Two new species of Cytospora (Diaporthales, Cytosporaceae) causing canker disease of Malus domestica and M. sieversii in Xinjiang, China

Apple tree canker is a serious disease caused by species of <i>Cytospora</i>. Xinjiang Uygur Autonomous Region is one of the most important apple-producing areas in China. However, losses due to apple <i>Cytospora</i> canker have seriously damaged the apple industry and affected the economic development of the apple growers in this region. In this study, we used morphological characteristics combined with multilocus phylogenetic analyses of the ITS, <i>act</i>, <i>rpb2</i>, <i>tef1</i> and <i>tub2</i> loci to identify isolates from apple (<i>Malusdomestica</i>) and wild apple (<i>M.sieversii</i>). As a result, <i>C.hippophaopsis</i> <b>sp. nov.</b> from <i>M.sieversii and C.shawanensis</i> <b>sp. nov.</b> from <i>M.domestica</i> were discovered and proposed herein. Pathogenicity tests were further conducted on 13 varieties of apple and wild apple, which confirmed <i>C.hippophaopsis</i> and <i>C.shawanensis</i> as canker pathogens. Meanwhile, <i>C.hippophaopsis</i> is generally more aggressive than <i>C.shawanensis</i> on the tested varieties of apple and wild apple.