Heat Stress in Wheat during Reproductive and Grain-Filling Phases

TLDR

Rising global temperatures threaten wheat production by inducing heat stress during reproductive and grain‑filling stages, which impairs photosynthesis, causes oxidative damage, and reduces grain yield, though heat‑shock protein–expressing genotypes show greater resilience. The review aims to evaluate how heat stress during key developmental stages affects grain yield and to propose breeding strategies to enhance wheat heat tolerance. It proposes that breeding for heat tolerance should target secondary traits such as membrane stability, photosynthetic rate, grain weight, and grain‑filling rate, integrating physiological, biotechnological, and conventional methods to improve yield under heat stress.

Abstract

Ambient temperatures have increased since the beginning of the century and are predicted to continue rising under climate change. Such increases in temperature can cause heat stress: a severe threat to wheat production in many countries, particularly when it occurs during reproductive and grain-filling phases. Heat stress reduces plant photosynthetic capacity through metabolic limitations and oxidative damage to chloroplasts, with concomitant reductions in dry matter accumulation and grain yield. Genotypes expressing heat shock proteins are better able to withstand heat stress as they protect proteins from heat-induced damage. Heat tolerance can be improved by selecting and developing wheat genotypes with heat resistance. Wheat pre-breeding and breeding may be based on secondary traits like membrane stability, photosynthetic rate and grain weight under heat stress. Nonetheless, improvement in grain yield under heat stress implies selecting genotypes for grain size and rate of grain filling. Integrating physiological and biotechnological tools with conventional breeding techniques will help to develop wheat varieties with better grain yield under heat stress during reproductive and grain-filling phases. This review discusses the impact of heat stress during reproductive and grain-filling stages of wheat on grain yield and suggests strategies to improve heat stress tolerance in wheat.