Dissection of heat tolerance mechanism in tropical maize

Identification of diverse inbred lines and selection of heat tolerant genotypes based on key secondary traits that influence the grain yield is of great importance. In the present study, correlation coefficient and path analysis were used to identify potential traits for heat tolerance. The results on correlation studies revealed that grain yield per plant had positive relationship with number of kernels per cob (0.833), shelling percentage (0.592), chlorophyll content (0.575), plant height, ear height, 100-seed weight, pollen shed duration and cob length. The traits like days to 50% tasseling (−0.383), days to 50% silking (−0.382), anthesis silk interval (−0.381), senescence and cell injury (%) were negatively associated with grain yield. Further, path analysis showed that the number of kernels per cob had highest positive direct (0.6689) and indirect effect via chlorophyll content and days to 50% tasseling on grain yield followed by shelling percentage through number of kernels per cob, days to 50% tasseling and chlorophyll content. Cluster analysis based on phenotypic data showed presence of three main groups. The first group (GI) consisted of four inbred lines (5.1%) which were superior to mean of 75 inbred lines in respect of all the traits. The selection of genotypes based on number of kernels per cob, anthesis silk interval, shelling percentage, chlorophyll content, plant height and ear height will indirectly increase the maize yield under heat stress.