Identification of the biocontrol strain LB-2 and determination of its antifungal effects on plant pathogenic fungi

Abstract

Biocontrol agents are key players in plant disease control. In this study, a potential biocontrol strain LB-2 was identified as Chaetomium globosum based on morphological observations and rDNA-ITS sequence analysis. The antifungal effect of LB-2 was determined with a dual culture assay showing that the mycelial growth of Botrytis cinerea, Fusarium oxysporum f. sp. cucumerinum, and Exserohilum turcicum was inhibited by LB-2, their hyphae at the colony contact surface being swollen and shrunken. Poison plate assay indicated that cell-free culture broth of LB-2 and its butanol and ethyl acetate (EtOAc) crude extracts exerted strong antifungal effects on the mycelial growth of the three tested phytopathogenic fungi, with the highest inhibition rate (89.99%) on E. turcicum induced by the butanol crude extract. Disease indices of northern corn leaf blight (caused by E. turcicum) in potted maize seedlings could significantly be reduced (P < 0.05) by foliar spraying of the cell-free culture broth, butanol and EtOAc crude extracts of LB-2. The highest disease control efficacy (53.47%) was shown by butanol crude extract. However, no antifungal effect was produced by the intracellular fluid of LB-2 in both in vitro and in vivo experiments. These results demonstrated that LB-2 is a promising Chaetomium spp. biocontrol agent against phytopathogenic fungi. Its antifungal effects might be achieved through a combination of living competition and production of antifungal substance, which are excreted by the mycelial cells.