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Resistance of Durum Wheats Used as Differential Hosts for Stem Rust. N. Bolat, Former Graduate Student, Department of Plant Pathology, University of Minnesota, St. Paul 55108. A. P. Roelfs, Cereal Rust Laboratory, Agricultural Research Service, U.S. Department of Agriculture, University of Minnesota, St. Paul 55108. Plant Dis. 75:563-568. Accepted for publication 8 October 1990. 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, 1991. DOI: 10.1094/PD-75-0563.

Durum wheat (Triticum turgidum) cultivars (Mindum, Spelmar, Arnautka, Kubanka, Acme, Golden Ball, and Entrelargo de Montijo) used as standard or supplemental differentials for wheat stem rust were studied for resistance to selected pathogen cultures in the seedling stage. The presence of Sr9d in Mindum, Spelmar, and Arnautka was verified by using an avirulent race, Pgt-MCC, to inoculate F1, F2, and F3 plants from crosses of these cultivars with the susceptible cultivar Glossy Hugenot. Mindum and Spelmar had an additional incompletely recessive gene for resistance to the race Pgt-QTH, and Arnautka had a dominant gene for resistance to Pgt-GMC. Tests of F1, F2, and F3 plants from crosses of Kubanka and Acme with Glossy Hugenot indicated that, in addition to Sr9g (verified by using race Pgt-QBB), both cultivars have a single dominant resistance gene to Pgt-QTH. The F1 and F2 seedlings of Glossy Hugenot/Golden Ball indicated that the same or an allelic incompletely dominant gene(s) conditioned resistance of Golden Ball to races Pgt-TPM and Pgt-QBB. However, the low infection type expressed by infection with these two cultures differed. Entrelargo de Montijo had two recessive genes for resistance to Pgt-QTH. Continuous variation to Pgt-MCC in low infection type was found in the F2. However, about one of 64 of the F2 plants gave a reaction similar to that of the resistant parent indicating three recessive resistance genes. Resistance to these two races may be conditioned by five genes.