Identification and Application of <i>Streptomyces rapamycinicus</i> CQUSh011 against Potato Late Blight

Using chemical fungicides is the main strategy for controlling potato late blight (PLB), a devastating pre- and postharvest disease caused by <i>Phytophthora infestans</i>, resulting in environmental pollution and health risks. It is of great importance to develop a biofungicide from microorganisms. Through isolating potato rhizosphere microorganisms, CQUSh011 was found to have antioomycete activity with strong inhibition on vegetative growth and virulence of <i>P. infestans</i>. Morphological and molecular identification indicated that CQUSh011 belongs to <i>Streptomyces rapamycinicus</i>. Based on genome, metabolome, and HPLC quantification, rapamycin and salicylic acid were found to be the two active metabolites against <i>P. infestans</i>. Continuous field trials showed that CQUSh011 has sustainable control efficiency against PLB, and the efficiency was better when combined with Infinito, along with an increased endophytic microbial community and biodiversity in potato roots. The results demonstrated the potential of CQUSh011 as a biofungicide against PLB and provided an alternative strategy for reducing the application of chemical fungicides.