Many studies have shown that the maize rhizosphere comprises several plant growth-promoting microbes, but there is little or no study on the effects of land-use and management histories on microbial functional gene diversity in the maize rhizosphere soils in Africa. Analyzing microbial genes in the rhizosphere of plants, especially those associated with plant growth promotion and carbon cycling, is important for improving soil fertility and crop productivity. Here, we provide a comparative analysis of microbial genes present in the rhizosphere samples of two maize fields with different agricultural histories using shotgun metagenomics. Genes involved in the nutrient mobilization, including nifA, fixJ, norB, pstA, kefA and B, and ktrB were significantly more abundant (α = 0.05) in former grassland (F1) rhizosphere soils. Among the carbon-cycling genes, the abundance of 12 genes, including all those involved in the degradation of methane were more significant (α = 0.05) in the F1 soils, whereas only five genes were significantly more abundant in the F2 soils. α-diversity indices were different across the samples and significant differences were observed in the β diversity of plant growth-promoting and carbon-cycling genes between the fields (ANOSIM, p = 0.01 and R = 0.52). Nitrate-nitrogen (N-NO₃) was the most influential physicochemical parameter (p = 0.05 and contribution = 31.3%) that affected the distribution of the functional genes across the samples. The results indicate that land-use and management histories impact the composition and diversity of plant growth-promoting and carbon-cycling genes in the plant rhizosphere. The study widens our understanding of the effects of anthropogenic activities on plant health and major biogeochemical processes in soils.

中文翻译：

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具有不同土地利用和管理历史的玉米根际土壤中植物生长促进和碳循环基因的宏基因组分析

许多研究表明，玉米根际包含几种促进植物生长的微生物，但很少或没有关于土地利用和管理历史对非洲玉米根际土壤微生物功能基因多样性影响的研究。分析植物根际微生物基因，尤其是与植物生长促进和碳循环相关的微生物基因，对于提高土壤肥力和作物生产力具有重要意义。在这里，我们使用鸟枪法宏基因组学对两个具有不同农业历史的玉米田的根际样本中存在的微生物基因进行了比较分析。参与养分动员的基因，包括nif A、fix J、nor B、pst A、kefA 和 B，以及ktr B 在前草地 (F1) 根际土壤中明显更丰富 (α = 0.05)。在碳循环基因中，包括所有参与甲烷降解的基因在内的 12 个基因在 F1 土壤中的丰度更为显着（α = 0.05），而在 F2 土壤中只有 5 个基因的丰度显着更高。不同样品的α多样性指数不同，不同田间植物促生基因和碳循环基因的β多样性存在显着差异（ANOSIM，p = 0.01，R = 0.52）。硝酸盐-氮 (N-NO ₃ ) 是最有影响力的理化参数 ( p =0.05 和贡献 = 31.3%）影响了样本中功能基因的分布。结果表明，土地利用和管理历史影响植物根际促进植物生长和碳循环基因的组成和多样性。该研究拓宽了我们对人为活动对植物健康和土壤中主要生物地球化学过程的影响的理解。