Evaluation of different isolates of Trichoderma spp. for antagonistic activity against Meloidogyne incognita

Although better known as mycoparasites, fungi of the genus Trichoderma have been reported to control phytoparasitic nematodes in vitro and in the field. In this study, a series of experiments were carried out to assess the activity of different isolates of Trichoderma spp. against the root-knot nematode Meloidogyne incognita. An in vitro screening of culture extracts of Trichoderma strains was carried out to assess the production of anti-nematode compounds. Fungal extracts were tested in vitro for their activity on egg hatching and nematode juveniles (J2) mobility. Mortality rates of M. incognita J2 treated with the fungal extracts varied largely among the strains tested, ranging from no activity to almost complete kill of J2 within 24-hours. Based on these results, greenhouse trials were conducted to assess the anti-nematode capability of Trichoderma isolates in planta (semi-field conditions) on the tomato susceptible cv. Regina. Fungal suspensions (10 mL of a conidial suspension 107 Cfu/mL) were applied either by seedling tray drench 2 weeks before transplanting or at the same time of transplanting in pre infested soil (5 eggs and J2 per g/soil). The control of M. incognita infestation was assessed by nematode multiplication rate and gall formation on tomato roots 60 days post infestation (dpi). Soil treatments with fungal spore preparations were found to suppress both nematode multiplication and gall formation on tomato roots, but the suppressive potential was largely variable among the different fungal isolates. Nematode response to soil treatment with the same Trichoderma isolates was also tested in growth chamber experiments, on tomato plants grown in 50 ml clay pots, each treated with 5 mL of a 107 cfu/mL conidial suspension. Nematode penetration and development in tomato roots were observed at 2, 7, 15 and 35 dpi under a stereomicroscope. Reduction in gall number and female fecundity were observed, particularly when the fungal spores were applied at the same time of J2 inoculation. These results indicate that an appropriate selection of Trichoderma isolates can allow the development of effective biocontrol formulations for safe management of root-knot nematodes.