Fungal diseases of eucalypts in China

Abstract

The eucalypt industry in China is expanding substantially, while information on the species identity, origin and impact of fungal pathogens in the country remains very limited. Studies presented in this dissertation investigated some of the most common disease problems experienced in eucalypt plantations in South China during 2006–2008. The causal agents of five common eucalypt diseases were characterized using morphology and DNA sequence data. Furtheremore, the population diversity and structure of Teratosphaeria zuluensis was investigated using microsattelite markers. Species in two genera of Cryphonectriaceae, Chrysoporthe and Celoporthe, species in the Botryosphaeriaceae, Calonectria spp. and T. zuluensis were identified as pathogens to eucalypts in South China. Although the origin of most of these pathogens remains unclear, it is highly likely that some of them originated from native trees in Asia and have adapted to non-native plantation grown eucalypts. They are now causing diseases on these trees as a result of a lack of natural resistance through co-evolution. For example T. zuluensis was found to have a very high genetic diversity in China, and unlike other population studies, suggesting the presence of sexual recombination in the region. Additionally, pathogenicity trials were conducted to screen various commercially grown eucalypt genotypes for their susceptibility to the identified pathogens. These inoculation studies highlighted the importance of knowledge regarding the pathogen genotypes present in a region, and especially the importance of isolate selection when considering artificial screening for disease tolerance. Research presented in this dissertation represents the most detailed investigation of eucalypt fungal diseases in China to date. Clearly, the number of disease and pest problems on plantation eucalypts in China is, and will continue to grow. This is especially true because of the increased movement of forestry material in the form of seed, timber and other products between regions, countries and continents. A combination of management strategies as well as close interaction between foresters, tree breeders and pathologists/entomologists will be needed to ensure a sustainable Eucalyptus forestry industry in China.