| Summary: | Low rainfall combined with heat stress during grain filling can cause a severe threat to maize production. Compared to individual stress, the impact of combined stressors on plant performance during the grain filling remains less explored. In this study, two maize genotypes, ‘B73’ and ‘Mo17’, were subjected to four treatments (control, drought stress, heat stress, and combined drought and heat stress) to understand how maize genotypes respond to stressors during grain filling. Stomatal conductance displayed an opposite response between drought and heat or combined stresses during the mid-grain filling stage. Averaged over genotypes, decreased stomatal conductance (67.4%) and increased leaf temperature (5.6 °C) under combined stress treatments resulted in a significant yield reduction (78.9%) compared to control. Drought or combined stressors during the grain filling stage had a predominant effect on sink potential (kernel weight) than heat stress. Reduction in kernel size of genotype ‘B73’ was associated with a 5.5% decline in starch under heat stress. Analysis of individual and interactive stressors effects on maize showed that trait responses could vary with stresses during grain filling. The present study showed that the maize phenotypic responses differ between individual and interactive stresses. The genotype ‘Mo17’ exhibited relatively higher tolerance to both individual and combined drought and heat stresses than ‘B73’. The present study highlighted the maize plant responses to individual and combined stresses, which is essential for improving maize tolerance to drought and heat stress conditions.
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