Abstract
Rice stem borer (Chilo agamemnonBles.) is a primary insect pest of rice and is a major limiting factor to riceproduction. Breeding for insect-resistant crop varieties has been an economic way of integrated pest management(IPM) as it offers a viable and ecologically acceptable approach. This study was aimed to evaluate rice genotypesfor their resistance against rice stem borer. Seven parental genotypes with twenty one F1crosses were evaluatedfor genotypic variation infield experiments. Analysis of variance revealed significant differences for the studiedtraits in almost all crosses and parents. In addition, the mean squares of parentsversustheir crosses were signifi-cant for stem borer resistance and other associated traits. Moreover, both general combining ability (GCA) andspecific combining ability (SCA) variances were highly significant for all characters studied in the F1generation.Based on GCA, 4 genotypes (Sakha101, Gz6903-3-4-2-1, Gz9577-4-1-1 and Hassawi) exhibited highly significantnegative values for stem borer resistance (-0.53,-1.06,-0.18 and-0.49, respectively) indicating they are the bestcombiners for stem borer resistance. Based on SCA analysis, nine cross combinations showed highly significantnegative effects for stem borer resistance. Similarly, the cross Giza178 Hassawi was the best combination withsignificantly highest value for early maturity. In addition, seven crosses showed highly significant negativeSCA for plant height trait. On the other hand, for panicle length, number of primary branches/panicle, panicleweight and 1000-grain weight, seven, four, eight and six crosses showed highly significant positive SCA, respec-tively. The result further revealed that the non-additive dominance genetic variance was higher than the additivevariance for all evaluated traits indicating that non-additive genetic variances have a role in their inheritance. Thebroad-sense heritability estimates were high for all the studied traits. The stem borer resistance was significantlycorrelated with panicle weight and 1000-grain weight, which also showed a highly significant correlation withgrain yield/plant. Thus these traits can be effectively employed in a breeding program to confer resistance againststem borer infestation in rice. It was further supported by biplot analysis, which clustered these potentially impor-tant traits into two quadrants showing their importance in any future breeding program to control stem borerinfestation. This study has contributed valuable information for evaluation of genetic diversity in the local ricegermplasm and its utilization in futuristic rice genetic improvement programs.