Cytospora and Diaporthe Species Associated With Hazelnut Canker and Dieback in Beijing, China

Abstract

Hazelnut (<i>Corylus heterophylla</i> Fisch.) is an important nut crop in China but has been declining owing to the destructive effects of fungal branch canker and dieback. The identification and management of these pathogens are difficult because of the lack of attention to branch canker, insufficient understanding of phylogenetic, and overlapping morphological characteristics of the pathogens. In total, 51 strains were isolated from Chinese wild hazelnut in this study, and three species of <i>Cytospora</i> and two of <i>Diaporthe</i> were identified through morphological observation and multi-locus phylogenetic analyses (ITS, <i>act</i>, <i>rpb2</i>, <i>tef1-α</i>, and <i>tub2</i> for <i>Cytospora</i>; ITS, <i>cal</i>, <i>his3</i>, <i>tef1-α</i>, and <i>tub2</i> for <i>Diaporthe</i>). Three new species, <i>Cytospora corylina</i>, <i>C. curvispora</i>, and <i>Diaporthe corylicola</i>, and two known species, <i>Cytospora leucostoma</i> and <i>Diaporthe eres</i>, grew at 5-30°C and a pH of 3.0-11.0, with optimum growth at approximately 25°C and pH 4.0-7.0. Additionally, the effects of six carbon sources on mycelial growth were investigated. This study explored the main pathogenic fungi species of <i>Corylus heterophylla</i>, completed the corresponding database of pathogenic fungi information, and clarified their biological characteristics. Moreover, the results of this study provided a theoretical basis for <i>Corylus heterophylla</i> disease management and prevention in China.