Identification of heat tolerant hybrids based on morphological traits and selection indices

Development of climate resilient cultivars is necessary for maize production as increased temperature have negative impact on maize yield. Selection based on grain yield along with stress-adaptive secondary traits could help in the development of improved, stable heat stress tolerant cultivars. The current study was conducted to identify reliable and effective secondary traits associated with heat stress tolerance in tropical maize. A Six hundred and sixty two double haploid lines derived from nine bi-parental pedigree populations were phenotyped under natural heat stress and optimal condition. Evaluation was carried out under optimal and natural heat stress condition by sowing on 1st week of February and March to expose the reproductive stages and grain filling period during heat stress. Various morphological traits under study were significantly affected by heat stress. ASI found negative correlation and direct effect while EH observed positive correlation and direct effect under heat stress condition. In both conditions, grain yield found positive and significant correlation with STI, MP and GMP as indicated the better heat stress tolerant indices toward Yp and Ys. Results of this study showed that the DH line, DH_1_178 identified as heat tolerant line since this DH line had high grain yield in both conditions and this line can used in future heat tolerant breeding programme.