AUTHOR=Zou Lan , Wang Qian , Li Muyi , Wang Siyu , Ye Kunhao , Dai Wei , Huang Jing 

TITLE=Culturable bacterial endophytes of Aconitum carmichaelii Debx. were diverse in phylogeny, plant growth promotion, and antifungal potential

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1192932

DOI=10.3389/fmicb.2023.1192932

ISSN=1664-302X

ABSTRACT=<p>Medicinal plants harbor tremendously diverse bacterial endophytes that maintain plant growth and health. In the present study, a total of 124 culturable bacterial endophytes were isolated from healthy <italic>Aconitum carmichaelii</italic> Debx. plants. These strains were clustered into 10 genera based on full-length 16S rDNA sequences, among which <italic>Bacillus</italic> and <italic>Pseudomonas</italic> were the dominant genera. In addition, <italic>A. carmichaelii</italic> may capture 10 potential new bacterial species based on multi-locus sequence analysis of three housekeeping genes (<italic>gyrA, rpoB</italic>, and <italic>atpD</italic>). The majority of these bacterial endophytes exhibited plant growth-promoting ability through diverse actions including the production of either indole acetic acid and siderophore or hydrolytic enzymes (glucanase, cellulose, and protease) and solubilization of phosphate or potassium. A total of 20 strains inhibited hyphal growth of fungal pathogens <italic>Sclerotium rolfsii</italic> and <italic>Fusarium oxysporum in vitro</italic> on root slices of <italic>A. carmichaelii</italic> by the dual-culture method, among which <italic>Pseudomonas</italic> sp. SWUSTb-19 showed the best antagonistic activity. Field experiment confirmed that <italic>Pseudomonas</italic> sp. SWUSTb-19 significantly reduced the occurrence of southern blight and promoted plant biomass compared with non-inoculation treatment. The possible mode of actions for <italic>Pseudomonas</italic> sp. SWUSTb-19 to antagonize against <italic>S. rolfsii</italic> involved the production of glucanase, siderophore, lipopeptides, and antimicrobial volatile compounds. Altogether, this study revealed that <italic>A. carmichaelii</italic> harbored diverse plant growth-promoting bacterial endophytes, and <italic>Pseudomonas</italic> sp. SWUSTb-19 could be served as a potential biocontrol agent against southern blight.</p>