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Resistance

Effect of Temperature on Adult-Plant Resistance to Leaf Rust in Wheat. Kalpana Kaul, Former graduate research assistant, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, Present address: Department of Plant Pathology, Pennsylvania State University, University Park 16802; Gregory Shaner, professor, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907. Phytopathology 79:391-394. Accepted for publication 10 October 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/Phyto-79-391.

Adult-plant resistance provides an important type of protection against leaf rust for soft red winter wheat in the northern part of its range in the United States. In breeding for this resistance and studying its inheritance, we noted that its expression seemed to be influenced by temperature. Experiments were conducted under controlled temperature conditions to examine this phenomenon in greater detail. Several wheat breeding lines and three cultivars were vernalized and then grown in the greenhouse or in growth chambers programmed for various diurnal temperature regimes, ranging from 15/12 to 30/21 C (day/night). Plants were inoculated with a pure culture of Puccinia recondita after flag leaves had emerged. The cultivar Morocco, the susceptible control, was consistently susceptible, of infection type (IT) 3⁺. Temperature induced major differences in ITs in all but three lines with adult-plant resistance: P75438, P76603, and P69195, which were of IT 0 or IT 0c at all temperatures. None of the lines developed a susceptible reaction (IT 3⁺) at the lowest temperature regime, whereas all temperature-sensitive lines developed at least a few IT 3⁺ uredinia at the highest temperature regime. P77121 showed a sudden loss of resistance at high temperature. Coker 79-14, P751909, P76905, and P76779 showed a gradual shift to higher ITs as temperature increased. P751915 remained resistant only over a narrow range of temperature. P74140-6 and P74140-7 showed a higher IT at both high and low temperatures than at intermediate temperatures. The cultivar Compton showed a few IT 3⁺ when grown continuously at 30/21 C, but not when reared at a lower temperature until inoculation.