出版社：Forestry Commission of the Hungarian Academy of Sciences
摘要：Types and races of Gremmeniella abietina species complex cause Scleroderris canker on pine trees in Europe and North America. We have studied viruses of types A and B of Gremmeniella abietina. In type A three different mycoviruses belonging to families totivirus, partitivirus and mitovirus occur. They were even observed to inhabiting a single mycelium. During early analyses of these viruses family partitivirus was the most common one. In more recent sampling partitiviruses and totiviruses were rare, but mitoviruses very common. In type B we observed totiviruses, mitoviruses and a previously uncharacterized virus with high similarity to plant endornaviruses. The difference of viruses in types A and B supports our previous hypothesis that viruses do not move freely between the two Fennoscandian types of G. abietina. A partial sequence, covering about 70 % of the complete genome, of putative totivirus of type B was determined. The dsRNA genome codes for putative coat and putative RNA dependent RNA polymerase (RdRp) and they were most similar to similar proteins of the totiviruses of Spaeropsis sapinea and Helicobasidion momba, respectively. A complete sequence of a mitovirus from type B was determined. The putative RdRp was most similar to RdRp of a mitovirus from Ophiostoma novo-ulmi. The previously sequenced mitoviruses from type A had a relatively dissimilar RdRp. The putative start codon was in an AU-rich region surrounded by regions with a relatively high GC-content. Several previously observed secondary structures could be deduced from the nucleotide sequence, and sequence variations occurred at both ends. The previously uncharacterized virus from type B was completely determined independently from two isolates. The dsRNA molecules (10374 and 10375 nucleotides) encoded for putative polyprotein possessing four conserved motifs coding for viral methyl transferase, DEAD/DEAH box helicase, viral RNA helicase and RdRp. A population structure was determined for type A mitoviruses based on RT-PCR amplification and sequencing. It showed no genetic differentiation between the populations, suggesting that viruses are able to disperse freely between locations in southern Finland
