Temperature-Specific Seedling Resistance and Adult-Plant Resistance to Puccinia recondita f. sp. tritici in the Wheat Cultivar Glenlea. Z. A. Pretorius, Grain Crops Research Institute, Bethlehem 9700, South Africa. F. H. J. Rijkenberg, and Roy D. Wilcoxson. Department of Microbiology and Plant Pathology, University of Natal, Pietermaritzburg 3200, South Africa; and Department of Plant Pathology, University of Minnesota, St. Paul 55108. Plant Dis. 72:439-442. Accepted for publication 23 September 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0439.

In a genetic study conducted in the F₁, F₂, and F₃ generations derived from the cross between line E (leaf rust susceptible) and cultivar Glenlea, a dominant gene for seedling resistance, presumably Lr1, and two recessive genes for adult-plant resistance to Puccinia recondita f. sp. tritici were indicated. Seedling tests with Glenlea and line E/Glenlea progenies at 29–31 C revealed that Glenlea has another gene in addition to Lr1. Expression of high-temperature seedling resistance in Glenlea was much more pronounced in progenies of the cross between line E and Glenlea than in the donor parent. Isolates detecting the temperature-specific gene were virulent to LrT2 (a gene for adult-plant resistance in Glenlea) in the seedling stage; some of these isolates, but not all, were virulent to Lr13 under similar conditions. Thus, the seedling resistance of Glenlea at 29–31 C is either mediated by the second gene for adult-plant resistance, which has been reported as allelic or closely linked with Lr13, or it may be a previously undetected gene. Determination of the specific environmental conditions required for expression of the genes for resistance to P. r. f. sp. tritici in Glenlea is valuable to breeding programs aimed at developing wheat genotypes with levels of resistance similar to that of Glenlea.