A Nondestructive Technique for Screening Bean Germ Plasm for Resistance to Meloidogyne incognita

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Abstract
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 inocuation. 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 plots containing UC mix soil and grown to maturity to test viability of the plants and to obtain seed from selected plants.