Abstract
Phosphorus in the soil accessible to plants can easily be combined with calcium ion, the content of which is high in karst rocky desertification (KRD) regions, thereby resulting in a low utilization efficiency of phosphorus. The application of phosphate-solubilizing bacteria (PSB) from the KRD region would facilitate enhanced phosphate availability in the soil. In the present study, the strains belonging to Acinetobacter, Paraburkholderia, and Pseudomonas with efficient phosphate-solubilizing ability were isolated from fruit tree rhizosphere soils in KRD regions. Particularly, Acinetobacter sp. Ac-14 had a sustained and stable phosphate-solubilizing ability (439–448 mg/L, 48–120 h). Calcium carbonate decreased the phosphate-solubilizing ability in liquid medium; however, it did not affect the solubilization index in agar-solidified medium. When cocultivated with Arabidopsis thaliana seedling, Ac-14 increased the number of lateral roots, fresh weight, and chlorophyll content of the seedlings. Metabolomics analysis revealed that Ac-14 could produce 23 types of organic acids, majorly including gluconic acid and D-(-)-quinic acid. Expression of Ac-14 glucose dehydrogenase gene (gcd) conferred Pseudomonas sp. Ps-12 with a sustained and stable phosphate-solubilizing ability, suggesting that the production of gluconic acid is an important mechanism that confers phosphate solubilization in bacteria. Moreover, Ac-14 could also produce indole acetic acid and ammonia. Collectively, the isolated Ac-14 from KRD regions possess an efficient phosphate-solubilizing ability and plant growth-promoting effect which could be exploited for enhancing phosphorus availability in KRD regions. This study holds significance for the improvement of soil fertility and agricultural sustainable development in phosphorus-deficient KRD regions.
Highlights
There are three karst centers worldwide: in the European Mediterranean, the Dinaric karst regions of the Balkan Peninsula, and in Southwest China
805 phosphate-solubilizing bacteria (PSB) strains were isolated from 18 fruit tree rhizosphere soil samples
570 PSB strains were from karst rocky desertification (KRD) regions in Southwest China, and 235 PSB strains were from the NKRD regions (Table 1)
Summary
There are three karst centers worldwide: in the European Mediterranean, the Dinaric karst regions of the Balkan Peninsula, and in Southwest China. The processes of soil erosion, vegetation loss, exposure of rocks, and the appearance of a rocky landscape are termed as karst rocky desertification (KRD, Wang et al, 2004; Jiang et al, 2014). A Bacterium Has Phosphate-Solubilizing Ability most severe ecological problems worldwide (Wang et al, 2004; Tang et al, 2019). Bare carbonate rocks generally produce Ca2+ and HCO3− in soil (White, 1997), wherein Ca2+ can combine with H2PO4− to form insoluble phosphate, which is inaccessible for plants
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