Ophiostomatoid fungi associated with bark beetles in China

Abstract

The Ophiostomatales comprises a diverse group of fungi including plant pathogens, human pathogens and most commonly agents of sapstain in timber. In terms of forestry, those species that cause tree diseases and degrade timber are of greatest concern. These fungi are best known as associates of insects and notably bark beetles that infest timber. The importance of an accurate detection of these fungi and their vectors is thus of critical importance to limit global spread and to reduce losses. Similarities based on the ecology and morphology of species in the Ophiostomatales have complicated the taxonomy and accurate identification of these fungi. The availability of DNA sequence comparisons has contributed substantially to improving this situation and many taxonomic controversies have been resolved in recent years. This is a trend that will continue, but for the present there are many unresolved questions relating to the taxonomy of the Ophiostomatales. The first chapter of this thesis provides a review of the literature relating to the taxonomy and importance of the Ophiostomatales. The focus of this review is particularly on the species known from East and Southeast Asia. This is an area of the world where these fungi are relatively poorly known and it justifies the research chapters in the dissertation dealing with the ophiostomatoid fungi from China. The presence of aggressive bark beetles affecting forestry plantations in China, such as Tomicus yunnanensis and Dendroctonus valens and their associated fungi has raised the awareness their potential phytosanitary importance to native and exotic trees. The focus of this research was to identify Ophiostomatales isolated from bark beetles galleries on conifers in two provinces of China. These fungi were initially separated in two main groups based on their anamorph structures. In chapter two, new reports ofPesotum species with Pesotum anamorph, were recognized by morphological characterization and DNA sequence data comparisons. In addition, a new species of Graphium was identified and described. The Ophiostomatalean species with Leptographium anamorph were studied in chapter three, using morphological and DNA sequence data comparisons and eight new Ophiostomatoid fungi associated with bark beetles in China species were identified and described. The findings of this research have revealed an enormous diversity of Ophiostomatales fungi associated with insects on conifers in Jilin and Yunnan provinces of China. The detection of these fungi is extremely important for the understanding of the diversity and ecology of the ophiostomatoid species and their insect vectors in forest ecosystems in these parts of the world. Copyright