Nematicidal effect of Sparassis latifolia-derived sparassol and disodium sparassol against Bursaphelenchus xylophilus

Abstract

The pine wood nematode (Bursaphelenchus xylophilus) causes pine wilt disease, which is a major problem affecting pine forests. This study aimed to identify metabolites from Sparassis latifolia that have nematicidal activity and to investigate the effect of water-soluble formulations of the active compounds for use as trunk-injectable control agents against the nematode B. xylophilus. When the submerged cultures of S. latifolia were bioassayed against B. xylophilus, strain KFRI 747 showed the most potent activity (52.8%), followed by KFRI 1080 (44.4%) and KFRI 645 (34.8%); their activities were correlated with the concentration of sparassol in their mycelia. Six fractions (SLE1-6) were obtained from ethyl acetate extracts of the liquid culture medium; nematicidal activity was found only in SLE4 (which included sparassol). Sparassol bioassayed against B. xylophilus and had LC50 and LC95 of 84.92 and 132.13ppm, respectively. Sparassol was modified to disodium sparassol using NaOH because sparassol was not water-soluble and thus was not useful as an agent for trunk injection. Disodium sparassol exhibited similar nematicidal activity to that found with sparassol. The trunk-injectable nematicides (abamectin and emamectin benzoate) were more effective than sparassol and disodium sparassol in terms of LC50 and LC95 values. However, sparassol has a more simple chemical structure than these compounds and could be more easily synthesized. To our knowledge, this is the first report indicating that disodium sparassol might be useful as nematicide for use against the pine wood nematode.