Genotypic and phenotypic evaluation of off-type grasses in hybrid bermudagrass (Cynodon dactylon (L.) Pers. x C. transvaalensis burtt-Davy) putting greens using genotyping-by-sequencing and morphological characterization

Authors: REASOR, ERIC - University Of Tennessee; BROSNAN, JAMES - University Of Tennessee; STATON, MARGARET - University Of Tennessee; LANE, THOMAS - University Of Tennessee; TRIGIANO, ROBERT - University Of Tennessee; Wadl, Phillip; CONNER, JOANN - University Of Georgia; SCHWARTZ, BRIAN - University Of Georgia

Submitted to: Hereditas
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2017
Publication Date: 8/18/2017
Citation: Reasor, E.H., Brosnan, J.T., Staton, M.E., Lane, T., Trigiano, R.T., Wadl, P.A., Conner, J.A., Schwartz, B.M. 2017. Genotypic and phenotypic evaluation of off-type grasses in hybrid bermudagrass [Cynodon dactylon (L.) Pers. x C. transvaalensis burtt-Davy] putting greens using genotyping-by-sequencing and morphological characterization. Hereditas. 155:8. https://doi:10.1186/s41065-017-0043-3.
DOI: https://doi.org/10.1186/s41065-017-0043-3

Interpretive Summary: Hybrid bermudagrass cultivars are widely used grasses on golf courses and in particular for putting greens in the southern U.S. Golf course managers and golfers have the expectation that putting greens are uniform in appearance and quality. However the cultivars used for putting surfaces are thought to be genetically unstable leading to off-types which appear different and can alter the aesthetic and playing quality of putting greens, causing problems for management of golf courses. Researchers at the University of Tennessee and the University of Georgia and a USDA scientist at Charleston investigated genetic variation among off-types and hybrid bermudagrasses used on putting greens. Their objectives were to explore the genetic and the physical appearance among off-type grasses sampled from hybrid bermudagrass putting greens using DNA fingerprinting and morphological characterization. The fingerprinting and characterization of physical appearance determined that most off-type grasses in hybrid bermudagrass putting greens are genetically similar while varying in appearance. Golf course putting greens are intensely managed surfaces subjected to daily mowing, annual aeration and cultivation, as well as treatment with plant growth regulators and silica sand topdressing on a weekly basis. Any of these practices could modify gene expression associated with hybrid bermudagrass physical appearances. Future studies of gene expression changes as a result of these maintenance practices could benefit researchers and industry practitioners to better understand how putting green management could potentially lead to the occurrence of off-type grasses in hybrid bermudagrass putting surfaces.

Technical Abstract: Interspecific hybrid bermudagrass (Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt-Davy) is one of the most widely used grasses on golf courses, with cultivars derived from ‘Tifgreen’ or ‘Tifdwarf’ particularly used for putting greens in the southern agronomic region. Many bermudagrass cultivars established for putting surfaces can be genetically unstable and lead to the occurrence of weedy off-type grasses that vary in phenotype. Beginning in 2013, off-type and desirable hybrid bermudagrass samples were collected from golf course putting greens throughout the southeastern United States and genetically and phenotypically catalogued using genotyping-by-sequencing (GBS) and morphological characterization. GBS determined that 11% of off-type and desirable samples from putting surfaces were genetically divergent from standard cultivars such as Champion, MiniVerde, Tifdwarf, TifEagle, and Tifgreen. In addition, GBS was unable to genetically distinguish all standard cultivars from one another likely due to their genetic origin and clonal propagation practices; however, over 90000 potentially informative nucleotide variants were identified among the triploid hybrid cultivars. GBS was able to differentiate triploid hybrids from diploid (C. transvaalensis) and tetraploid (C. dactylon) progenitor species and separated triploid hybrids of the Tifgreen-cultivar family from those of different lineage (i.e., ‘Tifway’). Although few genetic differences were found in this research, samples harvested from golf course putting greens had variable morphology and clustered into three distinct phenotypic groups. The majority of off-type grasses in hybrid bermudagrass putting greens are genetically similar with variable morphological traits leading to the potential to compromise surface functionality and aesthetics.