Filamentous fungi isolated from grape marc as antagonists of botrytis cinerea

Abstract

In this paper we report on the isolation and identification of three filamentous fungi from grape marc, and antifungal effect of their cell-free culture filtrates on the growth of Botrytis cinerea, causal agent of gray mold. Grape marc is a waste material that has been used as soil amendment in sustainable agriculture. Isolates originating from grape marc were identified on the basis of morphological features and internal transcribed spacer rDNA or beta-tubulin gene sequencing. The presence of three different species, Penicillium paneum, Penicillium chrysogenum and Aspergillus fumigatus has been detected expressing different effect on the growth of B. cinerea. The effect of crude culture filtrates of selected fungi on B. cinerea growth was tested. Heat sensitivity of the established inhibition effect was examined by autoclaving the crude culture filtrate prior to testing. Additional aim was to determine whether antifungal effect was influenced by previous exposure to B. cinerea in dual liquid cultures. Crude culture filtrate of A. fumigatus K16/2 showed the lowest suppression of B. cinerea growth. A maximal percentage inhibition achieved within the study was 38.2%, 39.8% and 23.8 for crude filtrates of P. paneum K7/1, P. chrysogenum K11/1 and A. fumigatus K16/2, respectively. Presence of B. cinerea in dual liquid culture induced significant increase in antifungal capacity of the culture filtrates in comparison to pure culture filtrates of the chosen isolates. The antifungal activity of all of the isolates' culture filtrates retained after heat treatment suggesting the presence of some thermostable antifungal metabolites. The results indicate the complexity and specificity of the interaction between filamentous fungi and B. cinerea. Grape marc is a good source for isolation od B. cinerea fungal antagonists and their antifungal metabolites. Specificity of fungal-fungal interactions suggests that further research on the antagonistic mechanisms and factors affecting them should be studied separately for each pair of antagonists.