Abstract
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.
Highlights
The plant rhizomicrobiome, comprising different microbial communities, plays immense roles in many processes of ecosystem functioning, such as nutrient recycling, suppressing disease pathogens, secreting plant growth-promoting enzymes, and mineralization of organic matter, which lead to increased soil fertility and crop productivity [1,2]
This study revealed the differences in microbial functional genes, those involved in nutrient mobilization, plant growth promotion, and carbon cycling of land previously used as pasture, and of land that had been under intensive cultivation for several years
Shotgun metagenomic sequencing was applied on maize rhizosphere soils to elucidate the effects of land-use and management histories on the diversity and composition of microbial functional genes involved in plant growth promotion and carbon cycling
Summary
The plant rhizomicrobiome, comprising different microbial communities, plays immense roles in many processes of ecosystem functioning, such as nutrient recycling, suppressing disease pathogens, secreting plant growth-promoting enzymes, and mineralization of organic matter, which lead to increased soil fertility and crop productivity [1,2]. Soil ecosystem functioning is mostly determined by the activity and complexity of the inhabiting microbes These microbes are influenced by several biological, chemical, and physical properties of the soil environment [1,7]. The microbial community composition in soils can be altered by different land-use and management practices, which affect certain ecosystem functioning in soils [8,9]. Most studies on the effects of land-use practices on the soil ecosystem functions focused mainly on the composition and structure of soil microbial communities [12,13]. Quantifying the knowledge of the functional capabilities of microbial communities in soils will help identify their roles in the ecosystems, how they are impacted by land-use and management practices, and their influence on soil ecosystem functions. Quantifying the knowledge of the functional capabilities of microbial communities in soils will help identify their roles in the ecosystems, how they are impacted by land-use and management practices, and their influence on soil ecosystem functions. such as organic matter mineralization, nutrient cycling, degradation of organic pollutants, and plant–microbe interactions [9,18,19]
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