Soil with low phosphorus (P) availability and organic matter contents exists in large area of southwest of China, but some soybean genotypes still show well adaptations to this low yield farmland.  However, to date, the underlying mechanisms of how soybean regulates soil P availability still remains unclear, like microbe-induced changes.  The objective of the present study was to compare the differences of rhizosphere bacterial community composition between E311 and E109 in P-sufficiency (10.2 mg kg^–1) and P-insufficiency (5.5 mg kg^–1), respectively, which then feedback to soil P availability.  In P-sufficiency, significant differences of the bacterial community composition were observed, with fast-growth bacterial phylum Proteobacteria, genus Dechloromonas, Pseudomonas, Massilia, and Propionibacterium that showed greater relative abundances in E311 compared to E109, while in P-insufficiency were not.  A similar result was obtained  that E311 and E109 were clustered together in P-insufficiency rather than in P-sufficiency by using principal component analysis and hierarchical clustering analysis.  The quadratic relationships between bacterial diversity and soil P availability in rhizosphere were analyzed, confirming that bacterial diversity enhanced the soil P availability.  Moreover, the high abundance of Pseudomonas and Massilia in the rhizosphere of E311 might increased the P availability.  In the present study, the soybean E311 showed capability of shaping rhizosphere bacterial diversity, and subsequently, increasing soil P availability.  This study provided a strategy for rhizosphere management through soybean genotype selection and breeding to increase P use efficiency, or upgrade middle or low yield farmland.

To clarify how shade stress affects lignin biosynthesis in soybean stem, two varieties, Nandou 12 (shade tolerant) and Nan 032-4 (shade susceptible) grew under normal light and shade conditions (the photosynthetically active radiation and the ratio of red:far-red were lower than normal light condition).  Lignin accumulation, transcripts of genes involved in lignin biosynthesis, and intermediates content of lignin biosynthesis were analyzed.  Both soybean varieties suffered shade stress had increased plant heights and internode lengths, and reduced stem diameters and lignin accumulation in stems.  The expression levels of lignin-related genes were significantly influenced by shade stress, with interactions between the light environment and variety.  The gene of 3-hydroxylase (C3H), cinnamoyl-CoA reductase (CCR), caffeoyl-CoA O-methyltransferase (CCoAOMT), and peroxidase (POD) attributed to lignin biosynthesis under shade stress, and the down-regulation of these genes resulted in lower caffeic, sinapic, and ferulic acid levels, which caused a further decrease in lignin biosynthesis.  Under shade stress, the shade tolerant soybean variety (Nandou 12) showed stiffer stems, higher lignin content, and greater gene expression level and higher metabolite contents than shade susceptible one.  So these characteristics could be used for screening the shade-tolerant soybean for intercropping.