Abstract
Crossing experiments were conducted among three isolates of Bursaphelenchus xylophilus and eight isolates of B. mucronatus from wide geographical sources in Japan. Crossing between isolates of the same species produced fertile hybrids in every case. In all crossing combinations between B. xylophilus and B. mucronatus, F1 progenies were produced. However, the number of produced hybrids were limited and some of them were aberrant. These F1 hybrids failed to produce the F2 generation. Back crossing of F1 hybrids to their parent adults also failed to achieve progeny production. These results are indicative of a valid separation of B. mucronatus from B. xylophilus, although they are closely related.
