USE OF SPECIES-SPECIFIC SATELLITE DNA FROM BURSAPHELENCHUS-XYLOPHILUS AS A DIAGNOSTIC PROBE

We describe the development of a species-specific DNA probe with the satellite DNA (satDNA) isolated from the Japanese J10 isolate of Bursaphelenchus xylophilus. We show that this MspI satDNA probe is effective directly on a single squashed nematode spotted onto a filter. Therefore, in the pinewood nematode species complex, the identification of the plant pathogenic species B. xylophilus may be accomplished both rapidly and reliably. We also show that the MspI satellite sequence is polymorphic within B. xylophilus species. Hybridization patterns of B. xylophilus isolates with the MspI satellite probe result in very different profiles, with polymorphisms characterizing each of the tested strains. The most important polymorphism, involving mainly qualitative differences, was observed in the hybridization ladder from 1.6 kb upward. Furthermore, the American and Japanese isolates hybridized more strongly to the probe than did the Canadian isolates. Therefore, Japanese isolates of B. xylophilus seem to be closer to the American than to the Canadian isolates. This result agrees with those previously obtained with other DNA probes. This observation supports the hypothesis that a B. xylophilus isolate reached Japan from North America, probably from the United States.