Molecular markers delimit cryptic species in Ceratocystis sensu stricto

Ceratocystis sensu stricto is a genus of closely related fungi that are mostly plant pathogens. Morphological variation between species in this genus is limited and species delineation is strongly reliant on phylogenetic inference. Primary support for many of the species is based on the ITS region which, on its own, can be used to delineate all species described in the genus. However, the recent discovery of two ITS types in a single isolate of Ceratocystis questions the use of this marker in taxonomic studies. The aim of this study was to consider the potential use of alternative gene regions to support the species boundaries in this genus. The phylogenetic value of the βT 1 and EF 1-α gene regions, generally used in combination with ITS, were re-evaluated and compared to five single copy protein coding genes (CAL, RPBII, MS204, FG1093 and Mcm7). As an alternative approach, genome-wide single nucleotide polymorphisms (SNPs) were identified and evaluated as diagnostic markers to distinguish between the species. Fifteen species residing in Ceratocystis were used in this study. None of the protein coding genes could be used to distinguish all species but a combination of the βT 1, MS204 and RPBII gene regions resolved 11 of the 15 described species. Unique SNP markers were identified for 13 of the species and these provided significant additional support for most of the established taxon boundaries. Other than ITS, none of the markers tested could distinguish between C. acaciivora and C. manginecans and these species are, therefore, reduced to synonymy with the name C. manginecans being retained. Results of this study also revealed the likely existence of additional species in Ceratocystis.Tree Protection Co-operative Programme (TPCP), the National Research Foundation (NRF) as well as the Genomics Research Institute (GRI) at the University of Pretoria. Also the Thuthuka Foundation (grant no 80670) .http://link.springer.comjournal/11557hb201

Ceratocystis species, including two new taxa, from Eucalyptus trees in South Africa

The ascomycete genus Ceratocystis (Microascales, Ceratocystidaceae) includes important fungal pathogens of trees, including Eucalyptus species. Ceratocystis species and their Thielaviopsis asexual states are typically associated with insects, such as nitidulid beetles, that spread them over long distances. Eucalyptus trees comprise a substantial component of the forestry industry in South Africa, however, limited information is available regarding Ceratocystis species that infect these trees. In this study, Ceratocystis species were collected from wounds on Eucalyptus trees in all the major plantation regions of South Africa, as well as from insects associated with these wounds. Both morphology and multigene DNA sequence analyses, using three nuclear loci, were used to identify the Ceratocystis species. Of the 260 isolates collected, nine Ceratocystis species, of which two were represented only by their Thielaviopsis anamorph states were identified. These species were C. eucalypticola, C. pirilliformis, C. savannae, C. oblonga, C. moniliformis, T. basicola, T. thielavioides and two Ceratocystis species that are described here as C. salinaria sp. nov. and C. decipiens sp. nov. Insects associated with these Ceratocystis species were Brachypeplus depressus (Nitidulidae), Carpophylus bisignatus, C. dimidiatus (Nitidulidae), Xyleborus affinis (Scolytidae), Litargus sp. (Mycetophagidae) and a Staphylinid (Staphylinidae) species.National Research Foundation of South Africa (NRF), the THRIP Initiative of the Department of Trade and Industry (THRIP/DST), members of the Tree Protection Cooperative Programme (TPCP) and the University of Pretoria.http://link.springer.com/journal/13313hb201