Sunny, K OmmenDeepthi, SivanandanKAU2019-05-312019-05-312003172202http://krishikosh.egranth.ac.in/handle/1/5810106084PGOkra is an important vegetable crop grown in India and abroad for its fresh green pods. The leafhopper Amrasca biguttula biguttula is a major sucking pest of okra causing high damage to plants. High frequency of fruit picking and repeated application of chemical pesticides to tackle the hopper menace, often leaves toxic residues in the fruits. So it is inevitable that pest resistant varieties should be developed. Hence a study was undertaken to study the genetic variability, for yield and its component characters as well leafhopper resistance indices in a collection of okra genotypes, to estimate the combining ability and heterosis as well as gene effects involved in the inheritance of these characters using line x tester analysis. Forty okra germplasms collected from vanous sources were evaluated simultaneously for yield and leaf hopper resistance. ANOV A revealed that the treatments varied significantly for leafhopper resistance and also there was significant variation among treatments for yield and yield attributes viz., days to first flowering, leaf axil bearing first flower, number of primary branches, number of fruits per plant, length of fruit, girth of fruit, weight of fruit, yield per plant duration. Six genotypes exhibited resistance to the leafhopper throughout the crop duration. High values for phenotypic and genotypic coefficients of variation was recorded for number of primary branches followed by leafhopper population count. High heritability was exhibited by yield per plant followed by duration. Maximum genetic advance was observed for number of primary branches followed by yield per plant. Correlation analysis indicated that most character combinations had higher genotypic correlation coefficient than phenotypic correlation coefficient. Yield exhibited significant and positive correlation with number of fruits and average fruit weight and negative significant association with leaf axil bearing first flower, leafhopper population count and leafhopper injury score. Path analysis was carried out for nine biometric as well as two leafhopper injury indices which had high correlation with yield. Highest positive direct effect was exhibited by number of fruits while the highest negative direct effect on yield was recorded for leafhopper population count per plant. Resistant as well as susceptible genotypes were selected based on leafhopper population counts and leafhopper injury score. Five resistant lines (female parent) viz., Nemom (T21), re 45792, Venjaramood (T23), AE 279 and Palappur (T20) and three susceptible testers (male parent) viz., Venganoor (T1S), Aruna (T37) and Kalliyur (T24) were selected as parents for L x T analysis. These were crossed in a line x tester fashion to produce 15 hybrids. During L x T programme highly significant sea as well as gea effects were obtained for yield. Lt was the best line while T 2 was the best tester. Among hybrids L3 x T 2 was the best considering leafhopper resistance as well as yield and yield attributes. Negative and significant sea effects were observed for days to first flowering and leafhopper population count. It possessed all the desirable characters like high yield, greater weight and girth of fruits and number of fruits. It is also an early flowering type. The ratio of additive to dominance variance was less than one for most of the traits studied including leafhopper population counts and leafhopper injury , scores, indicates the predominance of non-additive gene action. Since there is preponderance of non additive gene effects for characters such as yield and its components as well as leafhopper resistance parameters, exploitation of hybrid vigour is an appropriate breeding approach where yield and leafhopper resistance are considered.ennullThesis