Origin and evolution of cultivated Agrostis spp.




Amundsen, Keenan

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Creeping bentgrass (Agrostis stolonifera L.) is a highly outcrossing allotetraploid species important to the turfgrass industry because it has unique growth and aesthetic characteristics that make it ideally suited for use in high quality turf stands. There are between 150 and 200 species of Agrostis (bentgrasses) and the relationships between species are not clearly understood. Resolving these relationships is complicated in part because many of the species share similar morphological features and interspecific hybridization is common, making taxonomic classification difficult. Knowledge of the evolution of Agrostis species would provide turfgrass breeders with information on the origins of species and potential sources of novel germplasm. In the present study 305 Agrostis accessions were examined to explore the evolutionary relationships within the Agrostis genus. Flow cytometry experiments were performed on each accession to measure DNA content and make ploidy predictions. MITE display molecular markers were designed and 1,309 were used to assess genetic diversity within a subset of these Agrostis accessions. Fragments of the trnL-trnF and atpI-atpH intergenic spacer regions of the chloroplast genome were also sequenced and used to infer the phylogeny of the chloroplast genome. This data allowed for the prediction of candidate diploid progenitors of cultivated Agrostis species, identification of geographic regions of diverse germplasm, and demonstration of narrowing of the cultivated Agrostis gene pool. The data presented here gives Agrostis breeders valuable information to incorporate novel germplasm in their programs and a direction for recreating the polyploidization events that have led to the cultivated turf-type Agrostis species.



Agrostis, Ploidy, Transposable elements, Diversity analysis, Reticulate phylogeny