Deciphering variability for heat tolerance index in maize hybrids and identification of stress resilient heterotic combinations

Abstract

Aim: High temperature at any critical stage for a prolonged duration is documented to negatively affect the growth and yield related processes in maize. Therefore, the present study was planned to identify resilience of different heterotic combinations to heat stress under field conditions. Methodology: A set of 20 parental lines were used as parents and 21 single cross hybrids raised in kharif 2020 using 16 lines as female parent and four lines as male parent along with three commercial checks using randomized block design under two regimes: Normal Sownin mid of February, i.e., timely sown condition (spring season crop) and late sown in mid of March (heat stress crop). Data was recorded for yield and its contributing traits. Results: Heat stress led to early onset of flowering, thus resulting in shortening of vegetative phase. Consequently, days to grain filling period was found to be reduced (84-106 days) under late sown as compared to 100-123 days under normal sown condition. Amongst the top performing six hybrids in both normal sown and late sown conditions, three hybrids were common viz., JH 20003, JH 20015 and JH 20018, though with different ranking, inferring their wider adaptability and tolerance to heat stress. Under late sown conditions, days to grain filling (r2=0.55) and thousand seed weight (r2 =0.50) showed significantly positive correlation with grain yield while as highly significant and negative association was observed between anthesis silking interval and grain yield (r2 = -0.76). Among the 21 hybrids, three hybrids (JH 20001, JH 20004, and JH 20015) showed greater potential under heat stress conditions on the basis of yield performance under stress, percent yield reduction and heat tolerance index. Interpretation: Based on multiple selection criteria, three hybrids viz., JH 20001, JH 20004, and JH 20015 were suggested for commercial utilization after validation. This study also led to identification of donor inbreds which can contribute to breeding for heat stress tolerance. Key words: Grain yield, Heat tolerance index, Heat stress, Maize, Percent yield reduction