A Nondestructive Technique for Screening Bean Germ Plasm for Resistance to Meloidogyne incognita. C. O. Omwega, Graduate Research Assistant, University of California, Riverside 92521. I. J. Thomason, and P. A. Roberts. Professor of Nematology and Plant Pathology, University of California, Riverside 92521; and Extension and Associate Nematologist, University of California, Kearney Agricultural Center, Parlier 93648. Plant Dis. 72:970-972. Accepted for publication 28 June 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0970.

A technique to screen beans for resistance to root-knot nematodes based on egg mass counts was developed. Plants grown in seedling growth pouches were inoculated with 2,000 second-stage juveniles of Meloidogyne incognita race 1. Twenty-one days after inoculation, the roots were watered with erioglaucine dye (50 mg/ml) for 7 consecutive days. This dye stained the gelatinous matrix of the egg mass but not the female nematodes or the eggs. Stained egg masses were counted 28 days after initial inoculation. Egg mass counts were more highly correlated (r = 0.85) to egg counts than to either gall index (r = 0.45) or egg mass index (r = 0.56). Plants in growth pouches were then transplanted to pots containing UC mix soil and grown to maturity to test viability of the plants and to obtain seed from selected plants.

Keyword(s): Phaseolus spp.