Ophiostomatoid fungi (Ascomycota) associated with Pinus tabuliformis infested by Dendroctonus valens (Coleoptera) in northern China and an assessment of their pathogenicity on mature trees

Abstract

Dendroctonus valens is an invasive pest in coniferous forests of northern China. It was suspected of being responsible for the death of more than three million Pinus tabuliformis trees. The present study sought to identify the ophiostomatoid fungi associated with D. valens in northern China and understand the possible role of these fungi in the pine decline. On the basis of morphology, physiology, mating compatibility and phylogenetic analyses of multiple DNA sequences, seven species of ophiostomatoid fungi were isolated from and around D. valens galleries: Leptographium alethinum, Grosmannia koreana (teleomorph of L. koreanum), L. procerum, L. sinoprocerum, L. truncatum, Pesotum aureum and P. pini. All have been recorded for the first time in China. Among them, the occurrence of the dominant species L. procerum is positively linked to attack intensities of D. valens. The pathogenicity of four species (L. koreanum, L. procerum, L. sinoprocerum and L. truncatum) was tested on mature P. tabuliformis trees by stem inoculation. All inoculated strains caused significant necrotic lesions on the inner bark. However, L. koreanum and L. truncatum induced more extensive lesions than L. procerum and L. sinoprocerum. Their association with D. valens and the P. tabuliformis decline is discussed.

Taxonomy and phylogeny of the Leptographium procerum complex, including Leptographium sinense sp. nov. and Leptographium longiconidiophorum sp. nov.

“…Pathogenicity has been tested for only L. sinoprocerum residing in the Asian lineages. This species was thought to be less pathogenic than the other fungal associates of D. valens based on the lesions resulting from inoculations in the crowns of mature P. tabuliformis in China (Lu et al 2009b).…”

Phylogeny and taxonomy of species in theGrosmannia serpenscomplex

“…In an extensive survey of ophiostomatoid fungi on P. densiflora its many bark beetle associates and their galleries L. yamaokae was isolated from only 10 of 20 Hylastes plumbeus galleries and from two of 48 beetles of this species (Masuya et al 2009 China (Lu et al 2009a, 2009b, Paciura et al 2010. Considering the absence of this species from these studies in the Far East and the large number of beetle species investigated by Masuya et al (2009), the association between L. yamaokae and H. plumbeus could be quite specific.…”

Anthropogenic effects on interaction outcomes: examples from insect-microbial symbioses in forest and savanna ecosystems

“…Isolation studies revealed at least ten species of ophiostomatoid fungi including several from North America, as well as at least one strain from Europe (Q. Lu et al 2008;Lu et al 2009a). The rest were apparently acquired by the beetle in China.…”

“…At this point, evidence indicates that the fungi alone are not responsible for the aggressiveness of this beetle in China. Rather, it is likely due to a combination of the fungi, a lack of coevolved resistance in the host tree, and drought stress (Lu et al 2009a).…”