Conidial formation and pathogenicity of Ciboria shiraiana

ObjectiveTo provide a basis for controlling hypertrophy sorosis scleroteniosis, the biological characteristics, the method to induce conidia through mycelia and production pathway of Ciboria shiraiana were studied. MethodsWe observed the morphological characters of conidia in diseased mulberry fruit and artificial culture under microscope. The effects of different temperature and humidity on conidial production by hyphae were determined; the healthy mulberry fruit was inoculated with the conidial suspension in diseased mulberry fruit and artificially induced, and the incidence rate was counted. Also, we used different pathogenic stages of diseased mulberry fruit, mycelium and sclerotium on the PDA medium or induction medium as materials, and the expression level of related genes was detected by qPCR method to reveal the effect of the cAMP pathway on conidial formation. ResultsC. shiraiana produced abundant conidia in artificial cultures at 20-30℃ with 50%-80% relative humidity. The morphology of conidia produced by artificial induction was greatly different from that in diseased mulberry fruits. The conidia suspension in the diseased mulberry fruit infected healthy mulberry, the incidence rate was 37%, and the artificially induced conidia had no infectivity to mulberry. Conidiophores and conidia could be induced using potato slices as the artificial culture medium. Exogenously added cAMP affected the morphology of mycelium and the formation of conidial, but didn't affect the formation of sclerotia. A qPCR analysis showed that the relative transcript levels of adenylate cyclase (AC) content increased rapidly in the second stage, decreased rapidly in the third and fourth stage, and PKA was not expressed in diseased mulberry fruit. ConclusionDiseased mulberry fruits of hypertrophy sorosis scleroteniosis can be re-infected by conidia. Conidia formation negatively regulates the expression of AC and PKA in the cAMP pathway. The results of this study can further enhance our understanding of the environmental conditions required for pathogen to infect mulberry fruits, and further improve the infection cycle and conidial formation pathway of C. shiraiana.