MSc

Chilli (Capsicum annuum L.), is one of the most important vegetables as well as spice grown in tropical and subtropical regions. However, the productivity of chilli is adversely affected by insect complex especially aphids, thrips and mites. Chemical management of mites are often not encouraged due to negative consequences such as residue in harvested produce, pesticide resistance and various other environmental problems. Development of resistant varieties that utilize plant defence mechanisms is the sustainable solution. In this context, the present study entitled Identification of yellow mite resistant lines in early segregating generations of chilli was carried out during 2024. Previous study conducted at the Department of Plant Breeding and Genetics, Vellanikkara had identified three moderately mite resistant chilli hybrids viz., Anugraha x 417, Anugraha x 445, and 451 x 445. F2 and F3 generations of above three crosses along with their parents served as the experimental material for the present study. Varieties viz., Anugraha and Ujwala were used as checks. F2 generation of the above three hybrids each with a population size of 200 plants were raised for evaluation. Hundred plants belonging to F2 generation of each cross were raised in the open field condition and the remaining 100 plants under the polyhouse. Parents involved in the above crosses were similar in qualitative characters such as hypocotyl colour, cotyledonous leaf colour, stem colour, nodal anthocyanin, leaf colour, leaf shape, flower position, corolla colour, anther lobe colour, filament colour, stigma exertion, calyx pigmentation, anthocyanin spots on fruits, fruit colour at intermediate stage, fruit shape, mature fruit colour, fruit blossom end appendage, fruit cross-section corrugation, fruit surface, seed colour and seed surface. So, there was no variation for these traits in the F2 generation. Corolla shape and fruit shape at the blossom end segregated in 9:7 ratio in the F2 generation revealing complementary gene interaction involving two genes. Segregating lines from the F2 populations were superior to checks and parental lines in terms of early flowering, early fruiting, fruit length, fruit girth, fruit weight, number of fruits per plant and yield per plant. F2 population raised in the open field condition had more variability than that under the polyhouse. High heritability coupled with high genetic advance as percentage of the mean were recorded for days to flowering, fruit girth, fruit weight, number of fruits per plant and yield per plant suggesting the predominance of additive gene action in inheritance of these traits. Under polyhouse conditions, days to flowering and days to fruiting as well as fruit length and girth under open field conditions exhibited leptokurtic distributions. Conversely, under open field conditions, days to flowering and days to fruiting along with fruit length and girth under polyhouse conditions exhibited platykurtic distributions. Most of the traits except days to flowering and days to fruiting, expressed positively skewed distribution revealing complementary gene action in the expression of those traits. Artificial release of mites was carried out at 30 days after transplanting (DAT) by leaf clipping and scoring of mite resistance was done according to Niles (1980), and Latha and Hanumanthraya (2018) at 45, 60 and 75 DAT. Percentage of leaves exhibiting downward curling symptoms (PLDC) ranged from 4.13 to 83.80 in the F2 generation, whereas it was in the range of 24.37 to 65.84 in the checks. Among the segregating generation, PLDC ranged from 9.01 to 80.79 under the polyhouse condition, whereas it was in the range of 4.13 to 83.80 in the open field. There was no immune genotype in the F2 generation. Based on the PLDC, there were 106 resistant, 281 moderately resistant, 201 susceptible, and five highly susceptible genotypes. Mite population was recorded from the resistant and moderately resistant genotypes at 75 DAT. Total number of eggs and active stages of mites ranged from zero to 13.25/cm2 on leaves of resistant genotypes under the polyhouse. Resistant and moderately resistant F2 plants were selected and forwarded to F3 generation as progeny rows. In the F3 generation, PLDC varied between 3.33 and 89.47. There were significant differences between the progeny rows with respect to PLDC. Based on the PLDC at 75 DAT, selection was carried out within and between the progeny rows. Out of 1260 genotypes in the F3 generation, 129 were resistant and 390 were moderately resistant at 75 DAT. Total number of mite eggs and active stages on resistant plants ranged from zero to 55.00/cm2 at 75 DAT. The resistant lines identified from this study could be used as new varieties or as parents in the hybridization programme after attaining homozygosity.