Effects of kernel weight and source-limitation on wheat grain yield under heat stress

Abstract

High temperature in terminal growth stages is a major stress of wheat productivity in South-west Iran, as well as in other Mediterranean environments and the long-term spring temperatures trend to increase. Determination of affecting factors or traits helps to improve the yield potential of wheat. The effects of heat stress during and post anthesis for physiologic, phenologic and agronomic traits was evaluated in ten bread wheat genotypes. The research was conducted under field condition in two different dates under less and more heated environments (two different sowing times). Also, source levels were manipulated through 50% spikelet removal at anthesis to evaluate cultivar source/sink limitations to kernel growth. The results depicted that grain yield, kernel number per spike and 1000 kernel weight were reduced by 24.1%, 9.2% and 23.7% in warmer environment, respectively. Hence, kernel weight was more suited for heat stress screening than other traits evaluated in this study. Thus, wheat genotypes that are able to maintain high individual kernel weight despite heat stress may possess a high level of heat tolerance. Furthermore, results indicated that the poor grain filling could mainly be attributed not to sink-limited conditions, but to source-limited conditions.

Key words: Heat, stress intensity, tolerance, sink-source limitation.