Identification of wheat genotypes tolerant to the effects of heat stress on grain quality.
Blumenthal C. | Bekes F. | Gras P.W. | Barlow E.W.R. | Wrigley C.W.
High-temperature stress (> 35 degrees C) during the grain-filling period has the potential to modify grain quality. A consequent weakening of dough properties has been reported for many wheat genotypes. The experiment described in this article was designed to identify wheat genotypes that might be tolerant to the effects of heat stress on grain quality and to further assess the molecular basis of these changes. A diverse set of 45 wheat genotypes was exposed to 10 hr of 40 degrees C on each of three consecutive days in a phytotron. Mean values for all genotypes (with unheated control samples, all in duplicate) showed highly significant changes (P < 0.001) in 1,000 kernel weight (-17% difference for heat stressed minus control), protein content (17% increase), dough mixing time in a 2-g Mixograph (-13%), and resistance breakdown (17%). The general weakening of dough due to heat was accompanied by a decrease in glutenin-to-gliadin ratio and in the percentage of very large glutenin polymers. Bound lipid content increased, and there was a general reduction (-9%) in the proportion of small (B-type) starch granules. For all these attributes, reactions for individual genotypes ranged from little change (tolerance to heat stress) to considerable change (susceptible to heat stress). A group of genotypes was thus identified that should be useful in breeding attempts to stabilize wheats against heat-related variations in grain quality. Markers identified as potentially useful in breeding for tolerance include the presence of the Glu-D1d allele (glutenin subunits 5 and 10), and increases in glutenin-to-gliadin ratio and in the percentage of very large glutenin polymers.
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