Effects of inter-specific crossbreeding between the invasive pine wood nematode, Bursaphelenchus xylophilus and native B. mucronatus on morphology and reproduction of the hybrid offspring.
The process of inter-specific hybridization between the invasive, highly pathogenic pinewood nematode, Bursaphelenchus xylophilus and the Eurasian-native, relatively harmless B. mucronatus has been examined with the aid of the B. xylophilus Roller (Bxy)rol(tom3) mutation (Tomalak & Filipiak, 2019) as a morphological marker, in the breeding protocol. Validity of the morphologically based selection of the inter-specific hybrids has been confirmed by examination of individual nematodes with the multiplex PCR technique with specific primers (Filipiak et al., 2017). The research showed that hybridization between both species was possible in F1 and to some extent in subsequent offspring generations. In the general body plan, the hybrids resembled the wild-type parental species but differed in various morphological/anatomical details. The changes ranged from seemingly indistinct to heavily distorted or occasional missing of particular structures. The most affected were spicules, female tails, the development of gonads and the position of the excretory pore. The hybridization led to various distortions of mating, gametogenesis, embryogenesis and juvenile viability, and development in F1, F2 and subsequent generation offspring, which severely affected the nematode reproductive potential. Potential consequences of the spontaneous inter-specific hybridization between both species are discussed.