Abstract
Botrytis cinerea is a ubiquitous plant pathogenic fungus, causing gray mold disease on many economically important crops, including apple. The present investigation was carried out to characterize a hypovirulent strain AppleBc.07 of B. cinerea collected from an apple orchard located in Yantai City, Shandong Province, China. A comparison with the reference strain of B. cinerea B05.10 suggested that the isolated strain AppleBc.07 was B. cinerea consisting of gray-white, circular, fluffy pattern mycelia and black sclerotia. BLASTn analysis showed that the sequences of internal transcribed spacers (ITS), glyceraldehyde-3-phosphate dehydrogenase (G3PDH), heat-shock protein 60 (HSP60), and DNA-dependent RNA polymerase subunit II (RPB2) were 99-100% identical to the corresponding sequences of other B. cinerea strains, and the phylogenetic analysis based on concatenated G3PDH, HSP60, and RPB2 sequences also indicated that strain AppleBc.07 was clustered with reference strains of B. cinerea. Moreover, it was also found that the strain AppleBc.07 rarely infect apples, tomato, rapeseed, and pepper, whereas the reference strain B05.10 isolates aggressively infect those. Interestingly, no viral dsRNA was speculated in AppleBc.07 strain, postulated that it was a hypovirulent strain, which might be responsible to reduce production of laccase and the limited number of infection cushion (IC) formation. Furthermore, the IC formation genes (Bciqg1, Bcmsb2, and Bcsac1) in AppleBc07 showed alternative expression that could be another possible reason behind this hypovirulence. To the best of our knowledge, this is the first report of a natural occurrence of a hypovirulent B. cinerea strain from apple in China.