Soil salinity has adverse effects on soil microbial activity and nutrient cycles and therefore limits crop growth and yield. Amendments with halotolerant phosphate-solubilizing bacteria (PSB) and rock phosphate (RP) may improve properties of saline soil. In this study, we investigated the effects of RP either alone or in combination with PSB (Providencia rettgeri strain TPM23) on peanut growth and soil quality in a saline soil. With the combined application of RP and PSB, plant length and biomass (roots and shoots) and uptake of phosphorus (P), nitrogen (N), and potassium (K) increased significantly. Soil Na⁺ and Cl^– contents decreased in the PR alone or PR combined with PSB treatment groups. There were strongly synergistic effects of RP and PSB on soil quality, including a decrease in pH. The soil available N, P, and K contents were significantly affected by the PSB treatments. In addition, the alkaline phosphomonoesterases, urease, and dehydrogenase activities increased significantly compared with the untreated group; highest alkaline phosphomonoesterases activity was observed in the RP and PSB treatment groups. The composition of rhizosphere soil bacterial communities was determined using 454-pyrosequencing of the 16S rRNA gene. In the PR alone or PR combined with PSB treatment groups, the structure of the soil bacterial community improved with increasing richness and diversity. With PSB inoculation, the relative abundance of Acidobacteria, Chloroflexi, and Planctomycetes increased. The three phyla were also positively correlated with soil available N and root dry weight. These results suggested microbiological mechanisms by which the combined use of RP and PSB improved saline soil and promoted plant growth. Overall, the study indicates the combined use of RP and PSB can be an economical and sustainable strategy to increase plant growth in P-deficient and salt-affected soils.

In search of efficient salt-tolerant phosphate solubilizing bacteria (PSB), we conducted a survey of PSB that naturally colonize the rhizosphere of peanuts in Xinjiang, China, a typical inland saline area. A total of 23 PSB were isolated, which included 12 Bacillus strains, three Acinetobacter strains, two Pseudomonas strains, two Brevibacillus, and one strain of Gordonia terrae, Chryseobacterium lathyri, Ensifer sesbaniae, and Paenibacillus illinoisensis. All PSB have high potential for dissolving calcium phosphate [Ca₃(PO₄)₂] within the range of 65–496 mg·L⁻¹, but relatively weak ability to dissolve AlPO₄ in amounts ranging from 0.4 to 11.4 mg·L⁻¹, FePO₄ ranging from 0.1 to 5.5 mg·L⁻¹, and lecithin ranging from 2.1 to 10.3 mg·L⁻¹. The maximum tolerance for pH is 10, and the maximum tolerance for Na₂CO₃ is 50 mm. Six isolates that can grow under the condition of 1.5 M NaCl (YMX5, YMX11, TPMX5, TPMX16, TPMX18, and TPMX19) were selected to determine their ability to dissolve Ca₃(PO₄)₂ and tolerate pH changes. This study characterized salt-tolerant PSB isolates that can be used as bioinoculants to protect plants against salt stress. In addition, we describe the phosphate-solubilizing ability of Gordonia terrae at high NaCl concentrations.

Late embryogenesis abundant (LEA) proteins generally accumulate in seeds during the later stages of maturation. However, LEA proteins also accumulate in response to abiotic stressors, particularly those involving cellular dehydration. LEA genes have been well-characterized in many plant species, but not in peanut. Here we studied the LEA genes in two wild peanut species (Arachis duranensis and Arachis ipaensis) in an effort to create a genetic resource for peanut crop improvement. Specifically, we examined AdLEA and AiLEA sequence characteristics, gene structure, evolutionary relationships, chromosomal localization, promoter cis-acting elements, and expression patterns in different tissues under low temperature, salinity, drought, and ABA stress. In all, we identified 65 AdLEA and 69 AiLEA genes representing all 8 LEA subfamilies, which were unevenly distributed across all 10 peanut chromosomes. The majority of LEA proteins were found to be highly hydrophilic. MEME analysis indicated that LEA gene motifs were conserved within groups, but not between groups. The LEA genes contained a diverse array of stress- and phytohormone-responsive cis-acting elements, with the AdLEA2-20 and AiLEA2-20 genes containing the greatest number of elements. Both AdLEA2-20 and AiLEA2-20 were upregulated in response to cold temperatures, drought, salinity, and ABA-exposure, although the dynamics were tissue-dependent. This study lays the foundation for future studies on the LEA gene family and abiotic stress in peanut, and our results will be invaluable for the genetic improvement of peanut by characterizing the genetic resources of wild peanut species.