Biocontrol potential of a native species of Trichoderma longibrachiatum against Meloidogyne incognita

Meloidogyne incognita is one of the most important soil-borne and plant parasitic pathogens in cucumber worldwide. An ideal strategy is to develop and use effective and environmentally-friendly bio-control agents to control the plant parasitic pathogen M. incognita. This study determined the biocontrol efficacy of Trichoderma longibrachiatum, a fungal species native to China, against M. incognita. In vitro, T. longibrachiatum at the concentrations of 1.5 × 105 to 1.5 × 107 conidia ml−1 had a strong lethal and parasitic effect on the second stage juveniles of M. incognita, with the concentration of 1.5 × 107 conidia ml−1 inhibited and parasitized the second stage juveniles >88% 14 days after treatments. Microscope observations revealed that after the mutual recognition with the second stage juveniles, the conidia of T. longibrachiatum adhered or parasitized on the surface of second stage juveniles, germinated with a large number of hyphae and penetrated the integument, and was reproduced on the surface of second stage juveniles. Meanwhile, the surface of second stage juveniles became deformed and some were completely dissolved by the metabolite of T. longibrachiatum. The maximum protease activity of T. longibrachiatum was 3.35 U min−1 ml−1 at the 5th day after the treatment of second stage juveniles. In greenhouse experiments, the concentrations of T. longibrachiatum ranging from 1.5 × 105 to 1.5 × 107 conidia ml−1 all decreased M. incognita infection and increased plant height, root length, shoot and root fresh weights in cucumber significantly compared to the control. T. longibrachiatum can be considered to be a promising bio-control agent against M. incognita with a high efficacy.