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Inheritance of Resistance to Pathotypes QCC and MCC of Puccinia graminis f. sp. tritici in Barley Line Q21861 and Temperature Effects on the Expression of Resistance. Y. Jin, Department of Plant Pathology, North Dakota State University, Fargo; B. J. Steffenson(2), and J. D. Miller(3). (2)Department of Plant Pathology, North Dakota State University, Fargo; (3)USDA-ARS, Northern Crop Science Laboratory, Fargo, ND 58105. Phytopathology 84:452-455. Accepted for publication 25 January 1994. 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, 1994. DOI: 10.1094/Phyto-84-452.

Barley line Q21861 is one of several accessions that possess resistance to pathotypes QCC and MCC of Puccinia graminis f. sp. tritici. Crosses were made between Q21861 and several barley cultivars to study the inheritance of resistance to pathotypes QCC and MCC. Progeny evaluations indicated that resistance to pathotype QCC in Q21861 was conferred by a recessive gene that conditioned low infection types at low incubation temperatures (1820 C). This gene was ineffective against pathotype QCC at incubation temperatures greater than 27 C. Resistance to pathotype MCC in Q21861 was controlled by two genes, one dominant and one recessive, that segregated independently. The dominant gene is allelic to Rpg1, and the recessive gene identified is the same one conferring resistance to pathotype QCC. This recessive gene is not allelic with Rpg2 based on an allelism test. It is unlikely allelic with Rpg3 based on reaction to pathotype QCC at the seedling stage, a recessive inheritance pattern, and temperature sensitivity. The locus and allele symbols Rpg4 and rpg4d, respectively, are suggested for the recessive gene in Q21861.