Grain yield, its components and some physiologic characteristics of flag leaf in commercial wheat cultivars in response to post-anthesis drought stress

Introduction: Wheat ranks first among crops regarding cultivated area and production worldwide and in Iran. Drought stress is the most common abiotic stress that decreases the grain yield of crops. Physiologic characteristics with some traits related to grain yield and its components are used as indices to evaluate wheat cultivars under drought stress conditions. This experiment aimed to study the grain yield components and some physiologic characteristics of the flag leaf and their relationship with grain yield in commercial wheat varieties under post-anthesis drought stress conditions. Materials and methods: This experiment was conducted at Razi University. The experiment was arranged as a split plot basis on a randomized complete block design with three replications. Two moisture treatments (no stress and post-anthesis drought stress) were placed in the main plots and 14 wheat cultivars were considered in the sub-plots. Traits related to grain yield (including biologic, grain and straw yields and harvest index), grain yield components (including number of spikes per square meter, number of grains per spike and 1000-grains weight) and some physiologic characteristics of flag leaf (including flag leaf area, chlorophyll a, chlorophyll b, total chlorophyll, chlorophyll a/b ratio and proline content) were measured. Results: The effect of drought stress on biological yield, grain yield, harvest index, number of grains per spike, 1000-grain weight, flag leaf area, chlorophyll a/b ratio and flag leaf proline content was significant, but on straw yield, number of spikes per square meter, chlorophyll a, chlorophyll b, and total chlorophyll was not significant. Wheat cultivars significantly differed in the mentioned characteristics (except for chlorophyll a, chlorophyll b and total chlorophyll). The damage of post-anthesis drought stress on the grain yield reduction was more than straw yield (41 vs. 9% reduction). Among the grain yield components, 1000-grain weight had greater damage than the number of grains per spike (35 vs. 11% reduction) in response to drought stress. Drought stress decreased the amount of chlorophyll but increased the chlorophyll a/b ratio and proline content of the flag leaf. Correlation analysis showed that under normal moisture conditions, harvest index and chlorophyll content in flag leaf had the highest positive correlation with grain yield. While, under post-anthesis drought stress conditions, the highest positive correlation belonged to the proline content of flag leaf and 1000-grain weight. Conclusion: Some physiologic characteristics of flag leaf (such as proline) with grain yield components (such as 1000-grain weight) could be used to evaluate wheat cultivars under post-anthesis drought stress conditions.Keywords: 1000-grain weight, flag leaf area, harvest index, proline.