Ophiostomatoid fungi associated with pines infected by Bursaphelenchus xylophilus and Monochamus alternatus in China, including three new species

Abstract

The activity of the pine wood nematode Bursaphelenchus xylophilus leads to extremely serious economic, ecological and social losses in East Asia. The nematode causes pine wilt disease, which is currently regarded as the most important forest disease in China. The pathogenic nematode feeds on dendrocola fungi to complete its cycle of infection. As the vector of the nematode, the Japanese pine sawyer (Monochamus alternatus) also carries dendrocola fungi. Pine woods, infected by B. xylophilus and tunnelled by M. alternatus, are also inhabited by ophiostomatoid fungi. These fungi are well known for their association with many bark and ambrosia beetles. They can cause sapstain and other serious tree diseases. The aims of our study were to investigate and identify the ophiostomatoid communities associated with the epidemic pine wood nematode and the pine sawyer in Pinus massoniana and P. thunbergii forests, which are the main hosts of the pine wood nematode in China. Two hundred and forty strains of ophiostomatoid fungi were isolated from nematode and sawyer–infected trees in the coastal Shandong and Zhejiang Provinces, representing newly and historically infected areas, respectively. Six ophiostomatoid species were identified on the basis of morphological, physiological and molecular data. For the latter, DNA sequences of the internal transcribed spacer (ITS1–5.8S–ITS2) region and partial b-tubulin gene were examined. The ophiostomatoid species included one known species, Ophiostoma ips, three novel species, viz. Ophiostoma album sp. nov., Ophiostoma massoniana sp. nov. and Sporothrix zhejiangensis sp. nov. and two species whose identities are still uncertain, Ophiostoma cf. deltoideosporum and Graphilbum cf. rectangulosporium, due to the paucity of the materials obtained. The ophiostomatoid community was dominated by O. ips. This study revealed that a relatively high species diversity of ophiostomatoid fungi are associated with pine infected by B. xylophilus and M. alternatus in China.