Abstract
Colletotrichum spp. are important pathogens of citrus that cause dieback of branches and postharvest disease. Globally, several species of Colletotrichum have been identified as causing anthracnose of citrus. One hundred and sixty-eight Colletotrichum 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. Colletotrichum australianum sp. nov., C. fructicola, C. gloeosporioides, C. karstii, C. siamense, and C. theobromicola were identified using multi-gene phylogenetic analyses based on seven genomic loci (ITS, gapdh, act, tub2, ApMat, gs, and chs-1) in the gloeosporioides complex and five genomic loci (ITS, tub2, act, chs-1, and his3) in the boninense complex, as well as morphological characters. Several isolates pathogenic to chili (Capsicum annuum), previously identified as C. queenslandicum, formed a clade with the citrus isolates described here as C. australianum sp. nov. The spore shape and culture characteristics of the chili and citrus isolates of C. australianum were similar and differed from those of C. queenslandicum. This is the first report of C. theobromicola isolated from citrus and the first detection of C. karstii and C. siamense associated with citrus anthracnose in Australia.
Highlights
Edible citrus (Citrus spp.) are important fruit crops globally, produced in temperate and tropical climates [1]
A total of 147 Colletotrichum isolates were collected from anthracnose lesions on citrus stems and leaves of trees growing in Victoria and New South Wales and from citrus fruits with anthracnose disease symptoms from supermarkets in Melbourne, Victoria
36 Colletotrichum isolates, 29 were identified to be in the gloeosporioides complex and seven were identified to be in the boninense complex based on analysis of combined intervening 5.8S nrDNA gene (ITS) and tub2 gene sequences
Summary
Edible citrus (Citrus spp.) are important fruit crops globally, produced in temperate and tropical climates [1]. Cumquat (Citrus japonica), grapefruit (Citrus × paradisi), lemon (Citrus limon), lime (Citrus aurantifolia), mandarin (Citrus reticulata), and orange (Citrus × sinensis) are all commercially important citrus species [1,2]. Australia is a major citrus producer with citrus grown in every mainland state [3,4]. In 2019, there was approximately 25,500 ha of citrus production in Australia [5]. Citrus is one of the largest fresh fruit exports from Australia. Australia exported 251,594 tonnes of citrus in 2018, with a total value of $A452.9 million [6]
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