Functional Screening and Biochemical Correlates of Streptomyces Antagonism Against Fusarium sp.

Abstract

Although antagonistic Streptomyces are widely recognized for their antifungal potential, trait-based selection of effective isolates remains insufficiently explored. In this study, we recovered thirty-eight Streptomyces-like actinomycete isolates from agricultural soils and screened them for antifungal activity against Fusarium sp. using a dual-culture assay. We further evaluated antagonistic isolates for chitinase activity, total protein content, and Folin–Ciocalteu-reactive phenolic-equivalent content. We conducted correlation analyses to examine associations between these biochemical traits and fungal growth inhibition. Sixteen isolates (42%) exhibited antifungal activity, with inhibition values ranging from 1.84 to 69.20%, while isolates VAS10 and VAS35 achieved at least 65% suppression. Among the measured traits, chitinase activity showed the strongest positive association with fungal growth inhibition, followed by Folin–Ciocalteu-reactive phenolic-equivalent content. In contrast, total protein content was not significantly associated with inhibition. These results suggest that chitinase activity may serve as a preliminary screening indicator associated with antifungal performance; however, the correlation analysis and limited biochemical measurements do not establish causality or define the underlying antifungal mechanism. Accordingly, the present findings support the prioritization of VAS10 and VAS35 for further validation but do not demonstrate their efficacy in planta or establish them as validated biocontrol agents.