Biochemical and Molecular Characterization of Potential Phosphate-Solubilizing Bacteria in Acid Sulfate Soils and Their Beneficial Effects on Rice Growth

Abstract

A study was conducted to determine the total microbial population, the occurrence of growth promoting bacteria and their beneficial traits in acid sulfate soils. The mechanisms by which the bacteria enhance rice seedlings grown under high Al and low pH stress were investigated. Soils and rice root samples were randomly collected from four sites in the study area (Kelantan, Malaysia). The topsoil pH and exchangeable Al ranged from 3.3 to 4.7 and 1.24 to 4.25 cmolc kg−1, respectively, which are considered unsuitable for rice production. Total bacterial and actinomycetes population in the acidic soils were found to be higher than fungal populations. A total of 21 phosphate-solubilizing bacteria (PSB) including 19 N2-fixing strains were isolated from the acid sulfate soil. Using 16S rRNA gene sequence analysis, three potential PSB strains based on their beneficial characteristics were identified (Burkholderia thailandensis, Sphingomonas pituitosa and Burkholderia seminalis). The isolated strains were capable of producing indoleacetic acid (IAA) and organic acids that were able to reduce Al availability via a chelation process. These PSB isolates solubilized P (43.65%) existing in the growth media within 72 hours of incubation. Seedling of rice variety, MR 219, grown at pH 4, and with different concentrations of Al (0, 50 and 100 µM) was inoculated with these PSB strains. Results showed that the bacteria increased the pH with a concomitant reduction in Al concentration, which translated into better rice growth. The improved root volume and seedling dry weight of the inoculated plants indicated the potential of these isolates to be used in a bio-fertilizer formulation for rice cultivation on acid sulfate soils.

Diversity and functional characterization of bacterial endophytes dwelling in various rice (Oryza sativa L.) tissues, and their seed-borne dissemination into rhizosphere under gnotobiotic P-stress

“…during 0P treatments. Inoculation of P-solubilizing bacteria has been reported to increase P-solubilization as well as rice growth (Panhwar et al 2011(Panhwar et al , 2014, which may partially explain the rhizospheric deployment of P-solubilizers by rice. The P-solubilizing rhizobacterial strains presently isolated have been found to be unique (as determined by 16S rRNA gene sequencing, data not shown) when compared to 52 shortlisted endophytic strains, which further corroborated both genetic complexity and diversity of endophytic taxa associated with rice.…”

Novel Technique to improve the pH of Acidic Barren Soil using Electrokinetic-bioremediation with the application of Vetiver Grass

“…al. [7] and Mohammadi [8] and other researchers in previous studies. Bioremediation is also a relatively simple technology compared to other techniques.…”

Applying Limestone or Basalt in Combination with Bio-Fertilizer to Sustain Rice Production on an Acid Sulfate Soil in Malaysia

“…Among the agronomic practices recommended to improve the fertility of acid sulfate soils acid sulfate soils are lime application [5], submergence, leaching, and application of manganese dioxide [6], application of basalt [7], or employment of bio-fertilizer [8,9]. Depending on the rate applied, adding lime or basalt to the soils would increase their pH.…”