Pathogenicity and boarding ability of hybrid-derived populations between Bursaphelenchus xylophilus and B. mucronatus (Nematoda: Aphelenchoididae)

What is it about?

The pinewood nematode (Bursaphelenchus xylophilus) is a tiny worm and causes pine wilt disease. It is native to North America and has been devastating pine forests in East Asia and West Europe since the introduction. Long-horned beetle adults transmit the pathogenic nematode from diseased to healthy trees. A closely related, non-pathogenic nematode (Bursaphelenchus mucronatus) is widely distributed in Eurasia. If hybrids between the two species are backcrossed with B. xylophilus nematodes repeatedly, a small proportion of B. mucronatus genes would be infused into B. xylophilus genome (introgression) and may lead to adaptation to locally harsh environments. Inoculation tests revealed that two of eight hybrid-derived populations caused pine seedling mortalities of 36-70 %. The pathogenic hybrid-derived populations carried nuclear DNA marker (ribosomal DNA) of two species and B. xylophilus extranuclear genes whereas non-pathogenic populations carried B. mucronatus DNA marker and extranuclear genes of B. xylophilus or B. mucronatus. Thus, it is inferred that a gene or genes associated with pathogenicity are present in the nuclear genome of B. xylophilus. A laboratory experiment revealed that a pathogenic hybrid-derived population had as high an ability to board beetle adults as the parental-lineage B. xylophilus. Thus, the introgression hybridisation is considered to occur in pine forests if two species cohabit in host trees.

Featured Image