Genome-based reclassification of Actinopolyspora righensis Meklat et al. 2013 as a later heterotypic synonym of Actinopolyspora lacussalsi Guan et al. 2013 and description of Actinopolyspora lacussalsi subsp. lacussalsi subsp. nov. and Actinopolyspora lacussalsi subsp. righensis subsp. nov.

A genome led phylophasic study was designed to determine the taxonomic status of a strain, DSM 45956, recovered from a Saharan desert soil. A wealth of taxonomic data, including average nucleotide identity and DNA:DNA hybridization (DDH) values, showed that the isolate and the type strains of Actinopolyspora lacussalsi and Actinopolyspora righensis belong to the same species. Consequently, it is proposed that A. righensis is a heterotypic synonym of A. lacussalsi. Similarly, DDH values and associated phenotypic data show that A. lacussalsi contains two subspecies, A. lacussalsi subsp. lacussalsi and A. lacussalsi subsp. righensis which includes isolate DSM 45956.

Genotyping of Plasmodiophora brassicae reveals the presence of distinct populations.

BACKGROUND: Plasmodiophora brassicae is a soilborne pathogen of the family Brassicaceae and the causal agent of clubroot disease. In Canada, P. brassicae is now one of the most important constraints to canola (Brassica napus) production, and is managed mainly by the deployment of resistant cultivars. In recent years, however, new strains of the pathogen have emerged that are capable of overcoming host resistance, posing new challenges for disease management. Despite its economic significance, molecular studies of P. brassicae are rare, mainly because this microorganism cannot be cultured outside of its host. RESULTS: Restriction site-associated DNA sequencing (RADseq) was used to examine the genetic diversity within P. brassicae single-spore and field isolates collected from across Canada. The isolates included individuals that were either capable or incapable of causing disease on clubroot resistant canola cultivars. Over 8750 variants were identified through RADseq. Population analysis indicated that most isolates belonged to one of two distinct populations, corresponding with the ability of isolates to cause disease on resistant cultivars. Within each population, there were low levels of genetic diversity. One thousand and fifty of the genetic variants that distinguished the two populations were nonsynonymous, altering the coding sequences of genes. CONCLUSION: The application of RADseq revealed two distinct populations of P. brassicae in Canada, suggesting multiple introductions of the pathogen into the country. The genetic variation found here will be important for future research and monitoring of the pathogen.