Abstract
Long-term continuous monocropping negatively influences the physicochemical and biological characteristics of cultivated soil, especially for the economically important crop of flue-cured tobacco that is intolerant to continuous monocropping. The underlying mechanism of soil sickness under continuous monoculture and the temporal dynamic changes over the tobacco life cycle among different monoculture time spans remain poorly characterized. In this study, high-throughput sequencing targeting the 16S rRNA gene phylogenetic marker was performed on 60 soil samples of rhizosphere soil from flue−cured tobacco in the replanting, growth and harvest period across 5, 10, and 20 years of a continuous monocropping system. Bacterial community diversity decreased with the increase in duration of continuous monocropping, and the rhizosphere microbiota was highly dynamic in the harvest period. The random forests algorithm identified 17 taxa as biomarkers and a model was established to correlate root microbiota with continuous monocropping time of flue-cured tobacco. Molecular ecological network analysis elaborated the differences and interactions in bacterial co-occurrence patterns under different monocropping systems. The co-occurrence microbial network was larger in size but there were fewer interactions among microbial communities with the increase in continuous monocropping duration. These results provide insights into the changes of flue−cured tobacco root microbiome diversity in response to continuous monocropping and suggest a model for successional dynamics of the root-associated microbiota over continuous monocropping time and development stage. This study may help elucidate the theoretical basis underlying obstacles to continuous monocropping and could contribute to improving guidance for tobacco production.
Highlights
Rhizospheres recruit and assemble soil-derived microbial communities, forming a unique microecosystem that is mutually beneficial to plant roots and root-associated microbiota (Edwards et al, 2015, 2018)
Continuous monocropping causing dynamic disturbance and transformation of soil microorganisms has been reported in previous studies on various crops (Dang et al, 2020; Lei et al, 2020)
The current study observed that rhizosphere bacterial diversity of flue-cured tobacco was highly correlated with the time span of continuous monoculture
Summary
Rhizospheres recruit and assemble soil-derived microbial communities, forming a unique microecosystem that is mutually beneficial to plant roots and root-associated microbiota (Edwards et al, 2015, 2018). Beneficial microbiota in the rhizosphere convert critical soil nutrients to more usable forms for root assimilation, as well as contributing to pathogen resistance (Edwards et al, 2015; Gao et al, 2019). The rhizosphere is the primary area for signal communication, and material and energy exchanges among plants, soil, and microorganisms (Levy et al, 2018; Rodriguez et al, 2019). There is limited information available about how spatiotemporal dynamics of rhizosphere microbiota vary on monthly timescales from seedling to maturity stage of a plant life cycle, and what patterns of change can be expected over years of continuous monocropping for annual plants
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