Genetic variability for yield and resistance to chilli thrips (Scirtothrips dorsalis H) and yellow mite(Polyphagotarsonemus latus banks) in chilli(Capsicum annuum L)
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Date
2008
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Department of Plant Breeding and Genetics, College of Agriculture, Vellayani
Abstract
The present study aimed at evaluating a collection of chilli (Capsicum annuum L.) genotypes for yield and resistance to chilli thrips and yellow mite was carried out in the Department of Plant Breeding and Genetics, College of Agriculture, Vellayani during 2006-2007. Fifty genotypes of chilli were evaluated for yield and yield components in a field experiment in randomized block design with three replications. Observations were recorded on 13 characters viz., days to 50% flowering, fruit bearing period, duration, primary branches per plant, secondary branches per plant, plant canopy width, number of fruits per plant, fruit length, fruit girth, fruit weight, number of seeds per fruit and yield per plant. Significant differences existed among genotypes for all the characters as revealed by the analysis of variance. The variety Ca 13 recorded the highest yield per plant (292.88g). Ca 15 was the lowest yielder (74.01g). Ca 10 recorded the highest number of fruits per plant (110.66). The variety Ca 20 recorded maximum plant canopy width (69.55cm). High phenotypic coefficient of variation with correspondingly high genotypic coefficient of variation was observed for number of fruits per plant, fruit yield per plant, secondary branches per plant and primary branches per plant. This indicated the existence of high degree of genetic variation and scope for improvement of these characters through selection. All the characters considered except days to 50% flowering recorded high estimates of heritability. High heritability coupled with high genetic advance was observed for number of fruits per plant, yield per plant and secondary branches per plant. There is immense scope for improvement of these characters through selection on account of their high magnitude of heritability and exceptionally high genetic advance. Fruit yield per plant showed high positive genotypic correlation with number of fruits per plant, duration, length of fruit bearing period, plant canopy width and number of secondary branches. The highest genotypic correlation of yield was with number of fruits per plant. Path analysis revealed that number of fruits per plant had the highest direct effect on yield. The indirect effect of the character via other characters was negligible. Plant canopy width also showed relatively high direct effect as well as positive indirect effect through number of fruits per plant and fruit weight. The study revealed that number of fruits per plant and plant canopy width are important in deciding yield and should be given due consideration in crop improvement programmes. Genetic diversity studies using Mahalanobis D2 statistic indicated considerable diversity among the 50 genotypes of chilli. The genotypes were grouped into eight clusters. Clustering pattern indicated that cluster I is having maximum number of genotypes. Maximum divergence was observed between clusters III and VI. The intracluster distance was the highest for cluster I. Selection indices of the 50 genotypes for yield were worked out using yield per plant and component characters viz., days to 50% flowering, fruit bearing period, duration, primary branches per plant, secondary branches per plant, plant canopy width, number of fruits per plant, fruit length, fruit girth, fruit weight and number of seeds per fruit. Maximum index value was obtained for Ca 13 followed by Ca 22 and Ca 18. Low index values were recorded for Ca 27 and Ca 15. Evaluation of the genotypes for resistance to chilli thrips and yellow mite was done to identify sources of resistance. Population count and leaf damage intensity were the criteria adopted for evaluation of resistance. The genotype that recorded the lowest number of thrips per leaf is Ca 13. Lowest leaf damage intensity was observed for Ca 43. Simultaneous consideration of population count and damage intensity suggested tolerance of Ca13 and Ca 35 to chilli thrips. These varieties are thus identified as promising sources of resistance to chilli thrips. Ca 35 was identified as the variety harbouring the lowest number of yellow mites. Leaf damage due to the mite was low for Ca 6. In view of the relatively low population count and leaf damage, Ca 6 and Ca 35 were identified as genotypes tolerant to yellow mite which can hopefully serve as sources of resistance to the pest. Ca 35 was the only genotype that showed resistance to both chilli thrips and yellow mite. The critical evaluation of the genotypes for tolerance to the pests also confirmed the tolerance of Ca 35 to both of these pests. The study identified Ca 13 as a genotype with high yield potential and tolerance to chilli thrips.
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