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Agyekum DVA, Kobayashi T, Dastogeer KMG, Yasuda M, Sarkodee-Addo E, Ratu STN, Xu Q, Miki T, Matsuura E, Okazaki S. Diversity and function of soybean rhizosphere microbiome under nature farming. Front Microbiol 2023; 14:1130969. [PMID: 36937301 PMCID: PMC10014912 DOI: 10.3389/fmicb.2023.1130969] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2022] [Accepted: 02/10/2023] [Indexed: 03/05/2023] Open
Abstract
Nature farming is a farming system that entails cultivating crops without using chemical fertilizers and pesticides. The present study investigated the bacterial and fungal communities in the rhizosphere of soybean grown in conventional and nature farming soils using wild-type and non-nodulating mutant soybean. The effect of soil fumigant was also analyzed to reveal its perturbation of microbial communities and subsequent effects on the growth of soybean. Overall, the wild-type soybean exhibited a better growth index compared to mutant soybean and especially in nature farming. Nodulation and arbuscular mycorrhiza (AM) fungi colonization were higher in plants under nature farming than in conventionally managed soil; however, fumigation drastically affected these symbioses with greater impacts on plants in nature farming soil. The rhizosphere microbiome diversity in nature farming was higher than that in conventional farming for both cultivars. However, the diversity was significantly decreased after fumigation treatment with a greater impact on nature farming. Principal coordinate analysis revealed that nature farming and conventional farming soil harbored distinct microbial communities and that soil fumigation significantly altered the communities in nature farming soils but not in conventional farming soils. Intriguingly, some beneficial microbial taxa related to plant growth and health, including Rhizobium, Streptomyces, and Burkholderia, were found as distinct microbes in the nature farming soil but were selectively bleached by fumigant treatment. Network analysis revealed a highly complex microbial network with high taxa connectivity observed under nature farming soil than in conventional soil; however, fumigation strongly broke it. Overall, the results highlighted that nature farming embraced higher microbial diversity and the abundance of beneficial soil microbes with a complex and interconnected network structure, and also demonstrated the underlying resilience of the microbial community to environmental perturbations, which is critical under nature farming where chemical fertilizers and pesticides are not applied.
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Affiliation(s)
- Dominic V. A. Agyekum
- United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Fuchu, Japan
| | - Tatsuyuki Kobayashi
- Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Japan
| | - Khondoker M. G. Dastogeer
- Department of Plant Pathology, Faculty of Agriculture, Bangladesh Agricultural University, Mymensingh, Bangladesh
| | - Michiko Yasuda
- Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Japan
| | - Elsie Sarkodee-Addo
- Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Japan
| | - Safirah T. N. Ratu
- Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, Fuchu, Japan
| | - Qicong Xu
- International Nature Farming Research Center, Nagano, Japan
| | - Takaaki Miki
- International Nature Farming Research Center, Nagano, Japan
| | - Eri Matsuura
- College of Agriculture, Ibaraki University, Mito, Japan
| | - Shin Okazaki
- United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Fuchu, Japan
- Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Japan
- Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, Fuchu, Japan
- *Correspondence: Shin Okazaki,
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Nguyen HP, Ratu STN, Yasuda M, Göttfert M, Okazaki S. InnB, a Novel Type III Effector of Bradyrhizobium elkanii USDA61, Controls Symbiosis With Vigna Species. Front Microbiol 2018; 9:3155. [PMID: 30619219 PMCID: PMC6305347 DOI: 10.3389/fmicb.2018.03155] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2018] [Accepted: 12/05/2018] [Indexed: 12/14/2022] Open
Abstract
Bradyrhizobium elkanii USDA61 is incompatible with mung bean (Vigna radiata cv. KPS1) and soybean (Glycine max cv. BARC2) and unable to nodulate either plant. This incompatibility is due to the presence of a functional type III secretion system (T3SS) that translocates effector protein into host cells. We previously identified five genes in B. elkanii that are responsible for its incompatibility with KPS1 plants. Among them, a novel gene designated as innB exhibited some characteristics associated with the T3SS and was found to be responsible for the restriction of nodulation on KPS1. In the present study, we further characterized innB by analysis of gene expression, protein secretion, and symbiotic phenotypes. The innB gene was found to encode a hypothetical protein that is highly conserved among T3SS-harboring rhizobia. Similar to other rhizobial T3SS-associated genes, the expression of innB was dependent on plant flavonoids and a transcriptional regulator TtsI. The InnB protein was secreted via the T3SS and was not essential for secretion of other nodulation outer proteins. In addition, T3SS-dependent translocation of InnB into nodule cells was confirmed by an adenylate cyclase assay. According to inoculation tests using several Vigna species, InnB promoted nodulation of at least one V. mungo cultivar. These results indicate that innB encodes a novel type III effector controlling symbiosis with Vigna species.
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Affiliation(s)
- Hien P Nguyen
- United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Tokyo, Japan
| | - Safirah T N Ratu
- Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, Japan
| | - Michiko Yasuda
- Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, Japan
| | - Michael Göttfert
- Institute of Genetics, Technische Universität Dresden, Dresden, Germany
| | - Shin Okazaki
- United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Tokyo, Japan.,Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, Japan
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