Abundance anddiversity of bacillus subtilis andplant parasitic nematodes affecting common bean (phaseolus vulgaris) under different soil fertility management systems

Abstract

Plant parasitic nematodes cause an estimated US$100 billion in damage to agricultural crops worldwide and the most studied natural enemies of nematodes are bacteria and fungi. This study sought to evaluate the influence of soil fertility management practices on the diversity of plant parasitic nematodes associated with common bean. Two experiments were laid on farmers fields (onfarm) and on the farmers training centre (on-station) in Embu in a randomized complete block design where common bean variety GLP -2 was planted in an intercrop with maize variety H513. The treatments included manure, mavuno, and manure in combination with Bacillus subtilis, mavuno in mixture with B. subtilis, farmer practice and farmer practice combined with B. subtilis. A greenhouse experiment was conducted to compare the effects of Bacillus isolates on plant parasitic nematodes under sterile and non-sterile soil conditions and laid as a completely randomized design replicated 12 times. Data on Galling index and initial and final plant parasitic nematode count was taken. Rotylenhus and Meloydogyne were the most abundant plant parasitic nematode genera in Embu with 20% and 15% of the total nematodes respectively. B. subtilis combined with manure led to highest (89%) reduction in plant parasitic nematodes. B. subtilis and manure led to the least damage to bean roots in the On-station and onfarm experiments with galling indices of 1.6 and 1.8 respectively hence attributed to the effective control of Meloydogyne spp. Plant Parasitic Nematodes associated with beans are prevalent in Embu and can be effectively controlled by the use of manure, B. subtilis K194 combined with manure and by farmer practice.