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Ross C. Braun, Jack D. Fry, Megan M. Kennelly, Dale J. Bremer, and Jason J. Griffin

In the transitional climates, warm-season turfgrasses are more heat and drought resistant and require fewer pesticide and fertilizer inputs than cool-season turfgrasses, but an extended winter dormancy period in warm-season turfgrasses makes them less attractive. Our objective was to evaluate color intensity and persistence of colorants applied at two volumes, once or sequentially, on buffalograss (Buchloe dactyloides) maintained at 2.5 inches and zoysiagrass (Zoysia japonica) maintained at 0.5 inch. Field studies were conducted in Manhattan, KS, and Haysville, KS, from Oct. 2013 to May 2014 on dormant ‘Sharpshooter’ and ‘Cody’ buffalograss and ‘Meyer’ zoysiagrass. The colorants Green Lawnger, Endurant, and Wintergreen Plus were applied at 100 or 160 gal/acre in autumn (single application) or autumn plus midwinter (sequential application). Every 2 weeks, visual turf color was rated on a 1 to 9 scale (9 = best) with ratings based on the intensity of the color, not the color (hue) of green. Few differences in color persistence occurred among colorants, but color persisted longer at the higher spray volume. In general, buffalograss receiving a single autumn colorant application had acceptable color (i.e., a visual rating ≥6) for 55–70 days at 100 gal/acre or 55–88 days at 160 gal/acre. Zoysiagrass receiving a single autumn colorant application had acceptable color for 56–97 days at 100 gal/acre or 97–101 days at 160 gal/acre. Across all sites, a sequential midwinter application applied at 160 gal/acre on buffalograss and both application volumes on zoysiagrass provided acceptable green turf color from that point until spring green-up. Most buffalograss plots receiving the sequential midwinter application at 100 gal/acre had acceptable color from that point until spring green-up. Winter color of buffalograss and zoysiagrass can be enhanced by colorant application, and a longer period of acceptable color can be achieved by applying at a higher volume or by including a sequential midwinter treatment.

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Kemin Su, Dale J. Bremer, Richard Jeannotte, Ruth Welti, and Celeste Yang

Cool-season turfgrasses may experience heat stress during summer. Hybrid bluegrasses (HBGs), crosses between kentucky bluegrass [KBG (Poa pratensis L.)] and native texas bluegrass (Poa arachnifera Torr.), have improved heat tolerance but the mechanisms of heat tolerance are poorly understood. Our objectives were to quantitatively profile membrane lipid molecular species in three cool-season turfgrasses exposed to optimal (22/15 °C, 14/10 h light/dark) and supra-optimal temperatures (35/25 °C and 40/30 °C, 14/10 h light/dark). Grasses included a low heat-tolerant tall fescue [TF (Festuca arundinacea Schreb. ‘Dynasty’)], a mid-heat–tolerant KBG (‘Apollo’), and a heat-tolerant HBG (‘Thermal Blue’). At high temperature, glycolipid digalactosyldiacylglycerol (DGDG) in HBG was 12% and 16% greater than in KBG and TF, respectively, and the ratio DGDG to monogalactosyldiacylglycerol was 19% and 44% greater in HBG than in KBG and TF, respectively. Greater heat tolerance in HBG and KBG was associated with higher contents of phosphatidylethanolamine and phosphatidylglycerol, and with reduced overall unsaturation compared with TF. Overall, 20 lipid molecular species were present in greater amounts and another 20 species in lesser amounts in HBG and KBG than in TF. Results suggest 40 membrane lipid molecules are potential biomarkers for heat tolerance and that compositional changes in membrane lipids in response to heat contribute to differences in heat tolerance among cool-season grasses.

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David O. Okeyo, Jack D. Fry, Dale J. Bremer, Ambika Chandra, A. Dennis Genovesi, and Milton C. Engelke

Zoysiagrass (Zoysia spp.) grown under shade on golf courses and in home lawns is slow to recover from damage and declines in quality over time. We evaluated stolon growth and tillering of ‘Meyer’ and Chinese Common (both Z. japonica Steud.); ‘Zorro’, ‘Diamond’, and ‘Cavalier’ [all Z. matrella L. (Merr.)]; ‘Emerald’ (Z. matrella × Z. pacifica Goudsw.); and six experimental progeny from ‘Emerald’ × Z. japonica and reciprocal crosses of Z. japonica × Z. matrella under silver maple (Acer saccharinum L.) shade and in full sun in 2008 and 2009 in Manhattan, KS. A single 6-cm diameter plug was planted in the center of 1.2 m × 1.2-m plots, and data were collected weekly on the number of stolons, stolon elongation, and number of stolon branches. Tiller number was collected at the start and end of each study period, and biomass (excluding roots) was determined at the end of each season. Zoysiagrasses under an average of 76% tree shade exhibited reductions of 38% to 95% in stolon number; 9% to 70% in stolon length; 10% to 93% in stolon branching; and 56% to 98% in biomass. Seven of the 10 grasses exhibited a decline in tiller number in each experiment; none of the grasses differed from ‘Meyer’ in percentage change in tiller number under shade. ‘Emerald’, ‘Cavalier’, ‘Zorro’, and several progeny from crosses between ‘Emerald’ × Z. japonica or reciprocal crosses of Z. matrella × Z. japonica produced more, longer, or more highly branched stolons than ‘Meyer’, suggesting they may have improved recovery potential in shade.