Quambalaria species associated with eucalypt diseases in southern China

Abstract

The genus <i>Quambalaria</i> includes several important pathogens of species of <i>Eucalyptus</i> and <i>Corymbia</i>, mainly causing leaf and shoot blight. Recently, extensive shoot and leaf dieback and stem cankers suspected to be <i>Quambalaria</i> diseases have been found on young <i>Eucalyptus urophylla × E. grandis</i> trees in Guangdong and Hainan Provinces. The occurrence of <i>Quambalaria</i> 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 <i>Quambalaria</i> were present: <i>Quambalaria pitereka</i> from <i>Corymbia citriodora</i>, <i>Q. eucalypti</i> from <i>E. urophylla × E. grandis</i>, both isolated from young eucalypt leaves and shoots in Guangdong Province, and <i>Quambalaria simpsonii</i>, which was isolated from stem cankers of <i>E. urophylla × E. grandis</i> at four different sites across Guangdong and Hainan Provinces. These results confirmed that <i>Quambalaria</i> agents were associated with the diseases occurring on eucalypt hosts in South China. This is the first report of <i>Q. eucalypti</i> in Asia and the first report of <i>Q. simpsonii</i> in China on <i>Eucalyptus</i> trees.