Endophytic bacteria can mitigate salinity stress on seed germination and physiology in hybrid Pennisetum

Endophytic bacteria have a broad spectrum of applications such as in plant disease prevention, pest insect suppression, plant growth promotion, and plant salt and drought tolerance; they, therefore, provide a valuable natural resource. This investigation was conducted to determine the influence of the endophytic bacterium Pantoea sp. PP04 on seed germination and seedling growth of hybrid Pennisetum under low (100 mmol·L-1), medium (200 mmol·L-1), and high (300 mmol·L-1) salinity stress. The analysis showed that the endophyte PP04 had a significant positive impact on seed germination rate, germination index, and lengths of embryos under low and medium salinity stress, which would enhance their germination rate at 10.75%, 28.57%, and 300%, respectively. We also found that under different levels of salinity stress, this endophytic bacterium reduced lipid peroxidation of cell membranes in hybrid Pennisetum by inducing different antioxidant protective enzyme activities. As a consequence, the content of malondialdehyde (MDA) decreased. Under low and medium salinity stress, the endophytic bacterium significantly increased activity of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) in hybrid Pennisetum. The greatest increases in SOD (64.17%) and POD (73.14%) activities occurred under low salinity stress. The largest increases in CAT (160.57%) and APX (73.38%) occurred under high salinity stress. Our results indicated that the endophyte PP04 significantly mitigated the damage caused by oxidative stress from salinity and improved the tolerance of plants to a salt stress environment. These results suggest that the endophyte PP04 has promising characteristics for future applications.