VIEW ARTICLE

Genetics

A New Allele at the Rps₃ Locus for Resistance to Phytophthora megasperma f. sp. glycinea in Soybean. L. D. Ploper, Graduate research assistant, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907; K. L. Athow(2), and F. A. Laviolette(3). (2)(3)Professor, and associate professor, respectively, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907. Phytopathology 75:690-694. Accepted for publication 23 January 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-690.

The genetics of resistance to Phytophthora megasperma f. sp. glycinea was studied in soybean (Glycine max) PI 172901, which was resistant to races 1 through 16 of the pathogen. PI 172901 was crossed to Harosoy (rps), Mukden (Rps₁), Sanga (Rps₁^b), Wells II (Rps₁^c), Williams 82 (Rps₁^k), PI 86972-1 (Rps₃), PRX27-108 (Rps₁ Rps₄), and Altona (Rps₆). The F₂ populations and the progenies of F₂ plants from each cross were evaluated for their reaction to physiologic races 1, 2, 3, 4, 5, 7, and 9 of the fungus. The results showed that there were two independent, dominant genes for resistance in PI 172901. One was Rps₁^b which gives resistance to races 1, 3, 4, 5, 7, and 9, and susceptibility to race 2. The other gene was an undescribed allele at the Rps₃ locus which confers resistance to the seven physiologic races included in this study. The symbol Rps₃^b was proposed for this gene to indicate a second allele at the Rps₃ locus and to discriminate it from the gene Rps₃ which conditions susceptibility to race 7.