Analyses of DNA sequences from the internal transcribed spacer (ITS) region of the nuclear rDNA and from a portion of a manganese-dependent peroxidase gene were used to assess the species in Amylostereum, including isolates from the mycangia of horntails, decay, and basidiomes. Four species are recognized: A. areolatum, A. chailletii, A. laevigatum, and A. ferreum. An unidentified Amylostereum isolate from the mycangium of Xoanon matsumurae had an ITS sequence identical to that of A. areolatum. Another unidentified Amylostereum isolate from the mycangium of Sirex areolatus was near A. laevigatum, which appears to be the mycangial symbiont for those horntails attacking cedar-like trees. The other horntail isolates, primarily from Pinaceae, proved to be either A. areolatum or A. chailletii. The DNA sequences of Echinodontium tinctorium, E. tsugicola and E. japonicum were similar to those of the Amylostereum species, and Amylostereum species are now recognized as members of the family Echinodontiaceae rather than the family Stereaceae. Echinodontium taxodii was found to be distinct from the Echinodontiaceae and Stereum, and E. taxodii is recognized as a Laurilia species.
The fungus associated with the Japanese horntail, Urocerus japonicus, in Kochi, Kagawa and Ehime Prefectures was studied. Cultures isolated from the mycangia of 113 adult females of the horntail showed the same cultural characteristics. Four of basidiocarps found on felled logs of Cryptomeriajaponica were identified as Amylostereum laevigatum based on morphological characteristics. This was the first record of A. laevigatum from Japan. The cultures isolated from the basidiocarps had the same cultural characteristics as those from the mycangia of U.japonicus. One mycangial isolate produced basidiocarps on artificially inoculated stem segments of Cr. japonica after a 6-too incubation and was identified as A. laevigatum. One isolate from the basidiocarps of A. laevigatum and one from the mycangium of U. japonicus were artificially inoculated into five trees each of Chamaecyparis obtusa and Cr. japonica. The wood of all inoculated trees showed discoloration, with no difference in shape and pattern of discoloration between the two isolates. The inoculated fungi were reisolated from the areas of discoloration in the inoculated trees.
Deladenus nitobein. sp., a parasite of a woodwasp species,Sirex nitobei, is described based on its typological characters and molecular profiles of part of the small subunit D2-D3 expansion segments of the large subunit and internal transcribed spacer region of the ribosomal RNA gene, as well as part of the mitochondrial cytochrome oxidase subunit I (mtCOI) gene. Adult host woodwasps emerging from dead Japanese red pine logs,Pinus densiflora, collected at Aomori, Japan, were dissected and examined for nematode association. The new species was isolated from the body cavity and reproductive system ofS. nitobeias large parasitic females and small parasitic juveniles. The nematodes were cultured successfully on 1.0% malt extract agar medium, inoculated withSirex-associated fungus,Amylostereumareolatum. The mycophagous adult nematodes were characterised by the relative position of the excretory pore, located at 25 (19-28) and 25 (18-30)μm anterior to the hemizonid in the male and female, respectively, and a broad female tail with a rounded distal end. Typologically, the new species forms a cryptic species complex withD. siricidicolaandD. canii. In addition, the new species andD. siricidicolashare the same host wasp, tree and fungal species in Japan. However, the cryptic species can be separated from each other based on the described morphological and molecular sequence differences in the mtCOI gene.
A fungus associated with a horntail, Urocerus antennatus, in Ibaraki, Kochi, and Nagasaki Prefectures, was studied. Cultures isolated from the mycangia of 12 adult females of U. antennatus showed the same cultural characteristics as those of Amylostereum laevigatum. One mycangial isolate produced basidiocarps on the stem segments of Cryptomeria japonica by artificial inoculation and was identified as A. laevigatum. These results indicate that only A. laevigatum is carried in the mycangia of U. antennatus in Ibaraki, Kochi, and Nagasaki Prefectures.
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