Effects of Trinexapac-Ethyl on the Salinity Tolerance of Two Ultradwarf Bermudagrass Cultivars

Studies on bermudagrasses (Cynodon spp.) have demonstrated variability in salinity response among species and cultivars. However, information on ultradwarf bermudagrass cultivars in relative salinity tolerance associated with trinexapac-ethyl (TE) [4-(cyclopropyl-α-hydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid ethyl ester], a cyclohexanedione type II plant growth regulator (PGR), remains unknown. Therefore, two replicated greenhouse studies were conducted to determine the salinity tolerance of two ultradwarf bermudagrass cultivars treated with TE on turfgrass quality (TQ), total root biomass, and root and shoot tissue nutrient concentration. Turfgrasses included `TifEagle' and `Champion' bermudagrass (Cynodondactylon(L.) Pers. × C. transvaalensisBurtt-Davy). Daily sodium chloride (NaCl) exposure was 0, 12.90 (8,000 ppm), 25.80 (16,000 ppm), and 38.71 dS·m–1 (24,000 ppm). Biweekly TE applications (active ingredient 0.02 kg·ha–1) were initiated 2 weeks after salinity exposure. `Champion' was more salt-tolerant than `TifEagle' based on TQ and root mass. At 12.90, 25.80, and 38.71 dS·m–1 of NaCl, nontreated (without TE) `Champion' consistently outperformed nontreated `TifEagle' with greater TQ on most rating dates. At 12.90 dS·m–1, TE treated `Champion' (8.0) had greater TQ than nontreated `TifEagle' (6.1) at week 10. Regardless of TE application, after 2 weeks of applying 25.80 dS·m–1 of NaCl, both cultivars fell below acceptable TQ (–1. In conclusion, the two bermudagrass cultivars responded differently when exposed to moderate levels of NaCl.