Off-Type Grasses of Ultradwarf Bermudagrass Putting Greens: A New Weed Management Issue?.

Ultradwarf bermudagrass putting green use is rapidly increasing in the southeastern United States.  Many golf course superintendents managing these surfaces have noticed off-type grasses in their ultradwarf bermudagrass greens. Anecdotal observations suggest that these off-types vary in texture, color, growth rate, and susceptibility to plant growth regulators compared to commercial ultradwarf cultivars such as TifEagle, MiniVerde, and Champion.  Research was initiated in 2013 with an objective of morphologically and cytogenetically characterizing off-type grasses of ultradwarf putting greens. A total of 52 different bermudagrass samples were selected from golf course putting greens in the southeastern United States in 2013 and cultured from single stolon transplants in a greenhouse environment at the University of Tennessee (Knoxville, TN). Morphology was characterized by measuring internode length, stolon diameter, leaf length, leaf width, leaf length:width ratio, and leaf angle. Considering that internode length was significantly correlated (p < 0.0001) with every morphological parameter except leaf angle (p = 0.0819), grasses were grouped into statistical groupings based on internode length.  Across the 52 selections, internode length ranged from 11 to 56 mm.  The seven grasses in the highest and lowest statistical groups during both experimental runs were selected for further evaluation. Ploidy levels of all 52 samples were determined using flow cytometry.  The majority of the samples were triploid (3n) suggesting that each belonged to the ‘Tifgreen’ family. This response suggests that the off-type grasses collected in this study were not tetraploid (4n) contaminants from collars, fairways, or roughs.  Future research will evaluate how the seven grasses identified in this initial research respond to various management strategies compared to authentic cultivars such as Tifgreen, Tifdwarf, TifEagle, MiniVerde, and Champion.