Genetic Variation for Tolerance to Terminal Heat Stress in

Heat stress substantially reduces the grain yield and quality of wheat (Triticum aestivum L.,2n = 6x = 42, AABBDD genome) and poses a major challenge to sustaining productivity because of global warming. Across wheat-growing regions in the United States and globally, wheat often experiences terminal heat stress during the postflowering period. Dasypyrum villosum, a wild relative of wheat, has been a useful genetic resource for the improvement of several traits in wheat. Here we report a first survey of terminal heat tolerance in D. villosum. Twenty accessions of D. villosum from seven countries and three common wheat cultivars (checks) were compared. Agronomic traits including single kernel weight, total grain weight, grain number, and shoot weight were evaluated in both nonstress(22 degrees C day, 17 degrees C night) and heat stress (36 degrees C day, 30 degrees C night) conditions in two independent experiments. The results showed that there was significant genetic variation for heat tolerance during the grain-filling period in D. villosum and that single kernel weight was less affected by heat stress in D. villosum than in common wheat. Three accessions, TA10228 and TA10225 originating in Italy and TA2172 in Turkey, showed the highest terminal heat tolerance. This work suggests that D. villosum may be a useful novel resource for the improvement of heat tolerance in common wheat.