RESUMEN
Fusarium head blight (FHB) continues to be a major problem in wheat production and is considered a disease complex caused by several fungal pathogens including Fusarium culmorum, F. graminearum and F. equiseti. With the objective of investigating diversity of mycoviruses in FHB-associated pathogens, we isolated Fusarium spp. from six wheat (Triticum aestivum) cultivars. In total, 56 Fusarium isolates (29 F. culmorum, 24 F. graminearum, one F. equiseti) were screened for mycoviruses by extracting and sequencing double-stranded RNA. We found that a large proportion of Fusarium isolates (46 %) were infected with mycoviruses. F. culmorum, previously described to harbor only one mycovirus, tended to host more viruses than F. graminearum, with a few isolates harboring seven mycoviruses simultaneously. Based on the RNA-dependent RNA polymerase domain analysis, ten were positive-sense single-stranded RNA viruses (related to viruses from families Mitoviridae, Botourmiaviridae, Narnaviridae, Tymoviridae, Gammaflexiviridae, as well as proposed Ambiguiviridae and ormycovirus viral group), one was double-stranded RNA virus (Partitiviridae), and five were negative-sense single-stranded RNA viruses (related to members in the families of Yueviridae, Phenuiviridae, Mymonaviridae, as well as proposed Mycoaspiviridae). Five mycoviruses were shared between F. graminearum and F. culmorum. These results increase our general understanding of mycovirology. To our knowledge, this is the first in-depth report of the mycovirome in F. culmorum and the first report on the diversity of mycoviruses from Danish isolates of FHB-causing fungi in general.
Asunto(s)
Virus Fúngicos , Fusarium , Filogenia , Enfermedades de las Plantas , Virus ARN , ARN Viral , Triticum , Fusarium/virología , Virus Fúngicos/clasificación , Virus Fúngicos/genética , Virus Fúngicos/aislamiento & purificación , Enfermedades de las Plantas/microbiología , Enfermedades de las Plantas/virología , Triticum/microbiología , Triticum/virología , Virus ARN/genética , Virus ARN/clasificación , Virus ARN/aislamiento & purificación , ARN Viral/genética , Genoma ViralRESUMEN
Agaricus bisporus is a commercial mushroom crop susceptible to a disease caused by a complex of viruses known collectively as mushroom virus X (MVX). Symptoms of MVX include bare patches and mushroom cap discolouration (browning) in the fruiting bodies, phenotypes associated with the viruses AbV6 and AbV16, respectively. Limited understanding exists of the localisation and mobilisation of these viruses within the mycelium of A. bisporus. To this end, a non-destructive fluorescence in situ hybridisation (FISH) method was developed for in situ targeting of AbV6 and AbV16 in A. bisporus mycelium. An MVX strain associated with the bare patch disease phenotype revealed predominantly high signal towards the growing edges of cultures when probed for AbV6, with a 'halo-effect' of high signal intensity around putative vacuoles. An MVX strain associated with the browning disease phenotype showed high signal intensities within reticulating networks of hyphae in a highly compartmentalised manner when probed for AbV16. Localisation of the two viruses in MVX-infected cultures appears independent, as both viruses were found in completely discrete areas of the mycelium in differential patterns. FISH detected low level presence of the two viruses, AbV6 and AbV16 in a number of cultures which had tested negative for the viruses by RT-PCR. This suggests that FISH may be more sensitive at detecting viruses at low levels than molecular methods. This study demonstrates that FISH is a powerful tool in the field of mycovirology.