Abstract: In this study, fresh peanut nodules were collected from seven major peanut growing areas in Hunan Province, and a total of 7 rhizobia strains were isolated and purified. The local peanut varieties Anhua small-seeded peanut and Changning small-seeded peanut varieties in Hunan Province were selected to test the capability of the 7 rhizobia strains by greenhouse pot inoculation experiments, and all 7 rhizobia strains could effectively form nodulation on the two peanut varieties, among which R3-2 and R4-6 showed the strongest nitrogen-fixing capability. Through 16S rDNA gene sequencing and sequence alignment, strain R3-2 was preliminarily identified as belonging to Bradyrhizobium japonicum. Further experiments demonstrated that the strain R3-2 had certain acid resistance and it grew well in modified Keyser and Munns medium while the pH is equal to 5.4 (including pH>5.4), and holding a certain tolerance to heavy metals. Finally, field experiments were carried out in the native environment of R3-2, and the results showed that peanut yield of the treatment group with 70% conventional nitrogen application and R3-2 rhizobia inoculation was the highest, which was 28.54% higher than that of the control group which is with conventional nitrogen application without rhizobia inoculation. With the fine effect on nitrogen fixation, as well as its positive tolerances on hydrogen ion and heavy metals, strain R3-2 is the potential rhizobium utilized in peanut cultivation in southern China.
Key words: Arachis hypogaea L.; Bradyrhizobium japonicum; tolerance of acids; yield; biological nitrogen fixation
（Acta Laser Biology Sinica, 2025, 34(1): 045-053）