Golf Course Management

FEB 2016

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

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02.16 GOLF COURSE MANAGEMENT 103 areas of the turf stand. Bacterial streaming was present when cut ends of symptomatic plants were observed microscopically at 100×. The suspected causal agent was isolated by cutting leaf tissue into 1-mm to 3-mm seg - ments, which were macerated with a sterile scal- pel. Tenfold serial dilutions up to 1 × 10 −4 were performed in sterile saline solution; 10 µl of each suspension was plated onto nutrient agar and incubated at room temperature (21 C) for seven to 10 days. The most frequently observed colonies were mucoid, convex and yellow-pigmented. Pure cultures of the putative pathogen were obtained by selecting single-bacterial colonies to grow in trypticase soy broth medium for 10 days. These were used to inoculate four replicates of Lolium perenne cultivar CSI plants grown in Sure - mix perlite in 24-ounce (709-ml) foam cups. Healthy perennial ryegrass plants were inocu - lated with 5 ml of a suspension by adding drops of the suspension to blades of sterile scissors that were then used to cut the healthy plants. Inoculations with the predominant bacte - rium obtained from original samples resulted in symptoms of chlorosis and leaf tip dieback after four days, and severe necrosis after seven days. When symptomatic leaves of the inocu - lated plants were cut, heavy bacterial streaming was observed microscopically. Isolation of the bacterium from inoculated perennial ryegrass plants was performed to fulfll Koch's postu - lates. Once isolated, a single bacterial colony was identifed via DNA testing, which indi - cated the causal agent was a member of the Xant omonas genus, with 100% sequence sim - ilarity to X. translucens pv. Graminis (GenBank Accession AY855873.1). The same aerobic, gram-negative bacterium has been consistently isolated from inoculated, symptomatic pe - rennial ryegrass plants thus far. Xant omonas translucens is a known pathogen on other turf - grass species. Multiple fungicide applications are typi - cally made in an effort to control this formerly unidentifed disease, often misdiagnosed as Leptosphaerulina leaf blight. Understanding this as a bacterial and not a fungal disease should result in a considerable cost savings from ineffective fungicide applications as well as a reduction of their environmental impact. To our knowledge, this is the frst report of a bacterial disease affecting a turf-type peren - nial ryegrass species in the United States. Source: Plant Disease, September 2015, 99(9):1270 P.R. Giordano is a turfgrass specialist for Bayer Crop - Science, Guelph, Ontario; Q. Zeng is an assistant agri- cultural scientist II in the Department of Plant Pathology and Ecology, Connecticut Agricultural Experiment Station, New Haven, Conn.; N.M. Dykema is a research assistant III/S, A.R. Detweiler is a retired research assistant III, and J.M. Vargas Jr. is a professor in the Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing. Ergot in perennial ryegrass seed felds in eastern Oregon Jeremiah K. S. Dung, Ph.D.; Stephen Alderman, Ph.D.; Darrin L. Walenta, M.S.; and Philip B. Hamm, Ph.D. Ergot, caused by Claviceps purpurea, is a major disease of perennial ryegrass grass grown for seed in eastern Oregon. The ob - jective of this research was to quantify and describe the spatial patterns of ergot severity in each of three 123.5-acre (50-hectare) com - mercial felds of perennial ryegrass grown for seed in 2012 and 2013. A total of 1,433 and 1,405 quadrats were sampled among the three felds in 2012 and 2013, respectively, and the percentage of quadrats with ergot ranged from 59% to 90%. The mean incidence of infected seed heads in each quadrat ranged between 13% and 29%, while mean severity in each quadrat ranged from 0.2 to 0.5 sclerotia per seed head. Signifcant autocorrelation and clustering were observed in all three felds in both years. The mean number of ergot scle - (report) Healthy perennial ryegrass seeds are pictured to the left of the penny, and ergot sclerotia are on the right. Photo by Jeremiah Dung

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