PHENOTYPIC DIVERGENCE OF RICE (ORYZA SATIVA L.) GENOTYPES UNDER FARMERS FIELD AND COASTAL SALINE FIELD CONDITION

Genetic divergence is a pre-requisite for the production of superior recombinants for the crop improvement program. The nature and magnitude of genetic divergence were estimated in 33 genotypes of rice for ten quantitative characters under normal environment (E1) and saline field environment (E2) were considered and evaluated using D 2 statistics from Mahalanobis. The analysis of variance revealed a highly significant difference among the rice genotypes for all the ten traits studied. All the genotypes show significant variations in their mean output for all the ten characters examined. Based on the study of Mahalanobis D 33 genotypes were grouped into 6 clusters in E1 and nine clusters in E2 and eleven clusters in the pooled analysis. The clustering pattern showed that there is little parallelism exists between geographical origin and genetic diversity, because genotypes from different geographical to source fall within the same cluster and vice versa. The intracluster distance ranged from 449.47 in cluster II to a maximum distance of 7829.81 in cluster IV and the inter-cluster distance D values also varied widely between cluster I and IV with a maximum value of 7349.49 and a minimum value of 993.80 between cluster II and cluster III under E1. In E2 intracluster distance ranged from 279.84 in cluster II to 6149.94 cluster VIII and minimum inter-cluster distance showed between cluster VII and VIII (4768.74) and the minimum was recorded between cluster III and cluster VII (515.65). Among ten characters studied Days to 50 per cent flowering (22.16), 100 seed weight (22.16), number of tillers per plant (18.75), and grain yield per plant (10.04) are the four major contributing traits towards genetic divergence in E1; in E2 three characters days to 50 per cent flowering (11.74), 100 seed weight (26.52) and grain yield per plant (27.08) and in pooled analysis days to 50 per cent flowering (21.40), plant height (11.36), number of tillers per plant (21.40) and grain yield per plant (17.80) are the four major contributors. Comparison of mean of various characters over normal (E1) and saline field environment (E2) revealed the phenomena of decreased plant height along with the reduced number of tillers per plant, number of panicles per plant, flag leaf length, flag leaf breadth, panicle length, number of grains per panicle and grain yield per plant under saline field environment (E2). When compared to normal crop growth in (E1). Grain yield was drastically affected by an increase in salinity. In our investigation, three genotypes G7, G20, G15 which recorded stable and high yield under salinity. Therefore, selection of divergent genotypes from the clusters namely III and IV, II and VIII and II and X from E1, E2 and pooled analysis respectively would produce a broad spectrum of variability for different traits studied, which may enable further selection and improvement of grain yield along with saline tolerance. The hybrids developed from the genotypes (AURC 2108, AURC 2204, AURC 2117) within the limit of compatibility of these clusters may produce the high magnitude of heterosis or desirable segregants which would be rewarding in a rice breeding programme.