Biocontrol potential of nematophagous fungi against Meloidogyne spp. infecting tomato

Abstract

Root-knot nematodes are the most economically damaging group of plant parasitic nematodes. Intensive agriculture on sandy soil of Moroccan agroecosystems results in a prevalence and wide distribution of Meloidogyne spp., limiting both conventional and organic fruit and vegetable production. The aim of this study is to assess the nematicidal potential of twelve local isolates of nematophagous fungi in organic tomato production in laboratory and greenhouse conditions. Fungal isolates were of seven genera: Paecilomyces, Purpureocillium, Trichoderma, Fusarium, Talaromyces, Arthrobotrys, Dreschslerella, and Monacrosporium. In vitro assays screened the isolates for their ability to immobilize Meloidogyne javanica juveniles using 96-well tissue culture plates at a concentration of 106 spores.ml−1. The same isolates were tested for their potential to reduce M. javanica populations and galling on tomato roots in pot experiments with infested soil, applied upon transplantation at 107 spores.ml−1. Average mortality rate of second-stage juveniles of Meloidogyne spp. in vitro ranged from 11 to 42%, with a maximal range of 64 to 73% mortality. The highest rates of mortality were recorded after 72 h using Purpureocillium lilacinum and Arthrobotrys oligospora. In pot experimentation, the reproduction rate of root-knot nematodes ranged from 176 to 5920% with the gall index varying from 2.7 to 4.9 in treated pots. This study identified Paecilomyces and Arthrobotrys direct nematicidal effect against Meloidogyne spp., in laboratory conditions. To achieve successful control, further studies should be conducted to identify the optimal range of environmental factor practices which lead to the enhancement of biocontrol activity of these NF in the field.