Biology of Ascobotryozyma americana and identification of other fungi associated with wood-boring beetles in Populus and Salix.

摘要

Collections were made from beetle-damaged tissues in Populus and Salix in eastern Washington and western Idaho, U.S.A. in search of Botryozyma, a unique nematode-associated asexual yeast. The type species, B. nematodophila, was discovered in Verona, Italy from nematodes (Panagrellus redivivoides) associated with sour-rot of grapes. Botryozyma was a monotypic genus until a second species, B. americana, was discovered on the surface of nematodes associated with beetle galleries in Populus tremuloides in Washington by Jack D. Rogers. Sampling yielded twenty-one isolates from nine locations, including the discovery of the sexual state (teleomorph) of B. americana. All isolates were found attached to Panagrellus dubius nematodes, and the beetles were confirmed to be Saperda calcarata and Cryptorhynchus lapathi in Populus and Salix, respectively. A new genus, Ascobotryozyma, was erected to accommodate the teleomorph, characterized by its globose asci bearing four lunate ascospores, formed on thallus cells after the fusion of two or more thalli. Isolates from Washington are described as a new species, A. americana, based on the teleomorph. Ascobotryozyma americana differs from B. nematodophila in its distribution, nematode host, habit, morphology, physiological and molecular characteristics, and the production of the teleomorph. Additional investigations, including DNA fingerprinting and sequence comparisons, revealed isolates from Idaho, collected from both Populus and Salix, represent an additional taxon of Ascobotryozyma. Ascobotryozyma (Botryozyma) was shown to have a commensal relationship with nematodes. The specificity of attachment to nematode taxa, the developmental morphology of cell-by-cell thallus growth, and the ultrastructure of thallus cells and asci of different ages are also presented. To gain a better understanding of the fungi associated with these beetles, collections were made from S. calcarata galleries in P. tremuloides approximately every six weeks for twenty-seven months. As a comparison, fungi from C. lapathi galleries in Salix from which Ascobotryozyma was found were also identified. A total of fifty-six taxa from forty-one genera were identified, and forty-two of the more common or distinctive taxa are described and illustrated.