Chemical Defense Responses of Wilt-Resistant Pine Species, Pinus strobus and P. taeda, against Bursaphelenchus xylophilus Infection.

Abstract

Bursaphelenchus xylophilus was inoculated into the branch of wilt-resistant Pinus taeda and P. strobus, and susceptible P. thunbergii. Ethanol-extractives from the inoculated branches were investigated for the presence of unique resistance chemicals. Accumulation of antifungal substances were observed both in the cortex/phloem and xylem of P. strobus one week after inoculation. Their activity was maintained during the experiment. Pinosylvin, pinosylvin monomethylether, pinobanksin and pinocembrin were identified among the inhibitory substances extracted from the P. strobus xylem. These substances are thought to immobilize B. xylophilus. Only slight inhibitory activity to the fungus but not to the nematode was detectable in P. taeda and P. tunbergii 5 weeks after inoculation. This suggests that ethanol-soluble inhibitory substances are produced in the resistance responses of inoculated branches of P. strobus against B. xylophilus infection, but not of P. taeda.