VIEW ARTICLE

Resistance

High-Temperature, Adult-Plant Resistance to Stripe Rust of Wheat. A. Qayoum, Research associate, Department of Plant Pathology, Washington State University, Pullman, WA 99164; R. F. Line, plant pathologist, Agricultural Research Service, U. S. Department of Agriculture, Pullman, WA 99164. Phytopathology 75:1121-1125. Accepted for publication 10 May 1985. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1985. DOI: 10.1094/Phyto-75-1121.

Resistance to Puccinia striiformis in plants of winter wheat cultivars at different growth stages was studied in the greenhouse at low diurnal temperatures (2- 18 C, 4- 18 C, and 6- 21 C), high diurnal temperatures (13- 32 C, 13- 34 C, and 15- 36 C), and under natural conditions in the field. The cultivars were susceptible in the seedling stage at both low and high temperatures and at all stages of growth at low temperatures. At the high temperatures, cultivars Cheyenne, McCall, Gaines, Itana/PI 178383 Selection 111, Wanser, Nugaines, and Luke at the boot and later growth stages showed resistance that increased as the plants matured; cultivars Michigan Amber, Orin, Omar, Golden, Columbia, Westmont, Itana, and Itana/PI 178383 Selection 110 were susceptible at all growth stages. Cultivars that were resistant at the high temperatures differed in degree of resistance, and cultivars that had the highest resistance at later stages also expressed resistance earlier than those with less resistance at later stages. High-temperature adult-plant resistance was expressed only at the high postinoculation temperatures. Flag leaves were more resistant than the lower leaves of the same plant. Cultivars that were resistant at the high postinoculation temperature became susceptible when subsequently transferred to a lower temperature. The results were similar for all races tested; there was no evidence of race-specificity. The cultivars with high-temperature adult-plant resistance were resistant in the field at the jointing and later stages of growth, and rust developed slower on them. This type of resistance has been used extensively in wheat breeding programs and has remained effective against all races of P. striiformis in the northwestern United States for more than 20 yr indicating that it is durable and may be nonspecific. In contrast, cultivars with high specific resistance were resistant for not more than 3 yr before new races that could circumvent the resistance became prevalent.