Reactions of lines of Phaseolus atropurpureus to four species of root-knot nematode

Abstract

In each of two years the reactions of 36 lines of Phaseolus atropurpureus to the four root-knot nematodes Meloidogyne arenaria, M. hapla, M. incognita, and M. javanica were studied. Seven of the experimental lines were common to the two years. Two known susceptible species, Phaseolus lathyroides and Lycopersicon esculentum (tomato cv. Grosse Lisse), were used as controls. Four macroscopic and four microscopic reactions were recorded on each occasion, and the results analysed. Resistance to the four nematodes was present in all lines of P. atropurpureus. There was also evidence of differential resistance between lines; some showed increased resistance to all nematodes except M. hapla, and others showed both increased susceptibility to M. hapla and increased resistance to M. javanica. The severity of attack on thc controls was significantly less in the second ycar. Several explanations for this are advanced.