Project description:Colletotrichum caudatum sensu lato is a widespread fungal pathogen of warm-season grasses. The fungus is easily differentiated from other Colletotrichum species through the presence of a unique filiform appendage at the apex of the conidium. Multi-locus phylogenetic analysis of four DNA sequence markers from 21 isolates of C. caudatum s.l. from six grass hosts recovered the morphospecies as a well-supported monophyletic group. Although closely related to other Colletotrichum species pathogenic to warm-season grasses (e.g. C. sublineola, C. falcatum, C. navitas, C. graminicola), the sister taxon placement of C. caudatum remained unclear. Four major subgroups and three monotypic lineages were identified from the C. caudatum s.l. isolates. Despite the presence of localized, taxon-specific incongruence between gene trees and evidence for recombination in the dataset, application of genealogical concordance species recognition criteria diagnosed the four subgroups as phylogenetic species. Traditional morphology-based species concept defines C. caudatum as one species with a broad host range; however, multi-locus phylogenetic analyses refuted this model. Instead, isolates from different hosts were mainly segregated into different lineages. In particular, isolates from the type locale and host (USA, Sorghastrum nutans) collected within a 400 km radius were divided into three distinct species that corresponded with the three sampling sites. These data established that traditional morphological and ecological features are not informative for recognition of taxa within C. caudatum s.l., although there is some evidence that some species may be host specific. To stabilize the application of the name C. caudatum, DNA sequence data from the lectotype was generated, an epitype strain consistent with the type was designated and illustrated, and an emended description of C. caudatum sensu stricto is provided. Colletotrichum alcornii, C. baltimorense, C. somersetense, and C. zoysiae are described as new morphologically cryptic species related to C. caudatum s.s.
Project description:Species from the genus Colletotrichum are the causal agents of anthracnose which contribute to significant losses to the production of commercially grown crops. The genomes of Colletotrichum orbiculare, which infects cucurbits and Nicotiana benthamiana, as well as Colletotrichum gloeosporioides, which infects a wide range of fruits and vegetables, were sequenced. A custom microarray was designed for Colletotrichum orbiculare and used to assess gene expression during infection of Nicotiana benthamiana. Gene expression of Colletotrichum orbiculare growing on its host Nicotiana benthamiana was assessed at 24 hours post inoculation, 3 days post inoculation and 7 days post inoculation. Mycelia growing in vitro and ungerminated conidia were used as controls. Three replicates were performed for each time point.