Diversity and potassium-solubilizing activity of rhizosphere potassium-solubilizing bacteria of invasive Solidago canadensis.
Aims: Solidago canadensis, an invasive herbaceous species, has a strong capacity of potassium enrichment, that may relate to its influence on soil microbial community. Rhizosphere potassium-soluble bacteria can convert mineral potassium into soluble forms being able to be used by plants. It is not known how invasion of S. canadensis may affect diversity and potassium-solubilizing activity of the potassium-solubilizing bacteria. Methods: We compared S. canadensis and its coexisting native plant Imperata cylindrica in the reclaimed Hangzhou Bay wetland, Zhejiang Province. We compared the potassium contents of soil and the plant tissues of S. canadensis and Imperata cylindrica which coexists with the invasive species, the effect of potassium supply level on biomass accumulation of plants, and the quantity, diversity and potassium-soluble activity of the rhizosphere potassium-solubilizing bacteria. Important findings The potassium contents in stem and leaf of S. canadensis were significantly higher (1.59 and 7.33 times respectively) than that of I. cylindrica, the contents of available potassium in the 0-10 cm soil layer where the two species grew were significantly different, but not in the 10-20 cm soil layer. Potassium application experiments showed significant biomass increase in both S. canadensis and I. cylindrica, and tissue potassium concentrations as well. Potassium-dissolving medium culture results showed that the number of potassium-solubilizing bacteria of S. canadensis rhizosphere was 2.51 times higher than that of I. cylindrica. The strains with potassium-dissolving rings were identified, and the amount of released potassium was determined. Among the 15 strains of potassium-solubilizing bacteria isolated from the rhizosphere soil of S. canadensis, nine efficiently dissolved potassium, and the content of K+ in the treatment solution was 85.11%-192.54% higher than that in the control. Strain H2-20 had the strongest ability with the dissolved K+ of 10.657 mg.L-1. The potassium-solubilizing effect of rhizosphere potassium-solubilizing bacteria of S. canadensis was significantly higher than that of I. cylindrica. According to 16S rDNA identification, the 15 strains of bacteria associated with S. canadensis were of 11 genera, and 6 of them had been reported to have the potassium-solubilizing ability. Our results suggest that potassium-solubilizing bacteria in the rhizosphere of S. canadensis is abundant, and may play an important role in potassium enrichment.