Chitinase and beta-1,3-glucanase enzyme production by the mycoparasite Clonostachys rosea f. catenulata against fungal plant pathogens.

Abstract

Clonostachys rosea f. catenulata (syn. Gliocladium catenulatum) is an effective fungal biological agent against Fusarium root and stem rot and Pythium damping-off diseases on cucumber plants. Both chitinase and beta-1,3-glucanase enzymes were produced when C. rosea was grown on a synthetic medium containing chitin or laminarin as a sole carbon source, respectively. Chitinase production was also induced by Fusarium cell walls, while beta-1,3-glucanase activity was induced by both Fusarium and Pythium cell walls, as well as by growth on homogenized cucumber roots and on low-carbon media. Mycelial growth of Fusarium and Pythium, when exposed to C. rosea culture filtrates that contain glucanase activity, was significantly reduced compared with the controls, and cell walls of both pathogens were degraded. On excised cucumber roots, hyphae of C. rosea formed appressorium-like structures and coiled around hyphae of Pythium. In culture, C. rosea caused localized degradation of Fusarium hyphae. Cucumber root tissues colonized by C. rosea showed higher levels of beta-1,3-glucanase activity at 7 days post-application compared with untreated controls. To determine if this activity was derived from C. rosea, glucanase isoforms were separated on activity gels. Fungal culture filtrates and root extracts contained the same predominant 20 kDa isoform. Reverse-transcription polymerase chain reaction (RT-PCR) using primers designed to amplify a beta-1,3-glucanase gene in C. rosea confirmed glucanase expression on roots. These results show that C. rosea produces beta-1,3-glucanase in situ, which can degrade hyphae of Fusarium and Pythium and contribute to biological control efficacy.