Abstract
A pink isolate (QT5-19) of Botrytis cinerea was compared with three gray isolates of B. cinerea for growth and morphogenesis on potato dextrose agar (PDA), and for pathogenicity on tobacco. A double-stranded (ds) RNA mycovirus infecting QT5-19 was identified based on its genome feature and morphology of the virus particles. The results showed that QT5-19 grew rapidly and established flourishing colonies as the gray isolates did. However, it is different from the gray isolates, as it failed to produce conidia and sclerotia asthe gray isolates did. QT5-19 hardly infected tobacco, whereas the gray isolates aggressively infected tobacco. Two dsRNAs were detected in QT5-19, dsRNA 1 and dsRNA 2, were deduced to encode two polypepetides with homology to viral RNA-dependent RNA polymerase (RdRp) and coat protein (CP), respectively. Phylogenetic analysis of the amino acid sequences of RdRp and CP indicated that the two dsRNAs represent the genome of a novel partitivirus in the genus Alphapartitivirus, designated here as Botrytis cinerea partitivirus 2 (BcPV2). BcPV2 in QT5-19 was successfully transmitted to the three gray isolates through hyphal contact. The resulting BcPV2-infected derivatives showed rapid growth on PDA with defects in conidiogenesis and sclerogenesis, and hypovirulence on tobacco. This study suggests that BcPV2 is closely associated with hypovirulence of B. cinerea.
Highlights
Mycoviruses are viruses infecting filamentous fungi, yeasts, and oomycetes [1,2,3].Previous studies demonstrated that mycoviruses widely exist in all major taxonomic groups of fungi and oomycetes [4]
The results showed that Botrytis cinerea partitivirus 2 (BcPV2) belongs to the genus Alphapartitivirus (Figure 7A,B)
QT5-19 of B. cinerea is a hypovirulent on apple, cucumber, oilseed rape, that strawberry, grapes, tobacco, and tomato, compared toisolate the gray apple, cucumber, oilseed rape, strawberry, table grapes, tobacco, and tomato, compared to the gray isolates
Summary
Mycoviruses (or fungal viruses) are viruses infecting filamentous fungi, yeasts, and oomycetes [1,2,3].Previous studies demonstrated that mycoviruses widely exist in all major taxonomic groups of fungi and oomycetes [4]. Most mycoviruses have the genomes of RNA, either double-stranded RNA (dsRNA). Single-stranded RNA (ssRNA), whereas a few mycoviruses have the genomes of single-stranded. The mycoviruses in the families Chrysoviridae, Megabirnaviridae, Patitiviridae, Reoviridae, and Totiviridae have the dsRNA genomes, which are encapsidated within the coat proteins (CP), thereby forming virus particles. The mycoviruses in the other families such as Hypoviridae and Narnaviridae have the positive ssRNA (+ssRNA) genomes, which are unencapsidated without formation of virus particles [6,7]. A few mycoviruses with the genomes of negative ssRNA (−ssRNA) have been identified in a few plant pathogenic fungi, including Botrytis cinerea [8,9], Erysiphe pisi [10], Fusarium graminearum [11], and Sclerotinia sclerotiorum [12]
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