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Plant roots significantly influence soil microbial diversity, and soil microorganisms play significant roles in both natural and agricultural ecosystems. Although the genetically modified (GM) crops with enhanced insect and herbicide resistance are thought to have unmatched yield and stress resistance advantages, thorough and in‐depth case studies still need to be carried out in a real‐world setting due to the potential effects of GM plants on soil microbial communities. In this study, three treatments were used: a recipient soybean variety Jack, a triple transgenic soybean line JD321, and the glyphosate‐treated JD321 (JD321G). Three sampling stages (flowering, seed filling and maturing), as well as three host niches of soybean rhizosphere [intact roots (RT), rhizospheric soil (RS) and surrounding soil (SS)] were established. In comparison to Jack, the rhizospheric soil of JD321G had higher urease activity and lower nitrite reductase at the flowering stage. Different treatments and different sampling stages existed no significant effects on the compositions of microbial communities at different taxonomic levels. However, at the genus level, the relative abundance of three plant growth‐promoting fungal genera (i.e. Mortierella, Chaetomium and Pseudombrophila) increased while endophytic bacteria Chryseobacterium and pathogenic bacteria Streptomyces decreased from the inside to the outside of the roots (i.e. RT → RS → SS). Moreover, two bacterial genera, Bradyrhizobium and Ensifer were more abundant in RT than in RS and SS, as well as three species, Agrobacterium radiobacter, Ensifer fredii and Ensifer meliloti, which are closely related to nitrogen‐fixation. Furthermore, five clusters of orthologous groups (COGs) associated to nitrogen‐fixation genes were higher in RT than in RS, whereas only one COG annotated as dinitrogenase iron‐molybdenum cofactor biosynthesis protein was lower. Overall, the results imply that the rhizosphere host niches throughout the soil–plant continuum largely control the composition and function of the root‐associated microbiome of triple transgenic soybean. [ABSTRACT FROM AUTHOR]

Changes in root exudates and rhizospheric microbial functional capacities involved in carbon (C) decomposition and nitrogen (N) transformation of aluminum (Al)-tolerant and Al-sensitive soybean genotypes were investigated under Al stress. Rhizosphere soils were collected from rhizobox systems with two soybean genotypes. A wide range of microbial functional capacities were determined by functional gene arrays. Microbial functional capacities of rhizospheres were distinct between Al-tolerant and Al-sensitive genotypes, which were related to exchangeable Al concentrations. Functional capacities associated with decomposition of chemically recalcitrant C were lower in Al-tolerant than Al-sensitive genotypes, which was negatively correlated with the secretion rate of succinic acid. Microbial functional capacities were higher for nitrification but lower for denitrification in the rhizosphere of Al-tolerant than Al-sensitive genotype, which coincided with higher succinic acid secretion and lower abundance of microbial oxygen stress genes. Soybean biomass increased logarithmically with nitrification capacities. We concluded that exchangeable Al concentrations, root exudation, and microbial C and N cycling capacities were intrinsically linked, which served as a key mechanism for legume genotypes toward enhancing tolerance to Al stress occurring in acid soils. [ABSTRACT FROM AUTHOR]

Abstract: Aluminum (Al) is one of the limiting factors for crop production in acidic soil. We aimed to demonstrate how the rhizosphere diazotrophic community responds to two contrasting soybean genotypes, BX10 (Al-tolerant) and BD2 (Al-sensitive), under Al stress at different growth stages. The diversity and abundance of nifH gene in the rhizosphere soils were assessed by denaturing gradient gel electrophoresis (DGGE) and real-time PCR. The results indicated that there were differences in the community structure between BX10 and BD2 at three sampling stages, respectively. Phylogenetic analyses revealed that 3 and 16 non-identical sequences were responsive to BX10 and BD2, respectively, during the whole growth periods. Parts of sequences responsive to BD2 were affiliated with Rhizobium sp. and Azospirillum brasilense, which have the potential to promote plant growth. Dominant diazotrophs varied in different growth stages of both soybean genotypes. Higher nifH abundance was observed in BD2 at seedling stage, whereas that was detected in BX10 at flowering and maturity stages. The diazotrophic community is sensitive and responds differentially to different soybean genotypes adapted to Al stress, as demonstrated by the increased quantity of diazotrophs in BX10 and the stimulation of beneficial diazotrophic bacteria in BD2. [Copyright &y& Elsevier]

A total of 210 soybean samples collected from different areas of Heilongjiang Province were analyzed by PCR to detect the presence of RR (Roundup Ready) soybean ingredient. Results showed that CaMV35S promoter was not detected in all samples. CP4-EPSPS gene was amplified in 13 samples, but all of them were proved to be false positives in restriction endonuclease digestion analysis of PCR products. Further analysis by nested PCR indicated that there were no RR soybean ingredients in the samples. Besides, the amplified fragments of 0x1 by CP4-EPSPS primers were sequenced, and the results confirmed again the fact that this fragment was not from CP4-EPSPS gene. [ABSTRACT FROM AUTHOR]