Plant Parasitic Nematodes Associated with Common Bean In Kenya and the Effect of Meloidogyne Infection On Bean Nodulation

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.Une \ue9tude pour d\ue9terminer la distribution et la densit\ue9 de la population de n\ue9matodes parasitaires de plantes associ\ue9s aux haricots a \ue9t\ue9 initi\ue9 dans les districts de Kakamega, Kiambu, Machakos et Siaya au Kenya. Les \ue9chantillons des racines et de sols ont \ue9t\ue9 pris dans 25 fermes s\ue9lectionn\ue9es al\ue9atoirement dans chaque districts. Les n\ue9matodes des genres Meloidogyne, Pratylenchus, Scutellonema et Helicotylenchus ont \ue9t\ue9 fr\ue9quemment trouv\ue9s dans la rhizosph\ue8re des plantes de haricot avec des densit\ue9 vari\ue9es dans differentes parties du pay. Meloidogyne spp. et Pratylenchus spp. \ue9taient des endoparasites les plus dominants apparaissant dans 86 et 67% d\u2019\ue9chantillons de racines, respectivement. Les esp\ue8ces de Scutellonema et Helicotylenchus \ue9taient pr\ue9sents dans 80 et 59% d\u2019\ue9chantillons de sol respectivement. Autres n\ue9matode trouv\ue9s en assoication avec la plante de haricot \ue9taient des genres de Tylenchorhynchus, Tylenchus, Criconemella, Aphelenchus, Hemicyliophora et Trichodorus. Avec exception du g\ue9notype M28, l\u2019infection du Meloidogyne a caus\ue9 de r\ue9duction significative (P<0.05) dans la nodulation. Dans le deuxi\ue8me essai en pots des combinaisons de haricot avec M. incognita ont \ue9t\ue9 consid\ue9r\ue9es. Ensemble les processus de dinitrification et de nodulation ont \ue9t\ue9 d\ue9favorablement affect\ue9s sp\ue9ciallement dans les plantes o\uf9 les n\ue9matodes ont pr\ue9c\ue9d\ue9 l\u2019inoculation du Rhizobium