Colletotrichum Species Causing Anthracnose of Citrus in Australia

Abstract

<i>Colletotrichum</i> spp. are important pathogens of citrus that cause dieback of branches and postharvest disease. Globally, several species of <i>Colletotrichum</i> have been identified as causing anthracnose of citrus. One hundred and sixty-eight <i>Colletotrichum</i> isolates were collected from anthracnose symptoms on citrus stems, leaves, and fruit from Victoria, New South Wales, and Queensland, and from State herbaria in Australia. <i>Colletotrichum australianum</i> sp. nov., <i>C. fructicola</i>, <i>C. gloeosporioides</i>, <i>C. karstii, C. siamense</i>, and <i>C. theobromicola</i> were identified using multi-gene phylogenetic analyses based on seven genomic loci (ITS, <i>gapdh</i>, <i>act</i>, <i>tub2</i>, <i>ApMat</i>, <i>gs</i>, and <i>chs-1</i>) in the gloeosporioides complex and five genomic loci (ITS, <i>tub2</i>, <i>act</i>, <i>chs-1</i>, and <i>his3</i>) in the boninense complex, as well as morphological characters. Several isolates pathogenic to chili (<i>Capsicum annuum</i>), previously identified as <i>C. queenslandicum</i>, formed a clade with the citrus isolates described here as <i>C. australianum</i> sp. nov. The spore shape and culture characteristics of the chili and citrus isolates of <i>C. australianum</i> were similar and differed from those of <i>C. queenslandicum</i>. This is the first report of <i>C. theobromicola</i> isolated from citrus and the first detection of <i>C. karstii</i> and <i>C. siamense</i> associated with citrus anthracnose in Australia.