Enhancing tomato disease resistance through endogenous antifungal proteins and introduced nematode‐targeting dsRNA of biocontrol agent Bacillus velezensisHS‐3

Abstract

BACKGROUNDAs a type of biological control agents (BCAs), Bacillus velezensis possesses the efficacy of inhibiting pathogenic microorganisms, promoting plant growth, and overcoming continuous cropping obstacles (CCOs). However, there is limited reporting on the optimization of the cultivation conditions for such biocontrol agents and their role as dsRNA delivery vectors.RESULTSIn this study, a B. velezensis strain HS‐3 was isolated from the root zone of tomato plants with in vitro anti‐Botrytis cinerea activity. The investigation into active compounds revealed that HS‐3 predominantly employs proteins with molecular weights greater than 3 kDa for its antifungal activity. LC–MS/MS analysis identified various proteases and chitosanase, further suggesting that HS‐3 most likely employs these enzymes to degrade fungal cell walls for its antifungal effect. To optimize the production of extracellular proteins, fermentation parameters for HS‐3 were systematically optimized, leading to an optimized medium (OP‐M). HS‐3 cultured in OP‐M demonstrated enhanced capacity to assist tomato plants in withstanding CCO. However, the presence of excessive nematodes in diseased soil resulted in disease severity index (DSI) remaining high. An RNA interference mechanism was further introduced to HS‐3, targeting the nematode tyrosine phosphatase (TP) gene. Ultimately, HS‐3 expressing dsRNA of TP in OP‐M effectively assisted tomatoes in mitigating CCO, reducing DSI to 2.2% and 17.8% of the control after 45 and 90 days of growth, respectively.CONCLUSIONThe advantages of Bacillus velezensis in crop disease management and the mitigation of CCOs become even more pronounced when utilizing both optimized levels of endogenous enzymes and introduced nematode‐targeting dsRNA.