Abstract: Alkaline stress leads to severe crop loss. Inoculation of ACC-deaminase-containing rhizobacteria can improve plant resistance to several abiotic stresses,however,little research has been done on whether such bacteria can improve plant resistance to alkalinity. Using the ACC deaminase-containing rhizobacteria Variovorax paradoxus 5C-2 and Glycine max（L.）Merr. Huang 13 as the experimental materials,we studied the effects of the inoculation of V. paradoxus 5C-2 on the growth of soybean under alkali stress. The results showed that 40 mmol/L NaCl treatment presented no effect on soybean growth,but at 16 d after treated with alkaline salts（pH values 8.12 and 9.04,respectively）containing 40 mmol/L Na⁺,the biomass of soybean aboveground and root,total lateral root length,chlorophyll content and photosynthetic efficiency dramatically reduced,while stomatal resistance significantly increased. After inoculation of the rhizobacteria,the dry weight of shoot and root increased. Under the condition of pH 9.04,the total lateral root length,chlorophyll content and maximum photosynthetic potential of soybean increased clearly after the inoculation,and stomatal resistance decreased significantly. These experimental results demonstrated that,under the high pH condition,inoculation of rhizospheric bacteria V. paradoxus 5C-2 may alleviate the stress effects of alkaline salts on soybean plant.

Key words: alkaline stress, ACC deaminase, soybean, growth-promoting rhizobacteria