Quambalaria species associated with eucalypt diseases in southern China

The genus Quambalaria includes several important pathogens of species of Eucalyptus and Corymbia, mainly causing leaf and shoot blight. Recently, extensive shoot and leaf dieback and stem cankers suspected to be Quambalaria diseases have been found on young Eucalyptus urophylla × E. grandis trees in Guangdong and Hainan Provinces. The occurrence of Quambalaria species and their association with eucalypt hosts within China needs to be investigated for tree diseases management. The isolates from the diseased samples were identified based on their morphological structures and phylogenetic analyses with DNA sequence data for the internal transcribed spacer region and large ribosome subunit RNA of the nuclear rDNA. This work revealed that three species of Quambalaria were present: Quambalaria pitereka from Corymbia citriodora, Q. eucalypti from E. urophylla × E. grandis, both isolated from young eucalypt leaves and shoots in Guangdong Province, and Quambalaria simpsonii, which was isolated from stem cankers of E. urophylla × E. grandis at four different sites across Guangdong and Hainan Provinces. These results confirmed that Quambalaria agents were associated with the diseases occurring on eucalypt hosts in South China. This is the first report of Q. eucalypti in Asia and the first report of Q. simpsonii in China on Eucalyptus trees.