Diversity and Pathogenicity of Six Diaporthe Species from Juglans regia in China

Walnut (Juglans regia L.) is cultivated extensively in China for its substantial economic potential as a woody oil species. However, many diseases caused by Diaporthe greatly affect the health of Juglans regia trees. The present study revealed the presence of Diaporthe species from Juglans regia. A total of six species of Diaporthe were isolated from twigs of Juglans regia in three provinces in China, including two known species (Diaporthe gammata and D. tibetensis) and four novel species (D. chaotianensis, D. olivacea, D. shangluoensis and D. shangrilaensis). Phylogenetic relationships of the new species were determined by multilocus phylogenetic analyses based on partial sequences of the internal transcribed spacer (ITS) region, calmodulin (cal) gene, histone H3 (his3) gene, translation elongation factor 1-α (tef1-α) gene and β-tubulin (tub2) gene. Pathogenicity tests indicated that all Diaporthe species obtained in this study were confirmed as pathogens of Juglans regia. This study deepens the understanding of species associated with several disease symptoms in Juglans regia and provides useful information for effective disease control.