Colletotrichum - current status and future directions

Abstract

A review is provided of the current state of understanding of Colletotrichum systematics, focusing on species-level data and the major clades. The taxonomic placement of the genus is discussed, and the evolution of our approach to species concepts and anamorph-teleomorph relationships is described. The application of multilocus technologies to phylogenetic analysis of Colletotrichum is reviewed, and selection of potential genes/loci for barcoding purposes is discussed. Host specificity and its relation to speciation and taxonomy is briefly addressed. A short review is presented of the current status of classification of the species clusters that are currently without comprehensive multilocus analyses, emphasising the orbiculare and destructivum aggregates. The future for Colletotrichum biology will be reliant on consensus classification and robust identification 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.

Keywords: Colletotrichum; Glomerella; anamorph-teleomorph linkages; barcoding; database; host specialisation; phylogeny; species concepts; systematics.

Fig. 1A–L.

(see page 182). Disease symptoms caused by Colletotrichum species. The causal organisms have in most cases been identified to species complex level only. A. Anthracnose on strawberry fruit caused by C. nymphaeae (acutatum clade). B. Leaf spot of Brachyglottis repanda caused by C. beeveri (boninense clade). C. Anthracnose symptoms on leaves of Tecomanthe speciosa caused by C. boninense agg. D. Anthracnose of onion bulb caused by C. circinans (dematium clade). E. Anthracnose of banana caused by C. musae (gloeosporioides clade). F. Coffee berry disease caused by C. kahawae subsp. kahawae (gloeosporioides clade). G. Leaf anthracnose of yam caused by C. gloeosporioides agg. H. Anthracnose of aubergine (eggplant) fruit caused by C. gloeosporioides agg. I. Blossom blight of mango caused by an undetermined Colletotrichum sp. J. Anthracnose of mango caused by C. gloeosporioides agg. K. Leaf blight of maize caused by C. graminicola (graminicola clade). L. Anthracnose of bean pod caused by C. lindemuthianum (orbiculare agg.). A, © Ulrike Damm/CBS. B, C, D, H © Landcare Research, New Zealand. E, F, K © Jim Waller/CABI. G © Paul Cannon/CABI. I, J © Barbara Ritchie/CABI. L © Lu Guo-zhong, Dalian, China.

Fig. 2.

Phylogenetic tree derived from a Bayesian analysis of an alignment of ITS (599 bp) sequences, run for 1×10⁷ generations with a GTR+I+Γ model of DNA evolution. Species names are followed by culture number, and status of the culture, where HT = ex-holotype, ET = epitype, NT = ex-neotype, IT = ex-isotype, AUT = authentic culture. Sequences from a number of non-validated cultures have been included in order to represent clades that have not yet been subject to revision based on multilocus data. These are indicated by the symbol §^*.

Fig. 3.

Phylogenetic tree derived from a Bayesian analysis of a partitioned, concatenated alignment of CHS-1 (251 bp), ACT (305 bp), TUB2 (545 bp) and ITS (599 bp) sequences, run for 1×10⁷ generations with a GTR+I+Γ model of DNA evolution for each partition. The major clades recognised in this paper are indicated. Other details as per Fig. 2.

Fig. 4

. Maximum likelihood phylogeny based on an ITS alignment of GenBank accessions of the C. lindemuthianum, C. orbiculare, C. trifolii and C. destructivum species complexes (alignment with ClustalX, 1000 bootstrap replicates, PhyML package).