Heterosis for Yield Component Traits and Protein Content in Bread Wheat under Normal and Heat-stress Environment

A study was conducted during 2008-2010, to estimate heterosis for yield component traits and protein content in bread wheat under normal and heat-stress environment by utilizing a set of 45 half diallel cross combinations, involving 10 diverse parents. Analysis of variance revealed significant differences for the two environements, whereas differences over the years were non-significant for all the traits. The pooled data over the years, exhibited highly significant differences for all the traits under both normal and heat-stress environments. The number of tillers/plant exhibited maximum degree of standard heterosis under normal and heat-stress environment (with value of 12.62% and 53.75%), respectively. In general, spike length (16.02%) and number of grains/spike (52.10%), showed higher magnitude of standard heterosis under normal environment than heat-stress environment, whereas number of tillers/plant (53.75%) and gain filling duration (43.68%) showed higher standard heterosis in heat-stress environment than the normal one. For grain yield/plant, 1000-grain weight and protein content, the number of cross combination showing standard heterosis were almost same in both the environments. The ten crosses, out of forty-five crosses, namely HD 2733/WH 542; PBW 343/UP 2425; HD 2687/PBW 343; PBW 343/UP 2382; PBW 343/HD 2285; WH 542/UP 2425; PBW 343/PBW 226; UP 2382/HUW 468; PBW 343/WH 542 and PBW 226/HD 2285 can be used to select transgressive segregants for normal as well warmer wheat growing areas. These ten combinations can be used by involving, the trait grain filling duration, tillers per plant, spike length, grains per spike, 1000-grain weight to improve grain yield for warmer areas. In all 45 cross combinations, six cross combinations were identified for better per se performance for grain yield as well as protein content under heat-stress environment. These combinations may thus be used for developing superior genotypes through fixation of heterosis are also supported by high SCA. Besides, results of present study also revealed ample scope for developing transgressive segregants involving some of these parents to develop high yielding genotypes in wheat suitable for heat stress environments.