Is Bursaphelenchus mucronatus a weak pathogen to the Japanese red pine?

Abstract

AbstractThe pine wood nematode, Bursaphelenchus xylophilus, is the causal agent of pine wilt disease. It can invade healthy pine trees through the feeding wound of its vector beetle, Monochamus alternatus, and can enter a dead or dying tree through the vector's oviposition mark. By contrast, B. mucronatus, which is closely related to B. xylophilus but has been considered to have no pathogenicity to pine species, also invades living host trees through the same process as B. xylophilus, although the transmission efficiency is lower than that of B. xylophilus. In order to clarify the reason why Bursaphelenchus mucronatus invades a living host, we inoculated shaded and unshaded host seedlings of Pinus densiflora with B. mucronatus. Bursaphelenchus mucronatus displayed pathogenicity in the host seedlings but only with those that were shaded. In addition, B. mucronatus was recovered from the seedlings that had survived until the end of the experiment. Bursaphelenchus mucronatus seems to survive in the living healthy host tree without causing disease symptoms. These results suggest a mutualistic relationship between B. mucronatus and its vector beetle.