The genetic and phenotypic variability of interspecific hybrid bermudagrasses (Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy) used on golf course putting greens

Abstract

Main conclusionSome interspecific hybrid bermudagrass cultivars used on golf course putting greens are genetically unstable, which has caused phenotypically different off-type grasses to occur in production nurseries and putting surfaces. Management practices to reduce the occurrence of off-type grasses in putting green surfaces and the effect they can have on putting quality and performance need to be researched until genetically stable cultivars are developed.Golf course putting green surfaces in subtropical and tropical climates are typically planted with an interspecific hybrid bermudagrass (Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy), because of the superior putting quality and performance of these cultivars. ‘Tifgreen’ was one of the first interspecific hybrids developed for putting green use in lieu of common bermudagrass. However, off-type grasses began appearing in established Tifgreen stands soon after commercial release. Off-type grasses are those with different morphology and performance when compared to the surrounding, desirable cultivar. Off-types have the potential to decrease surface uniformity, which negatively affects putting surface quality. However, several unique off-types from Tifgreen have been selected as commercial cultivars, the first being ‘Tifdwarf’; then ‘Floradwarf’, ‘MS-Supreme’, ‘Pee Dee-102’, and ‘TL-2’, identified later. The cultivars ‘Champion Dwarf’, ‘P-18’, ‘RJT’, and ‘Emerald Dwarf’ were subsequently selected as off-types in Tifdwarf. The naturally occurring off-types and cultivars that have been identified within the Tifgreen family have widely differing phenotypes; however, they are reported to be genetically similar, supporting the hypothesis that their occurrence is a result of somatic mutations. Genetic instability in currently available commercial cultivars is likely to lead to the continued presence of off-types in production nurseries and putting greens. Additional research is needed to understand the nature of genetic instability in Tifgreen-derived cultivars and how to manage its consequences to develop new cultivars, but also strategies for eradication of off-types in pedigree nursery production and end-site putting greens.

Growing Degree Day Models for Plant Growth Regulator Applications on Ultradwarf Hybrid Bermudagrass Putting Greens

“…U ltradwarf hybrid bermudagrass cultivars [ Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy] are frequently used on golf course putting greens (Reasor et al, 2016). Plant growth regulators (PGRs) are commonly applied to bermudagrass putting greens to reduce vertical shoot growth and maintain consistent playing surfaces (Fagerness et al, 2000; McCullough et al, 2007).…”

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

“…The inability of GBS, as well as other molecular marker techniques, to distinguish off-types from hybrid bermudagrass cultivars used on putting greens could be the result of aneuploidy within the ‘Tifgreen’-cultivar family (B.M. Schwartz, unpublished data, 2016; [ 36 ]). Reasor et al [ 36 ] suggested that aneuploidy could have resulted during the original hybridization of ‘Tifgreen’ or through intense putting green management techniques.…”

“…Schwartz, unpublished data, 2016; [ 36 ]). Reasor et al [ 36 ] suggested that aneuploidy could have resulted during the original hybridization of ‘Tifgreen’ or through intense putting green management techniques. It is expected that some variant locations are not going to be sampled by random chance due to the sparse nature of the GBS analysis.…”

“…Soon after its commercial release, ‘Tifdwarf’ was selected from a somatic mutation in a ‘Tifgreen’ establishment [ 7 , 8 ]. Despite being genetically unstable [ 9 , 10 ], ‘Tifgreen’ and ‘Tifdwarf’ are used on putting surfaces; however, superior mutations have been released as new “ultradwarf” cultivars [ 36 ]. Ultradwarf bermudagrass cultivars are classified due to their more diminutive morphology (i.e., internode length and leaf length and width) compared to ‘Tifdwarf’.…”

“…Additionally, Roche and Loch [ 37 ] stated that morphological characterization could provide useful information to further research for adaptation and management of different hybrid bermudagrasses. Researchers have used morphological characterizations to compare hybrid bermudagrass cultivars within the ‘Tifgreen’ family [ 31 , 37 ]; however, morphological inconsistencies suggest that molecular techniques are also needed to accurately evaluate hybrid bermudagrass diversity [ 36 ].…”