Grain and flour quality of wheat genotypes grown under heat stress

Heat stress during the grain-filling period is the main abiotic stress factor limiting grain yield and quality
in wheat (Triticum aestivum L.). In this study, 64 wheat genotypes were exposed to heat stress during
reproduction caused by delayed sowing in two growing seasons. Grain yield, 1000 grain weight (GW),
grain hardness (GH), and grain-quality related traits were investigated. Heat stress caused a significant
decrease in GW through reducing starch content (SC) and a non-compensating rise in protein content
(PC), and thereby resulted in lower yield. In addition, significant increases in flour water absorption
(WA), Zeleny sedimentation volume (ZT), ash content (AC), lipid content (LC), loaf volume (LV), wet gluten
content (WG), dry gluten content (DG), gluten index (GI), and amylopectin content (APC) were found
following heat stress. In contrast, decreases in grain moisture content (MC) and amylose content (AMC)
induced by heat stress were observed. The heat-tolerant genotypes were superior in grain yield, GW, SC,
AMC, and MC. While the sensitive genotypes contained higher PC, LV, GI and AMP. A group of wheat
genotypes characterized with a higher yield, AMC, GW, and SC as well as lower PC, WA, GH, ZT, and
LV; and was found to be the most heat tolerant by principal component analysis. Lighter weight and
smaller grains produce a smaller starchy endosperm with lower quality (less amylose) and higher grain
protein content in heat stress compared to normal conditions. Heat stress caused by delayed sowing
improves some of the baking-quality related traits