A happy accident: a novel turfgrass reference genome

Authors: PHILLIPS, ALYSSA - University Of California, Davis; SEETHARAM, ARUN - Iowa State University; ALBERT, PATRICE - University Of Missouri; AUBUCHON-ELDER, TAYLOR - Donald Danforth Plant Science Center; BIRCHLER, JAMES - University Of Missouri; Buckler, Edward - Ed; GILLESPIE, LYNN - Canadian Museum Of Nature; HUFFORD, MATTHEW - Iowa State University; ROMAY, MARIA CINTA - Cornell University; SORENG, ROBERT - Smithsonian Institute; KELLOGG, ELIZABETH - Donald Danforth Plant Science Center; ROSS-IBARRA, JEFFREY - University Of California, Davis

Submitted to: Genes, Genomes, Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2023
Publication Date: 4/1/2023
Citation: Phillips, A.R., Seetharam, A.S., Albert, P.S., Aubuchon-Elder, T., Birchler, J.A., Buckler IV, E.S., Gillespie, L.J., Hufford, M.B., Romay, M., Soreng, R.J., Kellogg, E.A., Ross-Ibarra, J. 2023. A happy accident: a novel turfgrass reference genome. Genes, Genomes, Genetics. 13(6). Article jkad073. https://doi.org/10.1093/g3journal/jkad073.
DOI: https://doi.org/10.1093/g3journal/jkad073

Interpretive Summary: Kentucky bluegrass, also known as Poa pratensis, is a widely used type of grass for lawns and recreational areas worldwide. Despite its economic importance, researchers had not assembled a reference genome due to its large and complex genetic makeup, which involves characteristics like apomixis, polyploidy, and interspecific hybridization. However, here, we accidentally managed to create a draft assembly of the genome by sampling tissue from a weedy Kentucky bluegrass that was intertwined with another type of grass. The assembled genome consists of 6.09 Gbp with specific characteristics. This study identified a significant number of gene models and found that a substantial portion of the genome is made up of transposable elements. This reference genome was used to study the genetic diversity and population structure of Kentucky bluegrass samples collected from three different North American prairies. The results supported previous findings of high genetic diversity and distinct populations within the species. This reference genome will be a valuable resource for breeding and studying bluegrass varieties used in turfgrass management.

Technical Abstract: Poa pratensis, commonly known as Kentucky bluegrass, is a popular cool-season grass species used as turf in lawns and recreation areas globally. Despite its substantial economic value, a reference genome had not previously been assembled due to the genome’s relatively large size and biological complexity that includes apomixis, polyploidy, and interspecific hybridization. We report here a fortuitous de novo assembly and annotation of a P. pratensis genome. Instead of sequencing the genome of a C4 grass, we accidentally sampled and sequenced tissue from a weedy P. pratensis whose stolon was intertwined with that of the C4 grass. The draft assembly consists of 6.09 Gbp with an N50 scaffold length of 65.1 Mbp, and a total of 118 scaffolds, generated using PacBio long reads and Bionano optical map technology. We annotated 256K gene models and found 58% of the genome to be composed of transposable elements. To demonstrate the applicability of the reference genome, we evaluated population structure and estimated genetic diversity in P. pratensis collected from three North American prairies, two in Manitoba, Canada and one in Colorado, USA. Our results support previous studies that found high genetic diversity and population structure within the species. The reference genome and annotation will be an important resource for turfgrass breeding and study of bluegrasses.