Evidence for the role of antibiosis in the antagonism of Chaetomium globosum to the apple scab pathogen, Venturia inaequalis

Abstract

Ascospore suspensions and culture extracts of Chaetomium globosum Kunze: Fr. reduced infection of apple seedlings by Venturia inaequalis (Cke.) Wint. (anamorph, Spilocaea pomi Fr.) in growth-chamber studies. An agar diffusion assay was developed to assess the relative fungistatic activity of culture extracts of C. globosum. No differences were observed in the sensitivity of 37 V. inaequalis strains to C. globosum extracts. Seven strains of C. globosum from diverse habitats were evaluated for antibiotic production in culture. Significant differences in antibiotic production between strains were observed, and antibiotic levels were positively correlated with antagonism to V. inaequalis on seedlings in growth-chamber studies. The antibiotic chetomin was tentatively identified in culture extracts by thin-layer chromatography and ultraviolet absorbance. The selection of high antibiotic producing strains of C. globosum may significantly improve antagonistic performance in the field.