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Genetics

A Single Dominant Gene in Common Bean Conferring Resistance to Three Root-Knot Nematode Species. C. O. Omwega, Former graduate student, Department of Nematology, University of California, Riverside 92521; I. J. Thomason, and P. A. Roberts. Professor of nematology and plant pathology, and Associate professor, respectively, Department of Nematology, University of California, Riverside 92521. Phytopathology 80:745-748. Accepted for publication 7 February 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/Phyto-80-745.

Resistance to root-knot nematodes, Meloidogyne javanica, M. incognita race 1, and M. arenaria has been identified in common bean landraces G2618 and G1805 and in the breeding lines A445, A315, and others derived from them. The mode of inheritance of the resistance gene from the two sources was studied. The data obtained showed that the resistance from the two sources was conditioned by a single dominant gene. No segregation was observed in the F₂ populations of the crosses between resistant parents A445 × A315 and G2618 × G1805, indicating that resistance from the two sources was allelic. In the split-rooted F₂ plants of the cross A445 × cultivar Kentucky Wonder (KW) (susceptible parent) where each plant was inoculated with a different nematode isolate on each half of the root system, all the plants had the same reaction on both halves of the root system in all nematode combinations. Plants of 14 F₃ families of the cross A445 × KW showed that all families reacted the same way to M. javanica, M. incognita race 1, and M. arenaria race 1. These data were consistent with the hypothesis that the same gene conferred resistance to the three root-knot nematode species. We propose the symbol Me1 for this gene.