Heat stress due to prolonged high ambient temperature during critical growth stages is a serious threat to crop production worldwide. Though being a C4 crop, maize has relatively wider adaptation, however, weather extremes such as heat stress is challenging its threshold limits. There is an absolute requirement of heat tolerant cultivars in the present condition as climate change has a become reality. This study was designed to assess the genetic gain in various stress-adaptive traits of maize testcrosses derived from two heat tolerant heterotic multi-parental synthetic (MPS 1 and MPS 2) populations. The trial consisted of 405 F2:3 testcrosses derived from MPS 1 along with two commercial checks and 470 F2:3 testcrosses derived from MPS 2 along with five commercial checks. They were evaluated in Alpha lattice design with two replications at Main Agriculture Research Station, Raichur, Karnataka during spring season where the most part of reproductive stage, starting from tassel emergence until late grain filling, was exposed to heat stress. Analysis of variance revealed that the mean sum of squares due to genotypes in MPS 1 differed significantly for grain yield and MPS 2 showed significant variation among genotypes for all the characters studied, indicating the presence of variability for all the traits in the germplasm utilized for present study. The top 10 per cent of the F2:3 families of MPS 1 and MPS 2 populations were selected based on their testcross performance and subjected to genetic gain study. The maximum genetic gain was observed for grain yield (), days to 50 per cent anthesis (), days to 50 per cent silking (), ASI (), plant height () and ear height () in MPS 1 population compared to MPS 2 population. | Genetic gain in Testcrosses derived from heat tolerant multi-parental synthetic populations of maize
