MOLECULAR EVIDENCE THAT STRAIN BV-15 OF PEANUT STUNT CUCUMOVIRUS IS AREASSORTANT BETWEEN SUBGROUP-I AND SUBGROUP-II STRAINS

In Northern hybridization assays, RNA1 of peanut stunt virus (PSV) str ain BV-15 hybridized strongly with a cloned cDNA probe to RNA1 from st rain PSV-W (subgroup II). Cloned probes to PSV-W RNA2 and RNA3, howeve r, did not hybridize with the corresponding RNAs from strain BV-15. Th e complete nucleotide sequence of PSV-BV-15 RNA2 has been determined, and sequence comparison analysis showed that it is closely related to PSV subgroup I strains; the percent nucleotide sequence identity betwe en PSV-BV-15 RNA2 and RNA2 sequences from PSV subgroup I and II strain s were 90.5 and 75%, respectively. The possibility that PSV-BV-15 RNA2 may contain short regions derived from a subgroup II strain (i.e., re present a mosaic structure indicative of recombination) was investigat ed. Results indicated, however, that the entire PSV-BV-15 RNA2 sequenc e is derived from a subgroup I strain. PSV-BV-15 RNA3 has previously b een shown to belong to subgroup I strains. These results thus establis h that PSV strain BV-15 is a natural reassortant between PSV subgroups I and II strains. A reverse transcription-polymerase chain reaction a ssay is proposed for differentiating between this reassortant strain a nd PSV strains in subgroups I and II.