Genome characterization of a debilitation-associated mitovirus infecting the phytopathogenic fungus Botrytis cinerea

The full-length sequences of Botrytis cinerea mitovirus 1 (BcMV1) and an associated RNA (BcMV1-S) in strain CanBc-1c-78 of Botrytis cinerea were determined. Sequence analysis showed that BcMV1 is 2804 nt long and AU-rich (66.8%). BcMV1 shares 95% nucleotide sequence identity with Ophiostoma novo-ulmi mitovirus 3b (OnuMV3b). However, it is 472 nt longer than OnuMV3b. Mitochondrial codon usage revealed that BcMV1 contains one open reading frame encoding RdRp, which is 96% identical to the RdRp of OnuMV3b. These findings confirm that BcMV1 belongs to the genus Mitovirus and is a strain of OnuMV3b. BcMV1-S is 2171 nt long and derived from BcMV1 through a single internal in-frame deletion of 633 nt, suggesting that it is a defective RNA of BcMV1. BcMV1-S was found to suppress the replication of BcMV1 and to be co-transmissible with BcMV1 through hyphal anastomosis. Its presence, however, did not alleviate the BcMV1-associated debilitation phenotypes of B. cinerea. (C) 2010 Elsevier Inc. All rights reserved.