Showing papers on "Mycovirus published in 1997"
TL;DR: It is concluded that the exclusion of viruses from sexual Aspergilli could be due to the formation of new somatic incompatibility groups by sexual recombination.
Abstract: Viruses are common in asexual Aspergilli but not in sexual Aspergilli. We found no viruses in 112 isolates of the sexual Aspergillus nidulans. We have investigated factors that could play a role in preventing the spread of mycoviruses through populations of A. nidulans. Experiments were performed with A. nidulans strains infected with viruses originating from A. niger. Horizontal virus transmission was restricted but not prevented by somatic incompatibility. Viruses were transmitted vertically via conidiospores but not via ascospores. Competition experiments revealed no effect of virus infection on host fitness. Outcrossing was found to limit the spread of viruses significantly more than selfing. It is concluded that the exclusion of viruses from sexual Aspergilli could be due to the formation of new somatic incompatibility groups by sexual recombination.
70 citations
TL;DR: It is shown that somatic compatibility between different strains is exceptional in natural populations of the asexual black Aspergilli, and horizontal transfer of mycoviruses only occurs between the (very rare) compatible combinations of strains.
Abstract: The extent of heterokaryon (also termed somatic or vegetative) incompatibility among black Aspergillus strains was examined using nitrate non-utilising mutants selected on chlorate medium. Pairings of complementary mutants showed that somatic compatibility between different strains is exceptional in natural populations of the asexual black Aspergilli. Mycoviruses are present in a considerable fraction of the sampled natural population, but surprisingly, horizontal transfer of mycoviruses only occurs-at least under laboratory conditions-between the (very rare) compatible combinations of strains. Thus, unlike other fungal species, somatic incompatibility in black Aspergilli efficiently blocks virus transfer. Viruses present in black Aspergillus isolates are highly efficiently transmitted to asexual progeny.
65 citations
TL;DR: It was observed that only the L-double-stranded RNA molecule copurified with isometric virus-like particles that had a similar morphology and size as those detected by electron microscopy in the mycelium sections.
Abstract: In wild-type Botrytis cinerea CVg25 strain we have detected the presence of extrachromosomal genetic elements corresponding to double-stranded RNA molecules. These genetic elements have been designated L, M1 and M2 with molecular sizes of 8.3, 2.0 and 1.4 kb, respectively. The visualization by electron microscopy of mycelium ultrathin sections from B. cinerea CVg25 showed the presence of isometric virus-like particles of about 40 nm in diameter. Linear sucrose gradient centrifugation of mycelium-free extracts was done to determine if the double-stranded RNAs were associated with virus-like particles. The gradient profile obtained at 260 and 280 nm revealed a major peak that was analyzed by both agarose-gel electrophoresis and electron microscopy. It was observed that only the L-double-stranded RNA molecule copurified with isometric virus-like particles. These virus-like particles had a similar morphology and size as those detected by electron microscopy in the mycelium sections. These results suggest that only the L-double-stranded RNA would be encapsidated.
33 citations