Efficacy of SC5 Fermentation Filtrate in Inhibiting the Growth and Development in Sunflower.

is a destructive pathogen responsible for sunflower sclerotinia rot, resulting in substantial yield and economic losses worldwide. species have demonstrated the capacity to inhibit plant pathogen growth through the production of secondary metabolites. However, there are fewer recent studies focusing on the application of metabolites in inhibiting growth and development and controlling sunflower sclerotinia rot disease. Our results showed that five strains (SC5, T6, TN, P6, and TS3) exhibited mycelial growth inhibition higher than 60% in dual culture assays out of the 11 tested strains. The SC5 fermentation filtrate exhibited superior efficacy compared to other strains, achieving a 94.65% inhibition rate of mycelial growth on , 96% inhibition of myceliogenic germination of sclerotia, and 81.05% reduction in the oxalic acid content of , while significantly increasing the cell membrane permeability. In addition, the SC5 fermentation filtrate significantly decreased the activities of polygalacturonase and pectin methyl-galacturonic enzymes and even caused hyphae to swell, branch, twist, lyse, and inhibited the production and development of sclerotia. Moreover, the SC5 fermentation filtrate downregulated genes expression that associated with the growth and infection of . The control efficacies of the protective and curative activities of the SC5 fermentation filtrate were 95.45% and 75.36%, respectively, on detached sunflower leaves at a concentration of 8 mg/mL. Finally, the SC5 was identified as through morphological and phylogenetic analysis. Our research indicates that the SC5 can be considered a promising biological control candidate against and controlling the sunflower sclerotinia rot disease, both in vitro and in vivo.