Infection Process and Pathogenic Mechanism of Phomopsis asparagi, the Asparagus Stem Blight Pathogen
2016
Yang, Ying-Qing | Lan, Bo | Jian, Yan-Li | Chang, Dong-Dong | Zhang, Shun-Liang | Li, Xiang-Min
The infection process was explored by light and electron microscopy techniques, as well as bioassays assessing phytotoxins and cell wall-degrading enzymes. We found that germ tubes of asparagus stem blight fungus were produced at 0-24 h after culture on dextrose agarose medium, and mycelia were formed at 24-48 h. Then, mycelia grew and spread continuously, making incursions into host tissues after 4 days. The conidial fructification began to form after 8 days. Subsequently, pycnidia were produced after about 12 days, with conidia released after about 16 days. Interestingly, through culture, extraction and bioassay of phytotoxin culture filtrates, no overt damage of asparagus tissues was found. As for cell wall-degrading enzymes, PG showed the highest activity, followed by Cx and PMG; PGTE and PMTE displayed the lowest activities. Finally, we demonstrated that permeable reducing sugars and relative electric conductivity in the culture increased after incubation in cell wall-degrading enzyme solutions, in an enzyme concentration dependent manner.
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