RT-PCR for detecting five distinct Tospovirus species using degenerate primers and dsRNA template

RT-PCR procedures for detection of multiple species of tospovirus from plant tissues were investigated. Downstream primers were designated from the 3' untranslated sequences of the S RNA. An upstream primer was designated from the degenerated sequences of the nucleocapsid protein. Approximately 450 bp DNA fragments were detected when Tomato spotted wilt virus (TSWV)- or Impatiens necrotic spot virus (INSV)- infected tissues were examined. Approximately 350 bp DNA fragments were detected when Watermelon silver mottle virus (WSMoV)- or Melon yellow spot virus (MYSV)-infected tissues were examined. Template RNA was extracted using CF 11 cellulose powder, and nonspecific amplification became unnoticeable when double-stranded RNA was used. The amplified fragments of WSMoV were differentiated from those of MYSV by AluI or TaqI digestion. The amplified fragments of TSWV were differentiated from those of INSV by DraI or HindIII digestion. An alstroemeria plant that was infected with an unidentified tospovirus was also examined, and a 350 bp fragment that was 97% identical to Iris yellow spot virus was detected. This method, therefore, detected at least five distinct Tospovirus species.