Effects of Bacillus methylotrophicus M4-1 on physiological and biochemical traits of wheat under salinity stress.

AIM: The aim of this study was to evaluate the ability of Bacillus methylotrophicus M4-1 to protect winter wheat from the harmful effects of soil salinity and alkalinity. METHODS AND RESULTS: We isolated the halotolerant B. methylotrophicus M4-1. Two representative soils with different salt contents (S1, 213 mus.cm(-1) ; S2, 786 mus.cm(-1) ) in the Yellow River delta region of China were selected for experiments. The effects of the M4-1 strain on the typical wheat variety (Jimai 21) in this environment were proven. In S1 soil, the M4-1 strain reduced the wheat rhizosphere soil pH (1.61%) and electrical conductivity (EC) (8.01%) and increased the exchangeable K content (11.14%). The uptake of Mg(2+) (20.73%) by wheat roots and K(+) (8.84%) by leaves was increased, and the content of Na(+) (23.62%) in leaves was reduced. In S2 soil, the M4-1 strain was able to reduce soil EC (2.56%) and increase exchangeable K (11.20%) content. The absorption of K(+) (13.28%) in wheat leaves was increased, and the content of Na(+) (12.41%) in roots was decreased. Total N and organic matter contents in rhizosphere soil were significantly positively correlated with wheat growth and salt tolerance, whereas EC showed a significant negative correlation. CONCLUSIONS: M4-1 attenuates salt stress injury in wheat under both low and high salt stress. SIGNIFICANCE AND IMPACT OF THE STUDY: We demonstrated the efficacy and value of plant growth-promoting rhizobacteria addition to protect winter wheat against salt stress and improve crop yield. We also elucidated the physicochemical and biochemical interactions among M4-1, the rhizosphere, and the host plant.