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.
