Species of Mycosphaerellaceae and Teratosphaeriaceae represent over 40% of the fungi identified on eucalypt leaves worldwide. These include some important pathogens that mainly cause leaf blight and spot, and result in increasingly negative impacts on global commercial eucalypt industries. Eucalyptus plantations are commonly cultivated in southern China for solid wood and pulp products. However, the species diversity and geographic distribution of Mycosphaerellaceae and Teratosphaeriaceae, associated with diseased plantation Eucalyptus leaves in China, have not been clarified. In this study, we conducted the first systematic surveys and sample collections of Mycosphaerellaceae- and Teratosphaeriaceae-like fungi from diseased plantation Eucalyptus leaves in southern China. In total, 558 isolates were obtained from 59 sampled sites in five provinces. One isolate was isolated from each tree. According to the disease symptoms, conidia morphological characteristics, and DNA sequence comparisons of ITS, tef1 and tub2 gene regions. The 558 isolates were identified as Teratosphaeria epicoccoides (312 isolates; 55.9%) and T. destructans (246 isolates, 44.1%). Both species were widely distributed in the sampled regions in southern China. The genotypes of T. epicoccoides and T. destructans were determined based on ITS, tef1, and tub2 sequences. The results showed that multiple genotypes of each species of T. epicoccoides and T. destructans exist in China. Additionally, isolates with multiple genotypes were obtained in all five sampled provinces. These results suggest that both T. epicoccoides and T. destructans are not clonal. This study proved that both T. epicoccoides and T. destructans are dominant species and widely distributed on diseased Eucalyptus leaves in southern China. The wide geographic distribution and potential high genetic diversity pose challenges for the disease management of Teratosphaeria leaf blight and leaf spot in China.
Keywords: Teratosphaeria leaf blight; Teratosphaeria leaf spot; forest disease; genetic diversity; leaf pathogen; phylogeny.