OCCURRENCE OF PLANT-PARASITIC NEMATODES AND NONPATHOGENIC SPECIES OF FUSARIUM IN TOMATO PLANTS IN KENYA AND THEIR ROLE AS MUTUALISTIC SYNERGISTS FOR BIOLOGICAL-CONTROL OF ROOT-KNOT NEMATODES

The occurrence of plant parasitic nematodes and endophytic fungi in tomato plants was determined from different regions in Kenya. In areas with regular cultivation of tomatoes, the population densities of all species of nematodes, regardless of trophic group, were high. Meloidogyne incognita was the predominant plant parasitic nematode in the regions investigated. Apparently endophytic fungi were frequently isolated from tomato roots, with Fusarium oxysporum being the most common endophyte detected. In contrast, irregular cultivation of tomato resulted in lower overall nematode densities and the absence of Meloidogyne infestation. 5. oxysporum occurred only sporadically. Four isolates of F. oxysporum, which were tested in subsequent greenhouse experiments, reduced M. incognita populations without adversely affecting plant health. Non-pathogenic isolates of F. oxysporum with mutualistic symbiotic behaviour are potential biological control agents for plant parasitic nematodes.