Improved salt tolerance of medicinal plant Codonopsis pilosula by Bacillus amyloliquefaciens GB03

The plant growth promoting rhizobacterium (PGPR) strain Bacillus amyloliquefaciens GB03, an important soil-borne bacterium, was shown to promote growth and abiotic stress tolerance in Arabidopsis thaliana as well as in some crop plants. This study aimed to evaluate the effects of GB03 on salt tolerance in Codonopsis pilosula, a traditional Chinese medicinal herb that is sensitive to salinity. Twenty-day-old seedlings of C. pilosula were either inoculated with GB03 or without it (as a control). At the same time, plants were treated with NaCl (0, 50, 100, or 150 mM) for 40 days. Growth parameters, photosynthetic indexes, malondialdehyde concentration, and leaf osmotic potential were measured after treatments. The result indicated that GB03 improved plant biomass of C. pilosula under salt conditions and improved the photosynthetic capacity by increasing net photosynthetic rate and stomatal conductance and decreasing intercellular CO2 concentration under both 0 and 50 mM NaCl. The bacterium strain also decreased leaf osmotic potential and peroxidation of membrane lipids that could help the plant adapt to saline environments. This study provides insights into the application of selected bacteria in the culture of important Chinese herbal plants under mild salinity.