title: DsRNA-free transmissible hypovirulence associated with formation of intra-hyphal hyphae in Botrytis cinerea.
abstract: A spontaneous mutant CanBc-3HV and its parental strain CanBc-3 of Botrytis cinerea were investigated in terms of pathogenicity, colony morphology, hypovirulence transmissibility, presence of double-stranded RNA (dsRNA), and formation of intra-hyphal hyphae (IH). Results showed that inoculation of CanBc-3HV on detached leaves of Brassica napus did not produce any visible necrotic lesions (20°C, 72h), whereas inoculation of CanBc-3 caused necrotic leaf lesions. Compared to CanBc-3, CanBc-3HV grew slowly, formed numerous mycelial sectors, sporulated sporadically and failed to produce sclerotia on potato dextrose agar (PDA) (20°C, 15d). Hypovirulence and the abnormal cultural characteristics of CanBc-3HV were transmissible from CanBc-3HV to CanBc-3 in pair cultures on PDA. However, the transmission was unsuccessful from CanBc-3HV to another virulent strain CanBc-2 of B. cinerea. These results suggest that transmission of the hypovirulence and the abnormal cultural characteristics of CanBc-3HV are strain-specific. No dsRNA was detected in mycelia of either CanBc-3HV or CanBc-3, implying that the hypovirulence of CanBc-3HV is caused by a transmissible element (TE) of non-RNA mycoviral origin. Formation of IH through self-infection was observed in CanBc-3HV, CanBc-3T1 (a hypovirulent derivative of CanBc-3 trans-infected by TE in CanBc-3HV), but was not observed in CanBc-3, suggesting that IH formation is associated with the hypovirulence of CanBc-3HV. To our knowledge, this is the first report of dsRNA-free transmissible hypovirulence associated with IH formation in B. cinerea.
authors: The State Key Laboratory of Agricultural Microbiology and Key Laboratory of Plant Pathology of Hubei Province, Huazhong Agricultural University, Wuhan 430070, Hubei, China; Electron microscopes Laboratory, Huazhong Agricultural University, Wuhan 430070, China.
authors: Jian Bo
authors: JB
authors: Cao
authors: Yu
authors: Y
authors: Zhou
authors: Lei
authors: L
authors: Zhang
authors: Jing
authors: J
authors: Zhang
authors: Long
authors: L
authors: Yang
authors: Li Hong
authors: LH
authors: Qin
authors: Dao Hong
authors: DH
authors: Jiang
authors: Guo Qing
authors: GQ
authors: Li
authors: Hung-Chang
authors: HC
authors: Huang
mesh_terms: D020171:Botrytis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism / Q000472:pathogenicity*; D029688:Brassica napus / Q000382:microbiology; D004271:DNA, Fungal / Q000235:genetics / Q000378:metabolism*; D025301:Hyphae / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism / Q000472:pathogenicity; D010935:Plant Diseases / Q000382:microbiology*; D012330:RNA, Double-Stranded / Q000235:genetics / Q000378:metabolism*; D014774:Virulence
chemical_list: D004271:DNA, Fungal; D012330:RNA, Double-Stranded