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

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

doi:10.3389/fpls.2023.1218445

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

Front Plant Sci. 2023 Jul 14:14:1218445. doi: 10.3389/fpls.2023.1218445. eCollection 2023.

Authors

Qinghua Ma^{1

2}, Shanwen He³, Xing Wang⁴, Zed Rengel^{5

6}, Lin Chen¹, Xinghong Wang¹, Shunxiang Pei¹, Xuebing Xin¹, Xiaoxia Zhang⁴

Affiliations

¹ Experimental Centre of Forestry in North China, National Permanent Scientifc Research Base for Warm Temperate Zone Forestry of Jiulong Mountain, Chinese Academy of Forestry, Beijing, China.
² State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry, Beijing, China.
³ Key Laboratory of National Forestry and Grassland Administration on Ecological Landscaping of Challenging Urban Sites, Shanghai Academy of Landscape Architecture Science and Planning, Shanghai, China.
⁴ State Key Laboratory of Efficient Utilization of Arid and Semi-arid Arable Land in Northern China, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing, China.
⁵ UWA School of Agriculture and Environment, The University of Western Australia, Perth, WA, Australia.
⁶ Institute for Adriatic Crops and Karst Reclamation, Split, Croatia.

Abstract

The Acer truncatum 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 A. truncatum rhizosphere. The objectives of this work were to isolate and characterize PSB from A. truncatum rhizosphere soil and to evaluate the effect of inoculation with the selected strain on A. truncatum 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^T, 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^T formed a distinct phyletic lineage as a new species within the genus Pantoea. The digital DNA-DNA hybridization value between strain MQR6^T and the closely related strains was 19.5-23.3%. The major cellular fatty acids were summed feature 3 (C_16:1ω7c and/or C_16:1ω6c), summed feature 8 (C_18:1ω6c and/or C_18:1ω7c), C_14:0, C_16:0, and C_17:0 cyclo. Several genes related to IAA production, phosphonate transport, phosphate solubilization and siderophore biogenesis were found in the MQR6^T genome. Furthermore, inoculation with the strain MQR6^T significantly improved plant height, trunk diameter, dry weight and P accumulation in roots and shoot of A. truncatum 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^T represented a new species we named Pantoea rhizosphaerae, as a plant growth-promoting rhizobacterium that can solubilize inorganic P and improve growth of A. truncatum seedlings, emerging as a potential strategy to improve A. truncatum cultivation.

Keywords: Acer truncatum; P accumulation; Pantoea; genome; phosphate-solubilizing bacteria.

Grants and funding

This study was supported by the Science Foundation of the Chinese Academy of Forestry (CAFYBB2020ZB005) and the Agricultural Science and Technology Innovation Program (ASTIP No. CAAS-ZDRW202201).