Find in Library

<i>Sirex noctilio</i> along with its mutualistic fungal symbiont, <i>Amylostereum areolatum</i> (a white rot fungus), is an invasive pest that causes excessive damage to <i>Pinus</i> plantations in Northeast China. In 2015, <i>S. noctilio</i> were found to attack <i>Pinus sylvestris</i> var. <i>mongolica</i>, and often share larval habitat with the native woodwasp, <i>S. nitobei</i>. The objective of this study was to determine the possible origin(s) of the introduced pest complex in China and analyse the genetic diversity between <i>A. areolatum</i> isolated from invasive <i>S. noctilio</i>, native <i>S. nitobei</i> and other woodwasps collected from Europe (native range) and other countries. Phylogenetic analyses were performed using the intergenic spacer (IGS) dataset and the combined 4-locus dataset (the internal transcribed spacer region (ITS), translation elongation factor alpha 1 (<i>tef1</i>), DNA-directed ribosomal polymerase II (<i>RPB2</i>), and mitochondrial small subunit (mtSSU)) of three <i>Amylostereum</i> taxa. The multilocus genotyping of nuclear ribosomal regions and protein coding genes revealed at least three distinct multilocus genotypes (MLGs) of the fungus associated with invasive <i>S. noctilio</i> populations in Northeast China, which may have come from North America or Europe. The IGS region of <i>A. areolatum</i> carried by <i>S. noctilio</i> from China was designated type B1D2. Our results showed a lack of fidelity (the paradigm of obligate fidelity to a single fungus per wasp species) between woodwasp hosts and <i>A. areolatum</i>. We found that the native <i>S. nitobei</i> predominantly carried <i>A. areolatum</i> IGS-D2, but a low percentage of females instead carried <i>A. areolatum</i> IGS-B1D2 (MLG A13), which was presumably due to horizontal transmission from <i>S. noctilio</i>, during the sequential use of the same wood for larval development. The precise identification of the <i>A. areolatum</i> genotypes provides valuable insight into co-evolution between Siricidae and their symbionts, as well as understanding of the geographical origin and history of both <i>Sirex</i> species and their associated fungi.