Identification of drought-tolerant maize (Zea mays L.) hybrids using yield components and drought tolerance indices

Recurrent and prolonged droughts during the maize-growing season in Southern Africa severely threaten food security due to significant yield losses, especially during the flowering stage. Conventional breeding has identified key secondary traits and indices to aid in selecting drought-tolerant genotypes. This study was conducted to evaluate the performance of newly developed maize hybrids under drought stress to identify climate-resilient cultivars for vulnerable regions. The yield and yield components were used to screen nine maize (Zea mays L.) hybrids for tolerance to drought stress at the flowering stage under field conditions. Nine hybrids and a drought-tolerant check (ZM525) were arranged in a 2 × 5 Randomised Complete Block Design with three replicates under well-watered and drought-stressed conditions. Data on days to 50% silking (DS) and anthesis (DA), anthesis-silking interval (ASI), ears per plant (EPP), number of rows per ear (NRE), cob length (CL) and grain yield (GY) were recorded. The hybrids differed significantly (p less than 0.01) for ASI, EPP, EL and GY. Highly significant differences (p less than 0.05) in hybrid by environment interaction were observed for ASI and grain yield only. Based on the results, drought stress significantly widened ASI (-5.7 to 5.3 days) and reduced GY by approximately 50%. Five drought tolerance indices (TOL, SSI, STI, MP, GMP) were used for screening and H6 and H1 outperformed the check (ZM5230) and other hybrids under stress. On the other hand, H5 and H7 exhibited great stability across environments. The principal component analysis showed a strong correlation among DS, DA, GY and all indices except TOL. Based on recorded traits and indices, H6 and H1 exhibited tolerance, while H3 showed great susceptibility to drought stress.