Abstract:

Objective: This study isolated and identified the pathogen causing canker disease of Toona sinensis in Zhejiang Province, to reveal the etiology of the disease and provide a theoretical basis for controlling Chinese toon canker disease. Method: The symptoms of T. sinensis canker disease under natural conditions were observed. The conventional tissue isolation approach was used to isolate the causal pathogen from infected tissues. The morphological traits and molecular methods were used to identify the pathogen species. The pathogenicity of the isolates was verified according to Koch’s postulates. Result: 1) Two strains of pathogenic fungi were isolated from the infected tissues of T. sinensis, XCKY1 and XCKY2. The culture and morphological characteristics of the teleomorph and anamorph of the pathogen were consistent with those of Nectria pseudotrichia. 2) The LSU rDNA, ITS rDNA, and tef1-α gene fragments of the XCKY2 strain were all 100.00% homologous to those of N. pseudotrichia. The XCKY1 and XCKY2 strains clustered with 11 N. pseudotrichia strains with a Bayesian posterior probability of 0.94. 3) The pathogenicity test result showed that both fungal agar plugs and conidial suspensions of N. pseudotrichia caused necrotic lesions on healthy T. sinensis seedlings, and N. pseudotrichia was re-isolated from the necrotic tissue. Thus, it was confirmed that N. pseudotrichia is the causal agent of T. sinensis canker disease. Conclusion: Two strains of N. pseudotrichia isolated from infected tissues of T. sinensis in Zhejiang Province have been identified as the pathogen causing Chinese toon canker disease. This is the first report of N. pseudotrichia causing canker disease in T. sinensis.

Key words: Toona sinensis, canker disease, pathogenic fungi, pathogenicity, phylogenetic analysis, Koch’s postulates