Genome characterization of a divergent isolate of the mycovirus Botrytis virus F from a grapevine metagenome.

As part of a grapevine metagenome study, total RNA extracted from grapevine phloem scrapings was analyzed by Illumina sequencing. For one 420A rootstock sample, reads mapping against a reference database and BLAST annotation of contigs identified the presence of a divergent isolate of Botrytis virus F (BVF). The full genome sequence of this isolate (IVC-5-77) was determined (6,828 nucleotides [nt], excluding the poly(A) tail) and shown to be collinear with that of the BVF reference isolate, with the two open reading frames encoding a replication-associated protein (REP) and a coat protein (CP). The IVC-5-77 isolate, however, is very divergent, showing only 81.3-81.6% nucleotide sequence identity to the two other sequenced BVF isolates. The internal non-coding region was also found to be highly variable between BVF isolates. Analysis of the RNASeq reads demonstrated that close to 20% of them belong to Botrytis cinerea, the putative host of the IVC-5-77 isolate. These results extend our knowledge of the diversity and variability of BVF and demonstrate its detectability, together with that of its B. cinerea host, in total RNA RNASeq data from grapevine phloem scrapings.