Colletotrichum: complex species or species ... - CBS - KNAW

available online at www.studiesinmycology.orgStudies in Mycology 73: 181–213.Colletotrichum – current status and future directionsP.F. Cannon 1* , U. Damm 2 , P.R. Johnston 3 , and B.S. Weir 31CABI Europe-UK, Bakeham Lane, Egham, Surrey TW20 9TY, UK and Royal Botanic Gardens, Kew, Richmond TW9 3AB, UK; 2 CBS-KNAW Fungal Biodiversity Centre,Uppsalalaan 8, 3584 CT Utrecht, The Netherlands; 3 Landcare Research, Private Bag 92170 Auckland, New Zealand*Correspondence: Paul Cannon, p.cannon@cabi.orgAbstract: A review is provided of the current state of understanding of Colletotrichum systematics, focusing on species-level data and the major clades. The taxonomicplacement of the genus is discussed, and the evolution of our approach to species concepts and anamorph-teleomorph relationships is described. The application of multilocustechnologies to phylogenetic analysis of Colletotrichum is reviewed, and selection of potential genes/loci for barcoding purposes is discussed. Host specificity and its relation tospeciation and taxonomy is briefly addressed. A short review is presented of the current status of classification of the species clusters that are currently without comprehensivemultilocus analyses, emphasising the orbiculare and destructivum aggregates. The future for Colletotrichum biology will be reliant on consensus classification and robustidentification tools. In support of these goals, a Subcommission on Colletotrichum has been formed under the auspices of the International Commission on Taxonomy of Fungi,which will administer a carefully curated barcode database for sequence-based identification of species within the BioloMICS web environment.Key words: anamorph-teleomorph linkages, barcoding, Colletotrichum, database, Glomerella, host specialisation, phylogeny, systematics, species concepts.Published online: 15 September 2012; doi:10.3114/sim0014. Hard copy: September 2012.Studies in MycologyINTRODUCTIONThe genus Colletotrichum includes a number of plant pathogensof major importance, causing diseases of a wide variety of woodyand herbaceous plants. It has a primarily tropical and subtropicaldistribution, although there are some high-profile species affectingtemperate crops. Fruit production is especially affected, both highvaluecrops in temperate markets such as strawberry, mango, citrusand avocado, and staple crops such as banana. Colletotrichumspecies cause devastating disease of coffee berries in Africa, andseriously affect cereals including maize, sugar cane and sorghum.The genus was recently voted the eighth most important group ofplant pathogenic fungi in the world, based on perceived scientificand economic importance (Dean et al. 2012).As plant pathogens, Colletotrichum species are primarilydescribed as causing anthracnose diseases, although othermaladies are also reported such as red rot of sugar cane, coffeeberry disease, crown rot of strawberry and banana, and brownblotch of cowpea (Lenné 2002). Anthracnose disease symptomsinclude limited, often sunken necrotic lesions on leaves, stems,flowers and fruit, as well as crown and stem rots, seedling blightetc. (Waller et al. 2002, Agrios 2005). A range of disease symptomsis illustrated in Fig. 1. Many species may be seed-borne and cansurvive well in soil by growing saprobically on dead plant fragments,and may be spread via water-splash dispersal of conidia and airtransmission of ascospores from the sexual morph (Nicholson &Moraes 1980). Infection occurs via an appressorium that developsfrom the germinating spore on the plant surface, followed by turgordrivenpenetration of the cuticle (Deising et al. 2000) and in somecases also of epidermal cells by infective hyphae (Bailey et al.1992). Establishment within plant tissues is aided via productionCopyright CBS-KNAW Fungal Biodiversity Centre, P.O. Box 85167, 3508 AD Utrecht, The Netherlands.by the fungus of host-induced virulence effectors (Kleeman et al.2012, O’Connell et al. 2012). Nascent colonies in most cases thenenter a biotrophic phase with infected tissues remaining externallysymptomless and which may be short (1–3 d; O’Connell et al.2000) or extended and presumably involving dormancy (Prusky& Plumbley 1992). Then, the fungus enters a necrotrophic phasethat results in significant death of plant cells and the emergenceof pathogenic lesions. This delayed onset of disease symptomsmay lead to significant post-harvest losses, with apparently healthycrops degenerating in storage (Prusky & Plumbley 1992). Thebiotrophic life strategies adopted by Colletotrichum species mayalso contribute to their prominence as symptomless endophytesof living plant tissues (Lu et al. 2004, Joshee et al. 2009, Rojas etal. 2010, Yuan et al. 2011). There are no comprehensive modernreviews of the biology, pathology and host/parasite interactionsof Colletotrichum species, but useful information can be found inBailey & Jeger (1992) and Prusky et al. (2000).Colletotrichum species are also extensively studied as modelorganisms for research into genetics. This work has a long history;the first investigation into mating types in Glomerella was publisheda century ago (Edgerton 1912, 1914), and genetic mechanisms inG. cingulata were extensively studied in the 1940’s and 50’s (e.g.Andes 1941, Lucas et al. 1944, Wheeler 1950, 1954, Olive 1951).Research into host/parasite systems has had almost as long ahistory, originating with work on the C. lindemuthianum/Phaseolusvulgaris interaction by Barrus (1918). Mechanisms of infection anddisease development in the same model system were extensivelystudied in the 1980’s (e.g. Bell et al. 1984, O’Connell et al. 1985,1986).Maize anthracnose caused by Colletotrichum graminicola isan economically important disease on a global level, stimulatingYou are free to share - to copy, distribute and transmit the work, under the following conditions:Attribution:You must attribute the work in the manner specified by the author or licensor (but not in any way that suggests that they endorse you or your use of the work).Non-commercial: You may not use this work for commercial purposes.No derivative works: You may not alter, transform, or build upon this work.For any reuse or distribution, you must make clear to others the license terms of this work, which can be found at http://creativecommons.org/licenses/by-nc-nd/3.0/legalcode. Any of the above conditions can be waived if you getpermission from the copyright holder. 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