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Qi Zhang, Jack Fry, Channa Rajashekar, Dale Bremer and Milton Engelke

Cell membranes play an integral role in freezing tolerance. The objectives of this study were to quantify polar lipids in cold-tolerant ‘Meyer’ zoysiagrass (Zoysia japonica) and cold-sensitive ‘Cavalier’ zoysiagrass (Zoysia matrella) and to evaluate their potential role in freezing tolerance. Grasses were acclimated outside and sampled once monthly between October and January to determine freezing tolerance and lipid composition in rhizomes. Lowest LT50s (temperature resulting in 50% survival) were observed in November for ‘Cavalier’ (−8.5 and −9.6 °C in 2005 and 2006, respectively) and December for ‘Meyer’ (−16.2 and −15.4 °C in 2005 and 2006, respectively). The most abundant lipids in zoysiagrass rhizomes were monogalactosyl diacylglycerol, digalactosyl diacylglycerol, phosphatidylcholine, phosphatidylethanolamine, and phosphatidic acid, which comprised 90% of the polar lipids. Differences in lipid contents and double bond indices (DBI) were detected between ‘Meyer’ and ‘Cavalier’ during cold acclimation, but there were no consistent relationships between lipid classes or DBI and freezing tolerance in zoysiagrass.

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

Zoysiagrass (Zoysia spp.) is recognized for its low requirements for pesticide and fertilizer input, but Meyer (Z. japonica Steud.), the cultivar commonly used in the transition zone of the United States, is slow to establish. We evaluated new zoysiagrass progeny for stolon growth characteristics and rate of establishment and determined the relationship between stolon growth characteristics and coverage. ‘Meyer’, DALZ 0102 (a Z. japonica), and 18 progeny from crosses of ‘Emerald’ (Z. japonica × Z. tenuifolia Willd. ex Thiele) or a Z. matrella (L.) Merr. × Z. japonica were planted as 6-cm diameter plugs on 30.5 × 30.5-cm centers in 1.5 × 1.5-m plots in 2007 and as single 10-cm diameter plugs in 1.2 × 1.2-m plots in 2008 in Manhattan, KS. Data were collected weekly on number of stolons initiated per plug, stolon elongation, and number of stolon branches. Two researchers rated coverage visually near the end of each growing season. Rate of stolon initiation ranged from 2.2/week to 8.6/week. Elongation rate ranged from 18.8 to 65.1 mm/week. At 11 weeks after planting in 2007, four of 18 progeny had superior coverage to ‘Meyer’; at 11 weeks after planting in 2008, 13 of 18 progeny had superior coverage to ‘Meyer’. Rate of stolon initiation was positively correlated (P < 0.01) with zoysiagrass coverage (r = 0.66, in 2007; r = 0.94 in 2008); likewise, stolon elongation was positively correlated with coverage in 2007 (r = 0.52, P < 0.01) and 2008 (r = 0.53, P < 0.05). Stolon initiation or elongation could be used in short-term evaluations to predict rate of zoysiagrass coverage from plugs. Greater stolon initiation or elongation of experimental some zoysiagrass progeny makes them promising for alternatives to ‘Meyer’ for overcoming slow establishment rates.

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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.