Extracellular enzyme production and fungal mycelia degradation of antagonistic Streptomyces induced by fungal mycelia preparation of cucurbit plant pathogens

Abstract

Streptomyces are beneficial soil microorganisms and potential candidates for biocontrol agents against soilborne pathogenic fungi of cucurbit plants. Extracellular enzymes such as cellulase, chitinase and glucanase produced by Streptomyces are important components of actinomycete-fungus antagonism. This study aimed to investigate the influence on extracellular enzymes production and fungal mycelia degradation by antagonistic Streptomyces of mycelia preparation of pathogenic fungi (MPPF) of cucurbit plants. The results showed that the antagonistic Streptomyces displayed high extracellular enzyme activities to varying degrees when MPPF was used as the sole carbon source. The MPPF from Fusarium proliferatum, Fusarium oxysporum f. sp. niveum and Alternaria tenuissima were the most effective carbon sources in enhancing the cellulase activity of Streptomyces globisporus C7, Streptomyces globisporus subsp. globisporus C28 and Streptomyces kanamyceticus C49, respectively. S. globisporus subsp. globisporus C28, Streptomyces pactum A12 and S. kanamyceticus C49 cultured in the medium containing MPPF from Fusarium equiseti showed the highest chitinase activity (12.35, 12.50 and 15.06 U, respectively) of all the MPPF treatments. Glucanase activity of Streptomyces carnosus A11 was enhanced greatly (9.26 U) when MPPF from A. tenuissima was used as the sole carbon source. A hyphal intertwining and degradation phenomenon was observed when the antagonistic Streptomyces came across the pathogenic fungal mycelia, which was due to a synergistic effect of the extracellular enzymes produced by the antagonistic Streptomyces.