Acyldepsipeptide 1 and Furan Derivative from Pseudomonas chlororaphis Are Critical for Biocontrol of Tomato Bacterial Wilt Caused by Ralstonia solanacearum

Abstract Tomato bacterial wilt, caused by Ralstonia solanacearum, is a destructive soil-borne disease that severely constrains tomato production. Here, we compared two rhizosphere bacterial strains Pseudomonas chlororaphis subsp. aurantiaca YS05 and YS21, with contrasting biocontrol efficiency. YS05 strongly suppressed disease, whereas YS21 showed substantially weaker efficacy. Comparative analyses indicated that both strains shared conserved genomic architecture and colonization-associated traits, but YS05 uniquely harbored secondary metabolite (SM) biosynthetic gene clusters (BGCs) associated with acyldepsipeptide 1 (ADEP1), furan derivative, and arylpolyene. Deletion of adeB or avrD reduced metabolite accumulation and biocontrol efficacy, whereas neither YS05 derivatives nor the corresponding metabolite standards directly inhibited R. solanacearum in vitro; instead, they activated tomato defense responses associated with salicylic acid, jasmonic acid, and reactive oxygen species homeostasis. These findings link ADEP1 and furan derivative to YS05-mediated bacterial wilt suppression and defense activation, and offer new insights into the development of environmentally friendly biocontrol agents.