Study on the antifungal effect and mycolytic activity of the biocontrol agent Chaetomium subaffine LB-1

Abstract

The antifungal effect and mucolytic activity of a newly screened biocontrol strain Chaetomium subaffine LB-1 were researched in this study. The results found that LB-1 has good antifungal effects on the test plant pathogenic fungi Botrytis cinerea Pers. ex Fr., Fusarium oxysporum f. sp. cucumerinum Owen and Alternaria solani (Ellis & Martin) Sorauer in dual culture assay, with the inhibition rates of 61.39, 50.34 and 51.22%, respectively. Flocculated and dissolved hyphae of the phytopathogenic fungi were observed at the interaction zone on a dual-cultured PDA plate, but the hyphae of LB-1 were normal. The LB-1 cell-free filtrate has significant inhibitory effects on the three tested fungi in the poison plate assay; dissolved colonies, vesiculated and flocculated hyphae of the test pathogenic fungi were also found on the PDA plates supplemented with the LB-1 cell-free filtrate. Clear halo zones around the LB-1 colonies were found on the protease test plate, pectinase test plate and cellulose test plate, indicating that LB-1 could produce mucolytic enzymes of protease, pectinase and cellulase. However, the activities of chitinase and β-l,3-glucase were not detected on their test plates from LB-1. An obvious oil-displaced circle was formed in the oil spreading test, indicating that a surface-active substance might be contained in the LB-1 cell-free filtrate. These results proved that the biocontrol agent of C. subaffine LB-1 could exert its antifungal effects via living competition and mycolysis, and the latter may be obtained by production of mycolytic enzymes and surface-active substances. .