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Resistance

Resistance of Barley to Puccinia graminis f. sp. tritici and Puccinia graminis f. sp. secalis. Brian J. Steffenson, Former research assistant, Department of Plant Pathology, University of Minnesota, St. Paul 55108, Present address: Department of Plant Pathology, University of California, Davis 95616; Roy D. Wilcoxson(2), and A. P. Roelfs(3). (2)Professor, Department of Plant Pathology, University of Minnesota, St. Paul 55108; (3)Research plant pathologist, Cereal Rust Laboratory, Agricultural Research Service, U.S. Department of Agriculture, St. Paul, MN 55108. Phytopathology 75:1108-1111. Accepted for publication 10 May 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-1108.

Seedlings of barley cultivars possessing the T-gene developed low weighted infection types that indicated the plants were resistant when infected with races 113-RTQ, 151-QSH, and 29-HJC of Puccinia graminis f. sp. tritici. However, four cultivars that lack the T-gene had low weighted infection types that were not significantly different from those displayed by the T-gene cultivars to either or both race 113-RTQ and 151-QSH. This suggests that these cultivars possess resistance gene(s) that are different from the T-gene. Race 29-HJC most clearly distinguished the cultivars with the T-gene from those without it. When barleys were infected with race HQ of P. graminis f. sp. secalis, seedlings of most cultivars developed relatively low weighted infection types; Heitpas-5 and Steptoe had the highest weighted infection types. Barleys possessing the T-gene could not be distinguished from those cultivars without the gene to this race of the rye stem rust pathogen. In the field, cultivars with and without the T-gene were tested with a composite of races 113-RTQ, 151-QSH, 29-HJC, 151-QFB, and 15-TNM of P. graminis f. sp. tritici. Terminal rust severities and the type of uredia present on plants indicated that barleys with the T-gene were moderately resistant to moderately susceptible to this composite of races. In the group of cultivars lacking the T-gene, Heitpas-5, and Black Hull-less were moderately susceptible, whereas the other cultivars were susceptible. In field tests with race HQ of P. graminis f. sp. secalis, Black Hull-less was resistant and Valkie, Hispont, and Heitpas-5 were moderately resistant. The cultivars with the T-gene were susceptible to moderately susceptible and could not be distinguished from some barleys that lack the T-gene.