VISWANATHA, K. P.Maruthi, J.2017-07-132017-07-132008-08-10Th-9153http://krishikosh.egranth.ac.in/handle/1/5810025159An investigation was undertaken to estimate the nature and extent of the genetic variability, divergence among the 169 cowpea genotypes. Association of various characters with yield and its attributing characters were also studied. Diversity at molecular level was estimated using SSR markers and the molecular diversity was compared with morphological diversity. The analysis of variance revealed significant differences for all the ten characters including yield. The estimates of PCV and GCV were high for all the characters except days to physiological maturity and plant height. Positive and significant correlations of seed yield with plant height, number of branches, clusters, pods per plant, number of seeds per pod and test weight was observed. Rath analysis indicated that the traits number of pods per plant and test weight had high direct effects on seed yield. Genetic divergence study using Mahalanobis D2 statistic grouped 169 genotypes into eight clusters. Maximum genotypes were grouped in the cluster VI (5 I genotypes). Maximum contribution towards total divergence was by Seed yield per plant. The genotypes were also screened against three major diseases viz. mosaic virus, rust and leaf spot under natural conditions. Thirty lines were found resistant to all the three diseases in the field condition. The genotypes TC99-1, EC170584-1-1, NBC43, ^ P58. V240 and IC202711(58) were found superior to checks and were showing high yield as well as multiple disease resistance under natural field condition. Fifty representative genotypes were selected for molecular characterization. The results revealed 45 to 100 per cent similarity between the lines at molecular level. Clustering of the morphological data was carried out using correlation coefficient. The genotypes exhibited 88 to 100 p e rc e n t similarity at morphological level. The study revealed that diversity at molecular level was very high compared to diversity at morphological level, suggesting higher resolution for diversity from molecular data than morphological dataennullThesis