Antifungal activity of Streptomyces albidoflavus L131 against the leaf mold pathogen Passalora fulva involves membrane leakage and oxidative damage

Passalora fulva (or Fulvia fulva) is the causal microorganism of tomato leaf mold, the outbreak of which occurs worldwide in greenhouse especially when humidity is high. However, studies on antifungal agents of P. fulva are still very limited. In this study, a marine-derived Streptomyces albidoflavus strain L131 showing potent inhibitory activities against P. fulva was identified and characterized. The active antifungal components were obtained, and studies on the antifungal mechanisms of the crude extract showed that the antifungal metabolites of L131 caused damage of hyphae and spore development, as well as plasma membrane of P. fulva. In addition, accumulation of endogenous reactive oxygen species of the leaf pathogen was also observed after treatment by culture extracts of L131. To our knowledge, this is the first report on the studies of the antifungal mechanisms against P. fulva, which benefit further development of biocontrol agent against tomato leaf mold disease.