Predominance of a single major gene for resistance to phakopsora pachyrhizi in a population of glycine argyrea

Abstract

Four phenotypic patterns of resistance and susceptibility to nine races of Phakopsora pachyrhizi were found among 104 lines derived from seeds collected from 49 plants of a Glycine argyrea population. Genetic analyses suggested that the three most common phenotypic patterns were determined by two alleles ai a single locus. The fourth phenotypic pattern was represented by only a single line which was not analyzed genetically. These results contrast with those of a related species, G. canescens, where ten or more resistance genes were detected within each of two populations, and individuals often possessed two or more resistance genes. It is postulated that G. argyrea’s relatively high rate of outcrossing and the apparent prevalence of forms of resistance which delay the development of the pathogen may have contributed to the small number of major resistance genes in this population. © 1990 The Genetical Society of Great Britain.