Hypovirulence of the phytopathogenic fungus Botryosphaeria dothidea: association with a coinfecting chrysovirus and a partitivirus.
Botryosphaeria dothidea is an important pathogenic fungus causing fruit rot, leaf and stem ring spots and dieback, stem canker, stem death or stool mortality, and decline of pear trees. Seven double-stranded RNAs (dsRNAs; dsRNAs 1 to 7 with sizes of 3,654, 2,773, 2,597, 2,574, 1,823, 1,623, and 511 bp, respectively) were identified in an isolate of B. dothidea exhibiting attenuated growth and virulence and a sectoring phenotype. Characterization of the dsRNAs revealed that they belong to two dsRNA mycoviruses. The four largest dsRNAs (dsRNAs 1 to 4) are the genomic components of a novel member of the family Chrysoviridae (tentatively designated Botryosphaeria dothidea chrysovirus 1 [BdCV1]), a view supported by the morphology of the virions and phylogenetic analysis of the putative RNA-dependent RNA polymerases (RdRps). Two other dsRNAs (dsRNAs 5 and 6) are the genomic components of a novel member of the family Partitiviridae (tentatively designated Botryosphaeria dothidea partitivirus 1 [BdPV1]), which is placed in a clade distinct from other established partitivirus genera on the basis of the phylogenetic analysis of its RdRp. The smallest dsRNA, dsRNA7, seems to be a noncoding satellite RNA of BdPV1 on the basis of the conservation of its terminal sequences in BdPV1 genomic segments and its cosegregation with BdPV1 after horizontal transmission. This is the first report of a chrysovirus and a partitivirus infecting B. dothidea and of a chrysovirus associated with the hypovirulence of a phytopathogenic fungus.


OBJECTIVE
Our studies identified and characterized two novel mycoviruses, Botryosphaeria dothidea chrysovirus 1 (BdCV1) and Botryosphaeria dothidea partitivirus 1 (BdPV1), associated with the hypovirulence of an important fungus pathogenic to fruit trees. This is the first report of a chrysovirus and a partitivirus infecting B. dothidea and of a chrysovirus associated with the hypovirulence of a phytopathogenic fungus. BdCV1 appears to be a good candidate for the biological control of the serious disease induced by B. dothidea. Additionally, BdPV1 is placed in a clade distinct from the established genera. The BdCV1 capsid has two major structural proteins, and the capsid is distinct from that made up by a single polypeptide of the typical chrysoviruses. BdPV1 is the second partitivirus in which the putative capsid protein shares no significant identity with any mycovirus protein. A small accompanying dsRNA that is presumed to be a noncoding satellite RNA of BdPV1 is the first of its kind reported for a partitivirus.
State Key Laboratory of Agricultural Microbiology, Wuhan, Hubei, People's Republic of China College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China National Indoor Conservation Center of Virus-Free Germplasms of Fruit Crops, Wuhan, Hubei, People's Republic of China Lab of Key Lab of Plant Pathology of Hubei Province, Wuhan, Hubei, People's Republic of China.
LiPing
L
Wang
State Key Laboratory of Agricultural Microbiology, Wuhan, Hubei, People's Republic of China College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China National Indoor Conservation Center of Virus-Free Germplasms of Fruit Crops, Wuhan, Hubei, People's Republic of China Lab of Key Lab of Plant Pathology of Hubei Province, Wuhan, Hubei, People's Republic of China.
JingJing
J
Jiang
State Key Laboratory of Agricultural Microbiology, Wuhan, Hubei, People's Republic of China College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China National Indoor Conservation Center of Virus-Free Germplasms of Fruit Crops, Wuhan, Hubei, People's Republic of China Lab of Key Lab of Plant Pathology of Hubei Province, Wuhan, Hubei, People's Republic of China.
YanFen
Y
Wang
State Key Laboratory of Agricultural Microbiology, Wuhan, Hubei, People's Republic of China College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China National Indoor Conservation Center of Virus-Free Germplasms of Fruit Crops, Wuhan, Hubei, People's Republic of China Lab of Key Lab of Plant Pathology of Hubei Province, Wuhan, Hubei, People's Republic of China.
Ni
N
Hong
State Key Laboratory of Agricultural Microbiology, Wuhan, Hubei, People's Republic of China College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China National Indoor Conservation Center of Virus-Free Germplasms of Fruit Crops, Wuhan, Hubei, People's Republic of China Lab of Key Lab of Plant Pathology of Hubei Province, Wuhan, Hubei, People's Republic of China.
Fangpeng
F
Zhang
State Key Laboratory of Agricultural Microbiology, Wuhan, Hubei, People's Republic of China College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China National Indoor Conservation Center of Virus-Free Germplasms of Fruit Crops, Wuhan, Hubei, People's Republic of China Lab of Key Lab of Plant Pathology of Hubei Province, Wuhan, Hubei, People's Republic of China xuwenxing@mail.hzau.edu.cn gpwang@mail.hzau.edu.cn.
WenXing
W
Xu
State Key Laboratory of Agricultural Microbiology, Wuhan, Hubei, People's Republic of China College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China National Indoor Conservation Center of Virus-Free Germplasms of Fruit Crops, Wuhan, Hubei, People's Republic of China Lab of Key Lab of Plant Pathology of Hubei Province, Wuhan, Hubei, People's Republic of China xuwenxing@mail.hzau.edu.cn gpwang@mail.hzau.edu.cn.
GuoPing
G
Wang
D020171:Botrytis / Q000472:pathogenicity*; D016679:Genome, Viral; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology* / Q000821:virology*; D031989:Pyrus / Q000382:microbiology*; D012328:RNA Viruses / Q000145:classification / Q000302:isolation & purification / Q000472:pathogenicity*; D012330:RNA, Double-Stranded / Q000235:genetics / Q000378:metabolism*; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism; D014774:Virulence
D012330:RNA, Double-Stranded; D012367:RNA, Viral; D014764:Viral Proteins