Effectiveness of native West African arbuscular mycorrhizal fungi in protecting vegetable crops against root-knot nematodes

Twenty strains of arbuscular mycorrhizal fungi (AMF), native to West Africa, and three commercial AMF, were evaluated for their protective effect against root-knot nematodes, Meloidogyne spp., in pots and field experiments in Benin. In pots, these strains were assessed in sterilized soil following inoculation of nematodes and in non-sterilized soil naturally infested with nematodes using tomato. The four strains showing greatest potential in suppressing nematode development were further assessed in the field with a relatively high natural infestation level of nematodes (155 per 100 cm³ soil) over a tomato–carrot double cropping. In the pot experiments, most native strains provided significant suppression of nematode multiplication and root galling, but in most cases the level of nematode control depends on either sterilized or non-sterilized soils. In the field experiments, application of AMF mostly resulted in significant suppression of nematode multiplication and root galling damage on both crops indicating that the AMF persists and remains protective against root-knot nematodes over two crop cycles. Field application of AMF increased tomato yields by 26% and carrot yields by over 300% compared with the non-AMF control treatments. This study demonstrates for the first time, the protective effect of indigenous West African AMF against root-knot nematodes on vegetables. The potential benefits of developing non-pesticide AMF-based pest management options for the intensive urban vegetable systems are evident.