Submitted to: Journal of Agronomy and Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/4/2005
Publication Date: 1/1/2006
Citation: Tewolde, H., Fernandez, C.J., Erickson, C.A. 2006. Wheat cultivars adapted to post-heading high temperature stress. Journal of Agronomy and Crop Science. 192:111-120. Interpretive Summary: Exposure of wheat to temperatures that exceed about 60oF after it forms flowers is known to detrimentally affect its grain production and milling quality. Wheat in the USA, particularly in the southern regions, often experiences temperatures that exceed 85oF implying substantial loss of grain production. Despite knowledge of the existence of genetic tolerance to high temperature, not much is known about the heat tolerance characteristics of wheat varieties that come to production. We evaluated 15 wheat varieties and one experimental line for their heat adaptation at the Texas A&M University Agricultural Research and Extension Center at Uvalde, Texas. The results show that early flowering may be the most effective single trait defining wheat varieties adapted to production systems prone to high temperature stress during grain maturation. Early flowering allows wheat to complete all or a greater fraction of its grain maturation period during favorable temperatures and avoid late-season rise of temperature. Varieties with this trait plus a reasonable grain growth rate should potentially be the varieties of choice for production in regions characterized by rapid temperature rise late in the wheat growing season. Such varieties should also be chosen for late planting or other situations where the wheat crop may mature during periods of high temperatures. Based on their earliness to flowering and grain production, we identified the varieties Collin, TAM 201, TAM 202, MIT, and Coker 9835 and the experimental line TX87U7003 to be well-adapted for southwestern Texas and similar other wheat production regions.
Technical Abstract: The existence of genetic variation in wheat (Triticum aestivum L.) for tolerance to high temperature stress has been reported, but cultivars released for a particular production system often are not characterized. The objective of this study was to identify and describe the characteristics of wheat cultivars adapted to production systems with risks of high temperature and drought during the reproductive stages of growth. Fifteen diverse wheat cultivars and one unreleased genotype were evaluated at the Texas A&M University Agricultural Research and Extension Center, Uvalde, TX during two seasons characterized by daily maximum temperatures as high as 36oC. Measurements during both seasons included days to heading, days to physiological maturity, and grain yield. Large and significant (P<0.05) grain yield differences were measured among cultivars within each season. Yield varied between 2979 and 4671 kg/ha in the first season and between 1916 and 5200 kg/ha in the second season. Late planting in the second season delayed heading date resulting in grain filling to coincide with periods of high temperatures. Within each season, early-heading cultivars outperformed late-heading cultivars because of two distinct advantages. The early-heading cultivars had longer grain filling period than the later-heading cultivars. In addition, early-heading cultivars completed a greater fraction of the grain filling when air temperatures were lower and generally more favorable. The results suggest that early-heading may be the most effective single characteristics defining wheat cultivars adapted to production systems prone to high temperature stress during grain filling.