be validated under field conditions.Item Management of sucking pests of brinjal (Solanum melongena L.)(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2015) Arya, V C; Anitha, NAn investigation on “Management of sucking pests of brinjal (Solanum melongena L.)” was carried out at College of Agriculture, Vellayani during 2013-2014. The objectives were to assess the intensity of damage caused by sucking pests in brinjal and evolve a suitable management strategy using newer insecticides. Survey conducted in 60 homesteads of vegetable growing tracts of Thiruvananthapuram district revealed the incidence of seven sucking pests namely leaf hopper, Amrasca biguttula biguttula (Ishida), aphid, Aphis gossypii Glover, whitefly, Bemisia tabaci Gennadius, spiralling whitefly, Aleurodicus dispersus, brinjal mealy bug, Coccidohystrix insolita Green, lace wing bug, Urentius hystricellus (Richt) and mite, Tetranychus sp. on brinjal grown in garden land and terrace. The leaf hopper, aphid, whiteflies and mealy bug were the major sucking pests infesting brinjal in the garden land and terrace during the vegetative and flowering stages. The infestation of the leaf hopper was recorded from all the locations surveyed and aphid, whitefly (B. tabacii) and mealy bug in 89.17, 86.67 and 85 per cent homesteads respectively. The damage caused by the pests ranged from 35.35 to 58.88, 30.11 to 40.24, 34.46 to 50.50 and 34.16 to 49.28 per cent by leaf hopper, B. tabacii, aphid and mealy bug respectively. A predator viz., Spalgis epius (Westwood) and a pathogen Fusarium sp. were isolated from the mealy bug, C. insolita. Two field trials conducted to evaluate the efficacy of the new generation insecticides viz., spiromesifen 96 g ai ha-1, thiamethoxam 50 g ai ha-1, acetamiprid 10 g ai ha-1, dinotefuran 30 g ai ha-1, dimethoate 600 g ai ha-1 and biopesticides viz., oxuron 5ml l-1 and Beauveria bassiana 20 g l-1 revealed that the new generation insecticides reduced the population of sucking pests significantly. Thiamethoxam 50 g ai ha-1 resulted in significant reduction in the population of leaf hopper (1.10 plant-1) and was on par with spiromesifen 96 g ai ha-1 (1.12 plant-1) in the first crop. Spiromesifen treated plot recorded highest yield of 10.36 kg plot-1 and it was on par with thiamethoxam (9.56 kg plot-1). Spiromesifen 96 g ai ha-1 reduced the population of whitefly (1.13 plant-1) and it was on par with thiamethoxam 50 g ai ha-1 (1.34 plant-1) in the second crop. Highest yield was also recorded from spiromesifen 96 g ai ha-1 treated plot (10.95 kg plot-1) followed by thiamethoxam 50 g ai ha-1 (9.42 kg plot-1). The results of the study thus indicated that the leaf hopper A. biguttula biguttula and whitefly B.tabaci were the predominant sucking pests infesting brinjal in the homesteads of Thiruvananthapuram district. The new generation insecticides viz., spiromesifen 96 g ai ha-1 and thiamethoxam 50 g ai ha-1 can be used as alternatives to the highly toxic conventional insecticides against the sucking pests, leaf hopper and whitefly.