Effect of Glycinebetain Seed Priming on Turfgrass Germination Under Drought, Salinity, and Sub-optimal Temperatures

Glycinebetaine (GB) seed priming enhances stress tolerance in various plants during germination and seedling growth stages; however, information on turfgrass is limited. In this study, GB was used to prime turf seeds to determine its efficacy in enhancing tolerance to abiotic stresses. Unprimed and primed (5, 10, and 50 mM solution of GB or distilled water) seeds of perennial ryegrass (Lolium perenne) (PR), tall fescue (Festuca arundinacea) (TF), creeping bentgrass (Agrostis palustris) (CB), Kentucky bluegrass (Poa pratensis) (KB), bermudagrass (Cynodon dactylon) (BER), and zoysiagrass (Zoysia japonica) (ZOY) were germinated under drought (0, -0.4, -0.8, and -1.2 MPa), salinity (0, 5, 10, 15, and 20 dS m^-1), or sub-optimal temperatures [optimal temperature (opt.), opt.±5 ºC, and opt.±10 ºC]. Tolerance to the stresses were determined as relative final germination percentage (FGP) and daily germination rate (DGR), expressed as percentage of germination under stress compared to non-stress in each species. Daily germination rate and FGP decreased with increasing stress level, except under high temperatures (opt.+5 ºC and opt.+10 ºC), with higher reduction in DGR. Perennial ryegrass and TF showed high tolerance to drought, salinity, and chilling temperatures (opt.-5 ºC and opt.-10 ºC), followed by CB, while KB, BER, and ZOY were stress sensitive. All grasses had increased DGR at opt.+5 ºC compared to the non-stress condition (opt.); however, DGR decreased as the temperatures further increased to opt.+10 ºC. Glycinebetaine seed priming only improved stress tolerance occasionally, suggesting that the efficacy of GB seed priming is concentration-, plant-, and stress-dependent.