NifH Gene Sequencing Reveals the Effects of Successive Monoculture on the Soil Diazotrophic Microbial Community in Casuarina equisetifolia Plantations.

Liuting Zhou,Jun Chen,Ganga Raj Pokhrel,Jianjuan Li,Ying Bai,Chen Zhang,Zeyan Wu,Wenxiong Lin,Chengzhen Wu,Yanlin Zhao

doi:10.3389/fpls.2020.578812

Liuting Zhou, Jun Chen + Show 8 more

Open Access

https://doi.org/10.3389/fpls.2020.578812

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Abstract

The growth and productivity of Casuarina equisetifolia is negatively impacted by planting sickness under long-term monoculture regimes. In this study, Illumina MiSeq sequencing targeting nifH genes was used to assess variations in the rhizospheric soil diazotrophic community under long-term monoculture rotations. Principal component analysis and unweighted pair-group method with arithmetic means (UPGMA) clustering demonstrated distinct differences in diazotrophic community structure between uncultivated soil (CK), the first rotation plantation (FCP), the second rotation plantation (SCP), and the third rotation plantation (TCP). Taxonomic analysis showed that the phyla Proteobacteria increased while Verrucomicrobia decreased under the consecutive monoculture (SCP and TCP). The relative abundance of Paraburkholderia, Rhodopseudomonas, Bradyrhizobium, Geobacter, Pseudodesulfovibrio, and Frankia increased significantly while Burkholderia, Rubrivivax, and Chlorobaculum declined significantly at the genus level under consecutive monoculture (SCP and TCP). Redundancy analysis (RDA) showed that Burkholderia, Rubrivivax, and Chlorobaculum were positively correlated with total nitrogen and available nitrogen. In conclusion, continuous C. equisetifolia monoculture could change the structure of diazotrophic microbes in the rhizosphere, resulting in the imbalance of the diazotrophic bacteria population, which might be a crucial factor related to replanting disease in this cultivated tree species.

Highlights

Casuarina equisetifolia Forst has covers over 300,000 ha in southeastern China
The results of soil nutrient analysis showed that replanting soils had a lower level of pH under the extended C. equisetifolia monoculture regime
The results indicated that soil physical and chemical properties may indirectly affect the healthy growth of C. equisetifolia through regulating the structure of the soil microbial community (Berendsen et al, 2012)

Summary

Introduction

Casuarina equisetifolia Forst has covers over 300,000 ha in southeastern China It is one of the preferred trees for forming shelterbelts in coastal areas, as it vegetates the coasts and contributes to stabilizing coastal sand and protecting against storms (Zhong et al, 2005; Karthikeyan et al, 2013). Continuous monocultures of C. equisetifolia result in productivity decline and regeneration failure. This phenomenon is referred to as the consecutive monoculture problem (CMP) (Wardle et al, 2004). The depletion in soil nutrients (Bennett et al, 2012), the autointoxication of root exudations (Araya et al, 2012), and the imbalance of rhizospheric microflora (Wu et al, 2016a) are thought to be the main reasons for CMP. Similar results were found in Chinese fir, Eucalyptus, and Pinus halepensis (Fernandez et al, 2008; Jie et al, 2014; Wu et al, 2017)

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