High soil salinity is one of the major limitations to plant growth in the northern Great Plains. A survey showed that high levels of soil sodium and salinity were detected in 1,900,000 and 700,000 acres of land in North Dakota, respectively (Seelig, 2000). Soil salinity negatively influences plant growth and development, especially during seed germination and early seedling growth because seeds are more likely to be exposed to saline conditions as a result of evaporation and capillary rise of water near the soil surface (Almansouri et al., 2001). Management practices such as implementation of soil amendment, deep plowing, and leaching and drainage have been used to reduce saline problems. However, the most economically effective method is use of salinity-tolerant plants.
Creeping bentgrass (Agrostis stolonifera), fescues (Festuca spp.), and kentucky bluegrass (Poa pratensis) are the most widely used cool-season turfgrasses in the northern Great Plains as a result of good freezing tolerance. However, their relative salt tolerance is ranked moderate [soil electrical conductivity (EC) = 6 to 10 dS·m−1] to sensitive (soil EC less than 3 dS·m−1) (Harivandi et al., 1992). As the salinity problem becomes more and more pronounced, alkaligrass (Puccinellia spp.), a native of the prairies in the western United States and Canada, is highly recommended for home lawns under high saline stress. Harivandi et al. (1982) reported that 48% of Puccinellia spp. seeds germinated after a 15-d exposure to 28.5 dS·m−1 followed by creeping red fescue [F. rubra trichophylla (L.) Gaud.] (24%), perennial ryegrass (Lolium perenne L.) (14%), and creeping bentgrass (1%) but no kentucky bluegrass seed germination was observed. New cultivars are continuously being released in the aforementioned turfgrass species with improved quality such as ‘T-1’ and ‘Alpha’ creeping bentgrass with high competitiveness over annual bluegrass (P. annua L.) (Brede, 2007), ‘Falcon II’ and ‘Houndog V’ tall fescue (F. arundinacea Schreb.) with high drought tolerance (Huang, 2001), ‘Diva’ kentucky bluegrass with high snow molds [Typhula spp. and Macrodochrum nivale (Fr.) Samuels and I.C. Hallett] tolerance (NTEP, 2006), and ‘Fults’ and ‘Salty’ alkaligrass (P. distans) with rapid blight (Labyrinthula spp.) tolerance (Peterson et al., 2005). Salinity tolerance of these new cultivars needs to be evaluated.
Various germination media have been used to evaluate relative salinity tolerance in turfgrasses during seed germination. McCarty and Dudeck (1993) and Wang and Zhang (2010) germinated bentgrass (Agrostis spp.) seeds on agar medium with different salinity levels. Dai et al. (2009) also compared salinity tolerance of greens-type P. annua seeds on agar medium. Germination rate and seedling growth (blade length and tissue weight) of perennial ryegrass, kentucky bluegrass, and tall fescue cultivars under saline conditions were evaluated in hydroponic systems (Horst and Beadle, 1984; Horst and Dunning, 1989; Horst and Taylor, 1983). Camberato and Martin (2004) compared rough bluegrass (P. trivialis L.) germination rate on germination paper moistened with salt solutions. Similar trends were observed that seed germination and seedling growth are reduced as saline stress severity increases regardless of germination media. However, most experiments were conducted to evaluate salt sensitivity in one species. When comparing relative salinity tolerance among different species or additional cultivars, data were often adopted from other studies, in which different germination media might be used. Very limited information is available on the potential influence of seed germination media on salinity tolerance. Horst and Dunning (1989) compared germination and seedling growth of 48 perennial ryegrass cultivars in salt solutions, in which ‘Pennant’, ‘Palmer’, and ‘Fiesta’ had higher salt tolerance than ‘Derby’. In contrast, Dudeck and Peacock (1985) reported that total germination of perennial ryegrass cultivars decreased in the following order: ‘Citation II’ ≥ ‘Pennant’ ≥ ‘Palmer’ > ‘Horizon’ = ‘Derby’ > ‘Fiesta’ when evaluated on agar medium salinized with sea salt mixture. Such different results might be the result of different seed lots (Camberato and Martin, 2004; McCarty and Dudeck, 1993) or possibly the germination media. The research objectives were to evaluate the salinity tolerance of creeping bentgrass, fescues, kentucky bluegrass, and alkaligrass during seed germination on agar medium, on germination paper, or in a hydroponic system and identify potential differences among the three methods. This research will provide the turf industry useful information for selecting appropriate procedures to compare salinity tolerance in turfgrass species or cultivars at germination and seedling stages.
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