Root rot of strawberry caused by Fusarium citri in China and use of Streptomyces rhizosphaericus as a biological control

• Severe strawberry root rot observed in Shandong Province, China. • The root rot pathogen of strawberry was identified as Fusarium citri . • This is the first report of F. citri as a causal agent of root rot on strawberries. • The antagonistic effect and pot efficacy of Streptomyces rhizosphaericus were tested. Strawberry root rot is a worldwide challenge in plantations, inflicting significant economic losses. Among the causative agents, Fusarium spp. are major pathogens that trigger root rot and wilt in strawberry and other cash crops. In March 2023, an outbreak of root rot occurred in strawberry fields of Zibo city, Shandong province, China. Infected plants exhibited severe symptoms, including high mortality, root necrosis, lack of fresh root growth, crown discoloration, and leaf withering. To identify the pathogen, morphological observation and phylogenetic analysis of multiple gene regions (ITS, CAM , EF , RPB2 , and TEF ) were conducted. The results confirmed that Fusarium citri was the causal agent of the root rot. Pathogenicity tests and Koch’s postulates further demonstrated that F. citri isolates induced symptoms consistent with those observed in the field. Notably, this study represents the first report of F. citri inducing root rot on strawberry in China. Application of Streptomyces rhizosphaericus in both in vitro and in plant pathogen challenge experiments revealed a potential for this organism as biological control agent for the management of strawberry root rot caused by F. citri .