Abstract

An experimental trial on eight rice genotypes was designed at the field of Institute of Agriculture and Animal Science, Lamjung, Nepal under randomized complete block design with three replications from June-November 2017 to study the nature and extent of correlation among yield and yield attributing characters under reproductive heat stress. Grain yield was significantly correlated with 1000-grain weight (r=0.838**), SPAD reading (0.815*), relative water content (0.803*), harvest index (0.771**) and number of filled grains per panicle (0.719*) suggesting an instrumental role of these traits as “selection criteria” for yield improvement. The grain yield had negative non-significant association with the number of non-effective tillers per m2 (−1.05), sterility % (−0.378) and panicle length (−0.52). While the positive non-significant association with grain yield was exhibited by flag leaf area (0.161), the number of effective tillers per m2 (0.173), number of tillers per hill (0.634), plant height (0.110) and days to 50% anthesis (0.63*). The path coefficient analysis of different traits revealed highest positive direct effect of the number of tillers per hill (0.7220) followed by days to 50% flowering, SPAD reading, number of filled grains per panicle, 1000-grain weight, panicle length and harvest index upon yield. However, relative water content, sterility %, the number of effective, non-effective tillers per m2 and plant height expressed negative direct effect upon grain yield. Relative water content (pivotal drought parameter) had negative direct effect upon yield but its residual positive effect was justified via other traits such as tiller number, SPAD reading, days to 50% flowering and number of filled grains per panicle.