Abstract
      A novelmycovirus,termedFusariumgraminearumHypovirus2(FgHV2/JS16),isolatedfromaplant pathogenic fungus, Fusarium graminearum strain JS16,wasmolecularlyandbiologicallycharacterized. The genomeofFgHV2/JS16is12,800nucleotides(nts)long,excludingthepoly(A)tail.Thisgenomehas
 nly onelargeputativeopenreadingframe,whichencodesapolyproteincontainingthreenormal functional domains,papain-likeprotease,RNA dependentRNApolymerase,RNAhelicase,andanovel domain withhomologousbacterialSMC(structuralmaintenanceofchromosomes)chromosome segregation proteins.AdefectiveRNAsegmentthatis4553-ntslong,excludingthepoly(A)tail,was also detectedinstrainJS16.Thepolyproteinsharedsignificant aaidentitieswithCryphonectria hypovirus1(CHV1)(16.8%)andCHV2(16.2%).Phylogeneticanalysesbasedonmultiplealignmentsof the polyproteinclearlydividedthemembersof Hypoviridae into twomajorgroups,suggestingthat FgHV2/JS16wasanovelhypovirusofanewlyproposedgenus Alphahypovirus—composed ofthe members ofGroup1,includingCHV1,CHV2,FgHV1andSclerotiniasclerotiorumhypovirus2.FgHV2/ JS16wasshowntobeassociatedwithhypovirulencephenotypesaccordingtocomparisonsofthe biological propertiessharedbetweenFgHV2/JS16 infectedandFgHV2/JS16-freeisogenicstrains. Furthermore,wedemonstratedthatFgHV2/JS16infectionactivatedtheRNAinterferencepathwayin Fusarium graminearum by relativequantitativerealtimeRT-PCR.