Screening for leaf curl virus disease complex resistance, genetic evaluation and molecular characterization of bird chilli (Capsicum frutescens L.)

Abstract

The investigation entitled “Screening for leaf curl virus disease complex resistance, genetic evaluation and molecular characterisation of bird chilli (C. frutescens L.)” was conducted at Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, Thiruvananthapuram during 2003-2005. The data for the investigation were collected from two field experiments, each laid out in Randomized Block Design with three replications. The second experiment was conducted without taking any control measures against leaf curl virus disease. The 49 genotypes included in the study showed significant difference for all the 14 biometric characters. They all showed high heritability coupled with high genetic advance except days to first flowering for which the genetic advance was moderate. The maximum values for phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) were recorded for fruit yield per plant and individual fruit weight respectively and the minimum values for days to first flowering. Fruit yield per plant was positively correlated with number of fruit per plant, number of secondary branches, plant spread, 100-seed weight, number of primary branches, number of seeds per fruit, individual fruit weight, fruit length, fruit width and plant height. Path analysis revealed high positive direct effect of individual fruit weight and number of fruits per plant on yield per plant. Hence selection for these characters can improve the yield. The 49 genotypes were grouped into five clusters based on Mahalanobis D2 statistic. Cluster I was the largest with 29 genotypes while clusters IV and V had only one genotype each. Clusters II and III had 11 and eight genotypes respectively. Cluster I was found to be superior to the other clusters with respect to the desirable characters. The genotypes were ranked based on the selection indices. High yielding and superior genotypes had high selection indices while low yielding genotypes were having low selection indices. Field screening of 49 genotypes for leaf curl virus resistance (experiment II) showed that five genotypes were highly tolerant to the disease while 14 genotypes were susceptible and 30 were highly susceptible. Comparison of yield and vulnerability index in both the experiments showed that reduction in yield was less in tolerant varieties than in susceptible varieties. The yield performance of Karumukku local, Thavanur local 3 and Meenachil local were comparable under controlled and uncontrolled conditions. Correlation analysis showed negative association of yield with vulnerability index in both experiments indicating that susceptibility to the disease leads to reduction in yield. The high yielding and leaf curl tolerant types identified from the study can be used as parents in crop improvement programme to evolve high yielding, leaf curl tolerant varieties. RAPD analysis was performed using the random primers OPA-01, OPB-01, OPB-06 and OPB-10 and the 49 genotypes were characterized using Jaccard’s similarity coefficient analysis and a dendrogram was constructed to cluster the genotypes. The high yielding genotypes T1 (Karumukku local) and T15 (Thavanur local 3) came in the same cluster (cluster II) while the leaf curl virus tolerant genotypes T35 (Kayamkulam local 3) and T33 (Kayamkulam local 4) came in the other cluster (Cluster I).