Parasitism of Trichoderma on Meloidogyne javanica and role of the gelatinous matrix

Authors: SHARON, EDNA - ISRAEL; CHET, ILAN - ISRAEL; VITERBO, ADA - ISRAEL; BAR-EYAL, MIERA - ISRAEL; NAGAN, HAREL - ISRAEL; Samuels, Gary; SPIEGEL, YITZHAK - ISRAEL

Submitted to: European Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2007
Publication Date: 5/8/2007
Citation: Sharon, E., Chet, I., Viterbo, A., Bar-Eyal, M., Nagan, H., Samuels, G.J., Spiegel, Y. 2007. Parasitism of Trichoderma on Meloidogyne Javanica and role of the Gelatinous Matrix. European Journal of Plant Pathology. 118:247-258.

Interpretive Summary: Nematodes cause serious damage to crop plants and are controlled primarily by chemicals. At present non-chemical methods to control nematodes are urgently needed. Used primarily in the control of plant pathogens, fungi in the genus Trichoderma have not been examined for control of nematodes. In this study three species of Trichoderma were tested and found to parasitize egg masses of a nematode that parasitzes tomatoes. The conditions and mechanism of successful parasitism were explored. This research will be used by plant pathologists who are working to develop non-chemical methods to control plant parasitic nematodes.

Technical Abstract: Trichoderma (T. asperellum-203, 44 and GH11; T. atroviride-IMI 206040 and T. harzianum-248) parasitism on Meloidogyne javanica life stages was examined in vitro. Conidium attachment and parasitism differed among the various fungi. Egg masses, their derived eggs and second-stage juveniles (J2) were parasitized by T. asperellum-203, 44, and T. atroviride following conidium attachment. T. asperellum-GH11 attached to the nematodes but exhibited reduced penetration, whereas growth of T. harzianum attached to egg masses was inhibited. Only few conidia of the various fungi were attached to eggs that lacked a gelatinous matrix; nevertheless, they were penetrated by hyphae. Gelatinous-matrix-free J2s also presented very low conidium attachment and they were rarely parasitized by the fungi. The gelatinous matrix specifically induced J2 immobilization by T. asperellum-203, 44 and T. atroviride metabolites. A constitutive-GFP-expressing T. asperellum-203 construct was used to visualize fungal penetration of the nematodes. Scanning electron microscopy revealed the formation of coiling and appressorium-like structures upon attachment and parasitism by T. asperellum-203 and T. atroviride. Gelatinous matrix agglutinated T. asperellum-203 and T. atroviride conidia, a process that was Ca2+-dependent. Conidium agglutination was inhibited by carbohydrates, including fucose, as was conidium attachment to the nematodes. All but T. harzianum could grow on the gelatinous matrix, which enhanced conidium germination. A biomimetic system based on gelatinous-matrix-coated nylon fibers demonstrated the role of the matrix in parasitism: T. asperellum-203 and T. atroviride conidia attached specifically to the gelatinous-matrix-coated fibers and parasitic growth patterns were induced in both fungi. Parasitic interactions were demonstrated in planta with T. asperellum-203-GFP, which colonized tomato roots and interfered with J2 penetration. Females and egg masses dissected from tomato roots grown in T. asperellum-203-treated soil were parasitized by the fungus. This study demonstrates Trichoderma parasitic ability on different M. javanica life stages and the importance of the gelatinous matrix conidium attachment and parasitism processes.