First field isolation of wound tumor virus from a plant host: minimal sequence divergence from the type strain isolated from an insect vector.

A new strain of wound tumor virus (WTV) has been isolated from a periwinkle plant (Catharanthus roseus) that was among several used as bait plants in a blueberry field. The 12 segments of double-stranded RNA of the viral genome were isolated directly from infected tissue and found to have mobilities through agarose gels that were identical to those of the type strain WTV. Coupled complementary DNA (cDNA) and polymerase chain reactions (PCR) primed with oligonucleotides complementary to the termini of segments 4-12 of the type strain of WTV successfully amplified those segments. Amplification products of the 9 segments were of the size expected for the full-length segment, with no shorter than full-length products representing defective RNAs detected. PCR products representing segments 7, 11, and 12 were cloned and sequenced in their entirety. The sequence of each segment varied only slightly from the homologous segment of the type strain. Variation ranged from less than 1% for segment 12 to approximately 3% for segment 7, but even these low levels of variation were much greater than the variation found in WTV isolates maintained in the laboratory. Most of the variation in each of the three segments was confined to the coding regions, and most of the differences were third position transitions. The new WTV strain has been designated WTVNJ.