Nematicidal Effect of Three Trichoderma spp. on the Suitability of Tomato Plants for Meloidogyne incognita Reproduction

Abstract

Soil-borne root-knot nematode (RKN) Meloidogyne incognita, has become a chronic pest that must be dealt with repeatedly every season, particularly during flowering and fruiting periods. So, this situation heightens to search for safe, effective, and extended-release alternatives for chemical nematicides to combat RKN. So, the potential nematicidal activity of Trichoderma album, T. harzianum and T. viride against RKN eggs hatching and second stage juveniles (J2) survival was determined in vitro, besides their interaction effect on reducing reproduction factor (Rf) of M. incognita in infected tomato roots in pot soils and promoting plant growth parameters under subtropical greenhouse conditions. In vitro, Trichoderma spp. showed a limited nematicidal effect against RKN with the various concentrations. T. viride exhibited a weak nematicidal effect against eggs and J2 of RKN. Moreover, the concentration of 1×10 8 spores/ml displayed maximum ovicidal effect on RKN eggs and T. album potency surpassed T. viride. Conversely, T. harzianum caused the highest significant ovicidal and larvicidal effect at the concentrations of 1×10 7 and 1×10 8 spore/ml and exceeded oxamyl potency after 6 days with eggs and at 1×10 8 spore/ml after 14 days incubation with J2s. Generally, Trichoderma spp. showed a significant ovicidal effect against RKN surpassing oxamyl nematicide in contrast to the larvicidal effect which was very limited compared with oxamyl. In pots, plants inoculated with Trichoderma spp. achieved higher plant fitness indices compared to the control, presumably related to changes in plant resistance after proving Trichoderma root colonization. The number of galls/root, egg masses/root, J2s/100 g soil, eggs/100 g soil and Rf in Trichoderma treatments showed a mediated significant reduction lower than oxamyl potency which ascertained the ability of Trichoderma spp. with various concentrations to keep RKN population below the economic threshold or avoid plant damage resulted from RKN infection by multiple mechanisms of action including parasitism, root colonization, plant resistance and growth promoting.