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

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