Evaluation of heat stress tolerance indices in maize inbred lines

The heat stress during flowering, pollination and grain filling stages affect the productivity of maize. Twenty maize inbred lines were evaluated in field and plastic houses using alpha lattice design with two replications during spring season of 2016 at National Maize Research Program, Rampur, Chitwan, Nepal. Five stress tolerance indices namely stress susceptibility index (SSI), stress tolerance index (STI), tolerance index (TOL), geometric mean productivity (GMP) and mean productivity (MP) were applied to identify superior heat stress tolerant lines. The results showed that STI, SSI, GMP and MP indices were the more accurate criteria for selection of heat tolerant and high yielding lines. The positive and significant correlation of GMP and MP with grain yield under both conditions revealed that these two indices were more applicable and efficient for selection of inbred lines. The biplot analysis identified the groups of tolerant and sensitive inbred lines. The maize inbred lines namely RL-140 and RML-91 found high yielding and low stress susceptibility in both conditions. These results suggest that the inbred lines namely RL-140 and RML-91 should be use a source of heat tolerance for maize breeding program