Abstract:[Objective] We previously isolated bacterial strains from winter wheat habitats, now, we will screen cold tolerant strains from those isolates and assess their plant growth-promoting potential. [Methods] we screened cold tolerant strains on nutrient agar plates incubated at 4 °C, determined these cold tolerant strains’ plant growth-promoting attributes such as indole-3-acetic acid (IAA) production, 1-aminocyclopropane-1-carboxylate (ACC) deaminase production, inorganic and organic phosphate solubilization and siderophores production, selected strains with good potential according to the assessment system established here, and then tested their plant biomass increase effects at different temperatures based on bioassay experiments. [Results] We screened 34 cold tolerant strains from those isolates. For the selected 8 strains with good potential, the correlation coefficiency indicating coincident relationship between the assessed growth promoting potential and the increase effect on plants in greenhouse condition was more than 0.62. Among them, 1bYB22 and 3bJN2 exhibited more than 28% increase effect on shoot weights of cucumber incubated at 28 °C, and seed bacterization with 1bYB22 and 3bJN2 also increased non-heading Chinese cabbage’s root lengths with 116.76% and 46.82% at 15 °C, respectively. And 1bYB22 exhibited 25.11% increase effect on shoot weights of non-heading Chinese cabbage incubated at 15 °C. Field testing of the 1bYB22 inoculum in wheat also showed significant increase in growth and yield. [Conclusion] Through the screening system established in this study, we obtained cold tolerant P. fluorescens strains 1bYB22 and 3bJN2 from wheat habitat isolates, and these two bacterial strains both exhibited plant growth-promoting effect at 15 °C and 28 °C and promoted the growth of wheat in the field.
