Influence of Heat Stress on Wheat Grain Characteristics and Protein Molecular Weight Distribution

Abstract

Wheat (Triticum aestivum L.) plants exposed to high temperatures (>35 C) during ripening show altered agronomic and grain quality characteristics. Seasonal variation in quality creates difficulties in the marketing and processing of grain. Improving the genetic adaptation of wheat cultivars to heat stress is an important objective in breeding programs. Some genotypes have been reported to have a thermo tolerant response and could be used as genetic sources for heat tolerance. Fourteen spring wheat genotypes (Debeira, Estanzuela Cardenal, Estanzuela Pelón 90, INIA Boyero, INIA Caburé, INIA Churrinche, INIA Cóndor, INIA Mirlo, Pavón 76, Trigo 3, Ventnor, LE 2262, LE 2265, LE 2290) were evaluated in INIA La Estanzuela, Uruguay, to characterize their response to high temperatures. Variation in the duration and timing of heat stress was assessed in two greenhouse experiments. Grain protein concentration increased with heat stress, having the greatest effect when stress was imposed early in grain fill. High temperatures reduced the length of the grain fill period. A longer duration of heat stress resulted in the shortest grain fill period, but there was no difference in grain fill duration with respect to timing of the stress. Heat stress reduced thousand kernel weights without any effect attributable to the duration or timing of stress. Heat stress did not noticeably influence the protein quality of a selected subset of six wheat genotypes, measured using high-performance liquid chromatography (HPLC). However, significant genotype x treatment interaction was detected. INIA Churrinche showed a decrease in the ratio of polymeric to monomeric gluten proteins in response to heat stress. For Estanzuela Pelón 90, INIA Cóndor, and Trigo 3, the ratio was unchanged, and for Debeira and Pavón 76, the ratio increased. Cultivars with relatively stable grain characteristics and protein molecular weight distribution were identified and could be used as genetic sources for improving resistance to heat stress