Impact of PGPR on germination and seedling vigor of cool- and warm-season forage grasses under different temperature regimes

Authors: SATOGNON, FELIX - Auburn University; Watts, Dexter; Adesemoye, Anthony; Torbert Iii, Henry; PRASAD, RISHI - Auburn University; MULLENIX, M. KIMBERLY - Auburn University

Submitted to: Arid Land Research and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Plant growth-promoting rhizobacteria (PGPR) are free-living bacteria living around the plant roots that are known for improving plant growth and decreasing plant stress. The objective of this study was to determine whether the addition of these PGPR to plant seeds can increase the rate of germination and seedling growth of four grasses – ryegrass (cool season grass), tall fescue (cool season grass), bahiagrass (warm season grass), and bermudagrass (warm season grass) - under different temperature conditions. A mixture of four PGPR bacterial trains were used for this experiment including Bacillus altitudinis AP18, B. subtilis AP278, B. safensis AP280, and Lysinibacillus macroides AP282 and evaluated at 21°C, high: 32°C for 14 days. Results showed that temperature significantly influenced germination rates. Ryegrass had minimal influence to temperature, while tall fescue germination rate decreased at the high temperature. In contrast, bahiagrass and bermudagrass had higher germination rates at the high temperatures. PGPR inoculation did not influence germination. However, it did improve seedling growth with the PGPR-treated seedlings having faster leaf development. More work is needed to determine whether inoculation of PGPR would be more effective applied with the seed or after seedling emergence.

Technical Abstract: Plant growth-promoting rhizobacteria (PGPR) are well-known for their ability to enhance plant growth and protect plants from various stresses, including temperature extremes. The objective of this study was to investigate the impact of PGPR inoculation on the germination and seedling vigor of four grasses - ryegrass (Lolium perenne), tall fescue (Lolium arundinaceum), bahiagrass (Paspalum notatum) and bermudagrass (Cynodon dactylon) - under two different temperature conditions. The study was 2x2 factorial experiment with two temperature regimes (low: 21°C, high: 32°C) and two inoculation treatments, consisting of PGPR mixture or without. The experiments were run for 14 days. Results showed that temperature significantly influenced germination rates. Ryegrass had limited sensitivity to temperature, while tall fescue germination rate decreased at higher temperatures. In contrast, bahiagrass and bermudagrass exhibited higher germination rates at the high temperatures. While PGPR inoculation did not positively influence germination, it significantly enhanced seedling vigor of the ryegrass and tall fescue, even at the higher temperature. PGPR-treated seedlings had faster leaf development, with significant effects being observed for second leaf development compared to the control. To optimize the benefits of PGPR on forage grass establishment, strategies such as applying PGPR after seedling emergence may be considered.