AUTHOR=Ma Qinghua , He Shanwen , Wang Xing , Rengel Zed , Chen Lin , Wang Xinghong , Pei Shunxiang , Xin Xuebing , Zhang Xiaoxia 

TITLE=Isolation and characterization of phosphate-solubilizing bacterium Pantoea rhizosphaerae sp. nov. from Acer truncatum rhizosphere soil and its effect on Acer truncatum growth

JOURNAL=Frontiers in Plant Science

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1218445

DOI=10.3389/fpls.2023.1218445

ISSN=1664-462X

ABSTRACT=<p>The <italic>Acer truncatum</italic> Bunge, widely distributed in North China, shows excellent tolerance to low-P soils. However, little information is available on potential phosphate-solubilizing bacterial (PSB) strains from the <italic>A. truncatum</italic> rhizosphere. The objectives of this work were to isolate and characterize PSB from <italic>A. truncatum</italic> rhizosphere soil and to evaluate the effect of inoculation with the selected strain on <italic>A. truncatum</italic> seedlings. The strains were characterized on the basis of phenotypic characteristics, carbon source utilization pattern, fatty acid methyl esters analysis, 16S rRNA gene and the whole-genome sequence. A Gram-negative and rod-shaped bacterium, designated MQR6<sup>T</sup>, showed a high capacity to solubilize phosphate and produce indole-3-acetic acid (IAA) and siderophores. The strain can solubilize tricalcium phosphate (TCP) and rock phosphate (RP), and the solubilization of TCP was about 60% more effective than RP. Phylogenetic analyses based on the 16S rRNA gene and whole-genome sequences revealed that strain MQR6<sup>T</sup> formed a distinct phyletic lineage as a new species within the genus <italic>Pantoea</italic>. The digital DNA-DNA hybridization value between strain MQR6<sup>T</sup> and the closely related strains was 19.5-23.3%. The major cellular fatty acids were summed feature 3 (C<sub>16:1</sub>ω7c and/or C<sub>16:1</sub>ω6c), summed feature 8 (C<sub>18:1</sub>ω6c and/or C<sub>18:1</sub>ω7c), C<sub>14:0</sub>, C<sub>16:0</sub>, and C<sub>17:0</sub> cyclo. Several genes related to IAA production, phosphonate transport, phosphate solubilization and siderophore biogenesis were found in the MQR6<sup>T</sup> genome. Furthermore, inoculation with the strain MQR6<sup>T</sup> significantly improved plant height, trunk diameter, dry weight and P accumulation in roots and shoot of <italic>A. truncatum</italic> seedlings compared to non-inoculated control. These plant parameters were improved even further in the treatment with both inoculation and P fertilization. Our results suggested that MQR6<sup>T</sup> represented a new species we named <italic>Pantoea rhizosphaerae</italic>, as a plant growth-promoting rhizobacterium that can solubilize inorganic P and improve growth of <italic>A. truncatum</italic> seedlings, emerging as a potential strategy to improve <italic>A. truncatum</italic> cultivation.</p>