Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2011
Publication Date: 5/30/2011
Citation: Harris-Shultz, K.R., Schwartz, B.M., Brady, J.A. 2011. Identification of SSR markers that differentiate bermudagrass cultivars derived from 'Tifgreen'. Journal of the American Society for Horticultural Science. 136(3):211-218. Interpretive Summary: Bermudagrass is the most common turfgrass grown on southeastern golf course greens. The release of bermudagrass cultivar ‘Tifgreen’ in 1956 revolutionized putting green quality as this cultivar could be mowed at 4.7 mm which enhanced ball roll. Thus, golf courses in the southern U.S. rapidly converted their greens to ‘Tifgreen’. A few years later, off-types were discovered on ‘Tifgreen’ putting greens and one was released in 1965 and named ‘Tifdwarf’. Since the 60’s, more off-types have been found in ‘Tifgreen’ or ‘Tifdwarf’ putting greens or production fields, from which many off-types with the most dwarf growth habit have been released as cultivars. For years people have speculated why ‘Tifgreen’ and ‘Tifdwarf’ are mutating and the contamination of monoculture greens with off-types has lead to legal and management problems. Furthermore, identification of ‘Tifgreen’-derived cultivars is very difficult as each is morphologically and genetically very similar. In this study we identified genetic markers to identify three of the most commonly grown ‘Tifgreen’-derived cultivars. We show that different regions of the DNA have changed, as compared to ‘Tifgreen’, in the three cultivars, and that some loci are actively changing in ‘Tifdwarf’. Our study produced the first set of SSR markers to identify ‘Tifgreen’-derived cultivars and gives insight into how, and possibly why, the ‘Tifgreen’ derived cultivars are mutating.
Technical Abstract: The release of the bermudagrass triploid hybrid ‘Tifgreen’ revolutionized southeastern United States golf course greens. Off-types within this cultivar began to be identified soon after the initial plantings, and through the last 50 years many of the best performing off-types have been released as new cultivars. Examination of some of the most popular somatic mutants with a new set of 47 simple sequence repeat (SSR) markers and 23 previously discovered genomic SSR markers, identified five polymorphic fragments (as compared to ‘Tifgreen’) among three cultivars, TifEagle, MiniVerde, and Tifdwarf. Each polymorphism appears to be a slight increase/decrease in microsatellite repeat number and the polymorphic fragments are unique for each cultivar. Two primers amplify fragments that are actively mutating in ‘Tifdwarf’ and more than one polymorphic fragment was identified in ‘MiniVerde’. Thus, the same loci are not mutating in all the ‘Tifgreen’-derived cultivars, some loci are actively mutating in ‘Tifdwarf’, and it is likely that many loci have mutated per cultivar as compared to ‘Tifgreen’. This set of SSR markers are the first to identify repeatable polymorphic fragments among ‘Tifgreen’-derived cultivars and gives insight into the nature of the mutations that exist within ‘Tifgreen’.