The diversity and community structure of rhizospheric microbes are largely affected by soil physicochemical properties and plant species. In this work, high throughput sequencing and quantitative real-time PCR targeting nifH gene were used to assess the abundance and diversity of diazotrophic community in the coastal saline soils of Yellow River Delta (YRD). We demonstrated that the copy number of nifH gene encoding the Fe protein subunit of the nitrogenase in the nitrogen fixation process was significantly affected by soil physiochemical factors, and the abundance of diazotrophs in the rhizospheric soil samples collected from different locations was positively related with soil physicochemical properties. Soil salinity (P=0.003) and moisture (P=0.003) were significantly co-varied with the OTU-based community composition of diazotrophs. Taxonomic analysis showed that most diazotrophs belonged to the Alphaproteobacteria, Gammaproteobacteria and Deltaproteobacteria. Linear discriminant analysis (LDA) effect size (LEfSe) and canonical correspondence analysis (CCA) showed that diazotrophic community structure significantly varied with soil salinity, moisture, pH and total nitrogen, carbon, sulphur and nitrite (NO₂^–N) content. Our findings provide direct evidence toward the understanding of different effects of soil physicochemical properties and host plant traits such as halophytes types, life span and cotyledon type, on the community composition of diazotrophic populations in the rhizosphere of plants grown in coastal saline soils.

Peanut productivity is severely restricted by soil salinization and associated nutrient deficiency in saline soil. The quinoa–peanut relay intercrop pattern (IP) is a promising planting system that utilizes the biological advantages of quinoa to improve soil ecological functions and productivity. However, the effects of IP on soil physicochemical and biological properties and the yield formation of the combined peanut crop are still unclear. Two-year field experiments in coastal saline soil were conducted to explore the effects of IP on peanut growth and pod yield, soil physicochemical properties, and microbial community characterization at different growth stages of peanut based on the traditional monocrop pattern (MP). The results show that IP promoted peanut pod yield, although there was the disadvantage of plant growth at an early stage. Soil water content, electrical conductivity (EC), and Na⁺ content in the peanut rhizosphere were lower, whereas K⁺, NH₄⁺, and total organic carbon (TOC) contents were higher in IP systems at both the vegetative and reproductive stages. The pod yield of peanut was significantly negatively correlated with soil EC and Na⁺ contents at the vegetative stage, but positively correlated with K⁺, NO₃⁻, NH₄⁺, PO₄³⁻, and TOC contents at the reproductive stage. IP rebuilt the composition of the soil bacterial community in the peanut rhizosphere and increased the abundance of the beneficial bacterial community, which were positively correlated with soil TOC, K⁺, NH₄⁺, NO₃⁻, and PO₄³⁻ contents. These findings suggest that IP can increase peanut pod yield through optimizing soil physicochemical properties and microbial community composition, and it is a promising planting system for improving agricultural production in coastal saline lands.

Soil salinization has become a major environmental factor severely threatening global food security. The application of porous minerals could significantly ameliorate soil fertility and promote plant productivity under salt stress conditions. However, the effects of porous minerals on improving the salt resistance of grain crops in coastal saline soils is not fully studied. In this work, the shoot growth and grain yield of wheat plants grown in coastal saline fields, respectively amended with the four naturally available porous minerals, diatomite, montmorillonite, bentonite and zeolite, were assessed. The application of porous minerals, especially zeolite, significantly improved the biomass and grain yield of wheat plants under saline conditions, as demonstrated by the augmented plant fresh mass (14.8~61.2%) and increased seed size (3.8~58.8%) and number (1.4~57.5%). Soil property analyses exhibited that porous-mineral amendment decreased soil sodium content and sodium absorption ratio, and increased soil nutrients in both the rhizosphere and nonrhizosphere of wheat plants. Further quantitative-PCR and 16S high-throughput sequencing analysis revealed that porous-mineral application also remarkably increased the abundance of bacterial 16S rRNA (0.8~102.4%) and fungal 18S rRNA (89.2~209.6%), and altered the composition of the soil microbial community in the rhizosphere of wheat. Our findings suggest that zeolite could be used as an ideal salt soil amendment, and the changes in soil properties and microorganisms caused by the application of porous minerals like zeolite improved the salt resistance of wheat plants in coastal saline land, leading to increased shoot growth and seed production.

Quinoa (Chenopodium quinoa Willd.) has been widely grown as a cash crop. However, the molecular mechanism by which it responds to cold stress at the seed germination stage is still largely unknown. In this study, we performed a comparative transcriptomic analysis between the cold-tolerant cultivar XCq and cold-sensitive cultivar QCq in response to cold stress. A total number of 4552 and 4845 differentially expressed genes (DEGs) were identified in XCq and QCq upon the treatment of cold stress, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis demonstrated that the mitogen-activated protein kinase (MAPK) signaling pathway was identified only among the up-regulated DEGs in XCq.The expression of DEGs, which encoding transcription factors, such as AP2/ERF, bHLH, bZIP, MYB, ICEs, and CORs related to cold response, were higher in XCq than in QCq in response to cold stress. Weighted gene co-expression network analysis (WGCNA) showed that DEGs clustered in the co-expression modules positively correlated with the factors of quinoa variety and temperature were significantly enriched in the oxidative phosphorylation metabolic pathway. Further physiochemical analyses showed that the activities of superoxide dismutase and peroxidase as well as the contents of soluble protein and sugar, were significantly higher in XCq than in QCq. In summary, MAPK signaling and oxidative metabolism were the key pathways in quinoa upon cold stress. Our findings revealed that the enhanced activities of antioxidant enzymes alleviate the lipid peroxidation of membranes and promote the accumulation of osmotic adjustment substances, thereby enabling seeds to better resist oxidative damage under cold stress.

Halophyte plants could successfully survive in severe saline lands. However, the spatiotemporal responses of halophyte trees to salt stress are still largely unclear. Here, comprehensive transcriptome profiling analyses in the roots of T. chinensis tree in response to salt stress were conducted. After treatments with 300 mM NaCl for 12, 24 and 48 h, 4452, 4836 and 5222 differentially expressed genes (DEGs) were respectively identified. Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis indicated that these DEGs identified at different treatment times were enriched in the same pathways. Further transcriptomic analyses demonstrated that gene encoding transcription factor genes, such as bHLH, Dof, MYB and NAC, and oxidative stress and sugar metabolism related genes, were differentially and time specifically expressed, especially at the time point of 12 h treatment. The results of this study will provide fundamental information for future study on the mechanism of halophyte plants in response to salt stress, and for the identification of new candidates genes usable for the molecular breeding of plant varieties with promoted tolerance to abiotic stress.