Understanding salinity tolerance mechanisms and strategic seedhead suppression in bermudagrass

Turfgrass managers across the United States are increasingly challenged by rising salinity in water and soil. These challenges are compounded by government mandates requiring the use of low-quality, secondary water sources for irrigation, which drives the urgent need for salt-tolerant turfgrasses. Additionally, seedheads significantly reduce the aesthetic value and functional performance of turfgrass, particularly in high-maintenance areas such as putting greens. To address these issues, our study aimed to evaluate salinity tolerance and seedhead suppression in bermudagrass through two controlled-environment studies and one field study. The first greenhouse study included six bermudagrass genotypes (17×3, 12×19, 13×12, accession 1, accession 2, and 'Premier'). The second study focused exclusively on 'Tifway' bermudagrass. Both studies subjected the plants to three salinity treatments with electrical conductivity (EC) levels of 1.5, 15, and 30 dS m⁻¹ for eight weeks. Bermudagrass performance was evaluated through various parameters, including turf quality (TQ), normalized difference vegetation index (NDVI), vertical shoot growth (VSG), percent green coverage (GC), tissue sodium (Na⁺) concentration, relative salt gland Na⁺ excretion rate, root dry weight (RDW), and leaf salt gland density (SGD, for the first study only).In the first study, the experimental genotypes demonstrated superior salinity tolerance, maintaining acceptable turf quality at 30 dS m⁻¹. 'Premier' declined significantly under high salinity, while 17×3 showed the highest SGD and 12×19 exhibited the highest Na⁺ excretion from leaf salt glands, indicating robust salinity tolerance. Accession 2 and 'Premier' exhibited reduced RDW at 30 dS m⁻¹, whereas the experimental genotypes and accession 1 showed an increase, suggesting adaptive root growth under stress. Regarding the impact of Civitas™, its application at 1.43 mL m⁻² improved turfgrass health under non-saline conditions. However, higher application rates (2.71 mL m⁻²) exacerbated stress under salinity levels of 15 and 30 dS m⁻¹. The field study focused on seedhead suppression using four plant growth regulators (PGRs): trinexapac-ethyl (TE; Primo Maxx), ethephon (Proxy), prohexadione calcium (Anuew), paclobutrazol (Trimmit), and an untreated control. PGRs were applied biweekly before, during, and after the seedhead season on 'OKC3920' bermudagrass. Ethephon effectively delayed seedhead production during peak spring periods but led to reduced-intensity seedhead emergence in the summer and early fall. Paclobutrazol and TE promoted earlier green-up, though paclobutrazol was associated with temporary phytotoxicity. Overall, the salt-tolerant genotypes offer a potential solution for maintaining turfgrass quality and functionality under mild saline conditions. Further research is recommended to optimize strategies for effective seedhead suppression, ensuring maximum benefits for turfgrass managers.