Efficacy of Trichoderma harzianum, Bacillus cereus and Their Lytic Enzymes for the Control of Damping-Off Disease of Yard Long Bean Caused by Pythium aphanidermatum

摘要

The indigenous antagonistic microorganisms Trichoderma harzianum and Bacillus cereus and their lytic enzymes (beta-glucanase and cellulase) were used to control the damping-off disease of yard long bean (Vigna sesquipedalis L.). T. harzianum strain NST-02 and B. cereus strain NST-03 produced high levels of crude enzymes, both cellulase and (3-1,3-glucanase, which highly inhibited the mycelial growth of Pythium aphanidermatum. Under greenhouse conditions, T. harzianum NST-02, B. cereus NST-03 and their crude enzymes were able to induce the resistance-related enzymes polyphenol oxidase and phenylalanine ammonia-lyase. In all treatments, the level of Pyfri/um-associated damping-off disease was reduced compared with the control treatment (water). For the field experiments, combination of T. harzianum NST-02, B. cereus NST-03 and their crude enzymes provided increased efficacy for the control of Pyr/r/um-associated damping-off disease compared with the application of either T. harzianum NST-02 or B. cereus NST-03 alone. The treatment that used T. harzianum NST-02, in combination with the crude cellulase and p-1,3-glucanase enzymes, resulted in the lowest incidence of disease, but it was not significantly different from the incidence achieved when the synthetic chemical metalaxyl was used. Reduction in the level of damping-off disease due to use of the combined treatment consisting of T. harzianum NST-02 and the crude cellulase and beta-1,3-glucanase enzymes resulted in the highest yield and the longest length of yard long bean pods. In addition, combination of T. harzianum and 6. cereus treatments, with crude cellulase and beta-1,3-glucanase enzymes, promoted an increase in T. harzianum and B. cereus populations and root colonization and resulted inthe increased efficacy of the control of damping-off disease in yard long bean compared with treatments that used T. harzianum and B. cereus alone.