Plant parasitic nematodes associated with common bean in Kenya and the effect of Meloidogyne infection on bean nodulation

Abstract

A study to determine the distribution and population densities of plant parasitic nematodes associated with beans was undertaken in Kakamega, Kiambu, Machakos and Siaya districts of Kenya. Soil and root samples were taken from 25 randomly selected farms in each district. Nematodes in the genera Meloidogyne, Pratylenchus, Scutellonema and Helicotylenchus were frequently recovered in the rhizophere of bean plants with varying densities in the different locations of the study. Meloidogyne spp. and Pratylenchus spp. were the most predominant endoparasites occurring in 86 and 61% of the root samples, respectively. Scutellonema and Helicotylenchus species were present in 80 and 59% of the soil samples, respectively. Other nematodes found in association with bean plants were in the genera Tylenchorhynchus, Tylenchus, Criconemella, Aphelenchus, Hemicyliophora, and Trichodorus. Greenhouse tests were conducted to determine the effect of M. incognita infection on nodulation of bean genotypes. With the exception of bean genotype M28, Meloidogyne infection caused significant (P< 0.05) reductions in nodulation. In a second pot experiment, bean cv. GLP-24 was inoculated with Rhizobium leguminosarum bv. phaseoli alone and in various combinations with M. incognita. Both nodulation and the dinitrogen fixation processes were adversely affected especially in plants where nematode inoculation preceded rhizobial inoculation.