Isolation and efficient strain screening of microorganisms from peanut rhizosphere

Abstract:

[Background] The rhizosphere soil harbors diverse microorganisms. The isolation and screening of efficient strains with different functions is the premise for the development of efficient composite microbial fertilizers. [Objective] To isolate microorganisms from the rhizosphere soil and root surface of peanut and screen out efficient strains with organic and inorganic phosphorus-solubilizing, indole-3-acetic acid (IAA)-producing, and siderophore-producing functions, so as to lay a foundation for the research and development of microbial fertilizers for peanut. [Methods] The dilution-plate coating method was employed to isolate the microorganisms from the peanut rhizosphere soil and root surface samples collected from Qixia City, Pingdu City, and Laishan district of Yantai City in Shandong Province. The microorganisms were identified by the phylogenetic analysis based on the 16S rRNA gene sequences. The strains with efficient organic and inorganic phosphorus-solubilizing, IAA-producing, and siderophore-producing functions were obtained through primary and secondary screening. [Results] A total of 147 strains were isolated, purified, and preserved in this study, including 75 strains isolated from the rhizosphere soil samples and 72 strains from the root surface samples. The isolates belonged to 40 genera of 4 phyla including Actinomycetota, Bacillota, Bacteroidota, and Pseudomonadota. Streptomyces (21.77%) and Bacillus (16.33%) were the dominant genera. The root surface samples had higher alpha diversity of microbial community than the rhizosphere samples. Among the 62 strains with organic phosphorus-solubilizing ability, Brevundimonas sp. YTU21021 showed the highest activity of 1.12 mg/L. Among the 31 strains with inorganic phosphorus-solubilizing ability, Acinetobacter sp. YTU21009 showed the highest activity of 7.04 mg/L. Among the 63 strains that could produce IAA, Enterobacter sp. YTU21054 showed the highest yield of 184.19 mg/L. Among the 7 strains capable of producing siderophores, Burkholderia sp. YTU21051 presented the highest efficiency with the A_s/A_r ratio of 0.9. [Conclusion] There are diverse culturable microorganisms in the rhizosphere and root surface samples of peanut. The efficient functional strains obtained in this study enrich the functional microbial resources in peanut rhizosphere and lay a foundation for the development of composite microbial fertilizers with efficient rhizobia for peanut.