Golf Course Management

OCT 2014

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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94 GOLF COURSE MANAGEMENT 10.14 CUTTING EDGE Teresa Carson Off-type grasses of ultradwarf greens Many superintendents 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 regu - lators compared to commercial ultradwarf cultivars such as TifEagle, MiniVerde and Champion. In 2013 we began research to morphologically and cytogenetically char - acterize off-type grasses of ultradwarf put- ting greens. Fifty-two different bermudagrass samples were selected from putting greens in the southeastern U.S. and cultured from single-stolon transplants in a greenhouse en - vironment at the University of Tennessee– Knoxville. Morphology was characterized by measuring internode length, stolon diameter, leaf length, leaf width, leaf length:width ratio, and leaf angle. Because internode length was signifcantly correlated with every morpho - logical parameter except leaf angle, grasses were placed in statistical groupings based on internode length. Across the 52 selections, internode length ranged from 11 to 56 mil - limeters. The seven grasses in the highest and lowest statistical groups during both experi - mental runs were selected for further evalua- tion. Ploidy levels of all 52 samples were deter- mined using fow cytometry. The majority of the samples were triploid (3x), suggesting that each belonged to the Tifgreen family. This response suggests that the off-type grasses collected in this study were not tetraploid (4x) contaminants from collars, fairways or roughs. Future research will evaluate how the seven grasses identifed in this initial re - search respond to various management strate- gies compared to authentic cultivars such as Tifgreen, Tifdwarf, TifEagle, MiniVerde and Champion. — Eric Reasor, James T. Brosnan, Ph.D. (jbrosnan@utk.edu), Robert Trigiano, and John C. Sorochan, Ph.D., University of Tennessee – Knoxville; Brian M. Schwartz, Ph.D., University of Georgia–Tifton; Gerald M. Henry, Ph.D., University of Georgia–Athens. Creeping bentgrass responses to a byproduct containing tryptophan Tryptophan, an essential amino acid that acts as a building block in protein synthesis, is a biochemical precursor for serotonin, nia- cin and auxin in most organisms. When soil moisture is limited, applying biosolids boosted with auxin from tryptophan may increase root production and endogenous hormone levels that can result in plant growth regulation. A byproduct of industrial tryptophan produc - tion, TRP-B, is considered a waste product, but its amino acid and nutrient content make it a possible growth promoter for turfgrasses. The objective of this research was to determine whether applications of TRP-B improve Penn A-4 creeping bentgrass performance more than applications of pure tryptophan and/or urea. Creeping bentgrass plugs taken from sand-based greens at both Virginia Tech and Iowa State were transplanted into pots and al - lowed to re-establish in growth chambers be- fore being treated. Treatments included TRP- B, urea and pure tryptophan + urea applied every 14 days at three different rates. Appli - cation rates were based on the amount of ni- trogen applied (2.18, 10.89 and 21.78 pounds nitrogen/acre). At trial's end (42 days), plant parts were harvested and used for analysis. At 21.78 pounds nitrogen/acre, TRP-B increased root mass by 18.2% and pure tryptophan + urea produced a 16.3% increase compared to urea only. Creeping bentgrass treated with TRP-B can result in increased root produc - tion, but the response is rate-dependent. — Isaac Mertz and Nick E. Christians, Ph.D. (nchris@ iastate.edu), Iowa State University, Ames, Iowa; Erik Ervin, Ph.D., and Xunzhong Zhang, Ph.D., Vir - ginia Tech, Blacksburg, Va. Teresa Carson (tcarson@gcsaa.org) is GCM 's science editor. Photo by Rod Lingle, CGCS Photo by Isaac Mertz

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