Stress Physiology and Virulence Characterization of Phomopsis asparagi （Sacc.） Bub6k isolated from Asparagus in Jiangxi Province of China

摘要

Abstract Fungal pathogen of asparagus stem blight was isolated. No significant ge- netic difference was detected among the three strains with 492 bp long ITS1-5.8S- ITS2 sequence. It was then identified through colony growth, conidia morphology, and molecular characterization. The physiological response to oxidation and osmosis stress, and virulence to Asparagus officinalis L. were analyzed. The results showed that the pathogen causing asparagus stem blight for A. officinalis L. in Jiangxi Province is Phomopsis asparagri （Sacc.） Bubok. Under pure culture conditions, the conidia were oval-shaped （a-type）, with colorless single spore and single nucleus, containing 0-2 oil balls. Its vegetative growth rate was higher when cultured on 0.2 x potato dextrose agar （0.2 x PDA） medium than that on oatmeal agar （OA） medium. However, the pycnidia appeared earlier on OA medium than on 0.2 earlier PDA medium. The vegetative growth rate was depressed under oxidation （H202） or osmo- sis （NaCI） stress conditions, and totally inhibited under 7 mmol/L H202 or 2.4 mol/L NaCI. All the strains caused typical pathogenic symptoms to Asparagus officinalis L. at 7 days-post-inoculation （dpi） with conidia.