Salinity Tolerance of Seashore Paspalum Ecotypes: Shoot Growth Responses and Criteria

Evaluation of turfgrass salt tolerance is a basic strategy for selecting grasses that can be grown in areas with salt-affected water or soils. Our objectives were to determine the relative salinity tolerances of 32 grasses and to evaluate potential shoot-based criteria for assessing salinity tolerance. Shoot growth responses to salinity of 28 seashore paspalums ( Paspalum vaginatum Swartz) and four bermudagrass [ Cynodon dactylon (L.) × C. transvalensis Burtt-Davy] cultivars were investigated under solution/sand culture in a greenhouse. Turfgrasses were grown in a sea-salt amended nutrient solution. Salinity ranges were 1.1 to 41.1 dS·m -1 based on electrical conductivity of the solution (EC w ). Selection criteria to assess salt tolerance were absolute growth at 1.1 (EC w 0), 24.8 (EC w 24), 33.1 (EC w 32), and 41.1 dS·m -1 (EC w 40); threshold EC w ; EC w for 25% and 50% growth reduction based on EC w 0 growth; and leaf firing (LF) at EC w 0 and EC w 40 (LF0 and LF40, respectively). Significant variations among 32 entries were observed for all shoot responses except threshold EC w . Ranges of values for shoot parameters were: inherent growth at EC w 0 = 0.10 to 0.98 g dry weight (10-fold difference); growth at 24.8 dS·m -1 = 0.11 to 0.64 g; growth at 33.1 dS·m -1 = 0.09 to 0.54 g; growth at 41.4 dS·m -1 = 0.06 to 0.35 g; threshold EC W = 3.9 to 12.3 dS·m -1 ; EC w 25 % = 14 to 38 dS·m -1 ; EC w 50% = 22 to 43 dS·m -1 ; and LF40 = 7% to 41%. Results in this study indicated substantial genetic-based variation in salt tolerance within seashore paspalums. When evaluation of salt tolerance based on shoot responses is attempted at wide salinity levels up to 40 dS·m -1 , all seven criteria exhibiting a significant F test can be used. Five entries (SI 92, SI 93-1, SI 91, SI 93-2, SI 89) were ranked in the top statistical grouping for all seven-growth parameters, followed by SI 90 ranked in six out of seven, and three paspalums (SI 94-1, `Sea Isle 1', and `Taliaferro') were ranked in five out of seven categories.