Salinity tolerance of selected seashore paspalums and bermudagrasses: Root and verdure responses and criteria

Seashore paspalum (Paspalum vaginatum Swartz) is a warm season turfgrass that survives in sand dunes along coastal sites and around brackish ponds or estuaries. The first exposure to salt stress normally occurs in the rhizosphere for persistent turfgrass. Information on diversity in salinity tolerance of seashore paspalums is limited. From Apr. to Oct. 1997, eight seashore paspalum ecotypes (SI 94-1, SI 92, SI 94-2, 'Sea Isle 1', 'Excalibur', 'Sea Isle 2000', 'Salam', 'Adalayd') and four bermudagrass (Cynodon dactylon x C. transvaalensis Butt-Davy) cultivars ('Tifgreen','Tifway','TifSport','TifEagle') were investigated for levels of salinity tolerance based on root and verdure responses in nutrient/sand culture under greenhouse conditions. Different salt levels (1.1 to 41.1 dS(.)m(-1)) were created with sea salt. Measurements were taken for absolute growth at 1.1 (EC(w)0; electrical conductivity of water), 24.8 (EC(w)24), 33.1 (EC(w)32), and 41.1 dS(.)m(-1) (EC(w)40), threshold ECw, and ECw for 25 % growth reduction from EC(w)0 growth (EC(w)25 %). Varying levels of salinity tolerance among the 12 entries were observed based on root, verdure, and total plant yield. Ranges of root characteristics were inherent growth (EC(w)0) = 0.20 to 0.61 g dry weight (DW); growth at EC(w)24 = 0.11 to 0.47 g; growth at EC(w)32 = 0.13 to 0.50 g; growth at EC(w)40 = 0.13 to 0.50 g; threshold ECw = 3.1 to 9.9 dS(.)m(-1); and EC(w)25 % = 23 to 39 dS(.)m(-1). For verdure, ranges were inherent growth at EC(w)0 = 0.40 to 1.07 g DW; growth at EC(w)40 = 0.31 to 0.84 g; and ratio of yields at EC(w)40 to EC(w)0 = 0.54 to 1.03. Ranges for total growth were inherent growth at EC(w)0 = 0.72 to 2.66 g DW; growth at EC(w)24 = 0.55 to 2.23 g; growth at EC(w)32 = 0.54 to 2.08 g; growth at EC(w)40 = 0.52 to 1.66 g; threshold ECw = 2.3 to 12.8 dS(.)m(-1); and EC(w)25 % = 16 to 38 dS(.)m(-1). Significant salinity tolerance differences existed among seashore paspalums and bermudagrasses as demonstrated by root, verdure, and total growth measurements. When grasses were ranked across all criteria exhibiting a significant F test based on root, verdure, and total growth, the most tolerant ecotypes were SI 94-1 and SI 92. Salinity tolerance of bermudagrass cultivars was relatively lower than SI 94-1 and SI 92. For assessing salinity tolerance, minimum evaluation criteria must include absolute growth at EC(w)0 and EC(w)40 dS(.)m(-1) for halophytes, but using all significant parameters of root and total yield is recommended for comprehensive evaluation.