Nitrogen fixation capacity and nodule occupancy by Bradyrhizobium japonicum and B. elkanii strains

Hungría, Mariangela; Boddey, L. H.; Santos, Maria Aparecida dos; Vargas, M. A. T.

doi:10.1007/s003740050449

Cited by 64 publications

(59 citation statements)

References 26 publications

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“…SEMIA 566 is the putative parental strain of SEMIA 5079 (Hungria and Vargas 2000;Hungria et al 2006), yet the strains show differences in several morphological, physiological, symbiotic and genetic properties, including DNA profiles with specific or random primers (Boddey and Hungria 1997;Hungria et al 1996Hungria et al , 1998Hungria et al , 2006Nishi et al 1996;Santos et al 1999;Ferreira et al 2000;Ferreira and Hungria 2002). Together, those two very competitive strains, which belong to the same serogroup as USDA 123 (Mendes et al 2004;Hungria et al 2006), represented 18% of all the nodules sampled (Table 3).…”

Section: Resultsmentioning

confidence: 99%

“…However, dispersal of inoculant strains did occur (Ferreira and Hungria 2002;Mendes et al 2004) and Andrade and Hungria (2002) demonstrated that viable cells on the soybean seed coat can be transported to new cropping areas. After introduction through inoculation and some years of adaptation to the soil conditions, a high level of diversity in morphological, physiological, genetic, and symbiotic properties has been reported especially under the stressful conditions of the Cerrados (Hungria et al , 1998Nishi et al 1996;Boddey and Hungria 1997;Santos et al 1999;Hungria and Vargas 2000;Galli-Terasawa et al 2003;Batista et al 2006). In the USA, Streeter (1994) has also noted substantial "genetic adjustment" during the period of adaptation, leading to wide genetic diversity in field populations.…”

Section: Resultsmentioning

confidence: 99%

“…First, the harsh environmental conditions seem to favor genetic processes that lead to high variability (Hungria et al 1998;Santos et al 1999;Hungria and Vargas 2000;Galli-Terasawa et al 2003;Batista et al 2006). Second, diversity would be increased with genetic exchanges between exotic Bradyrhizobium strains and indigenous strains that nodulate native legumes.…”

Section: Resultsmentioning

confidence: 99%

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Soybean [Glycine max (L.) Merrill] rhizobial diversity in Brazilian oxisols under various soil, cropping, and inoculation managements

et al. 2006

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In this study, soybean nodules were collected from 12 sites in the State of Mato Grosso, in the Brazilian Cerrados, where both exotic soybean [Glycine max (L.) Merrill] and bradyrhizobial strains have been introduced from 1 to 18 years before. All soils were originally devoid of rhizobia capable of effectively nodulating soybean and varied in terms of chemical and physical properties, inoculation procedures, and cropping systems. Rhizobial genetic diversity was assessed on 240 isolates by rep-PCR fingerprinting with BOX primer, and indices of diversity (abundance-based coverage estimator and traditional and modified Shannon indices) were applied to the profiles obtained. The genetic diversity was much greater than expected, as after the introduction of a maximum of four strains, up to 13 profiles were identified, some sharing many similar bands with the inoculant strains, but others quite distinct from the putative parental genotypes. The increase in the number of rep-PCR profiles could be attributed to genetic variability due to the stressful tropical environmental conditions, but also might indicate that indigenous rhizobia become capable of nodulating the host legume. After the third year of cropping with the host legume, inoculation did not affect rhizobial diversity. A high content of clay decreased diversity in comparison with that seen in a sandy soil, probably due to reduced aeration. Diversity was higher under the no-tillage system when compared to the conventional tillage management, highlighting the importance of maintaining crop residues in tropical soils. Understanding the ecology of exotic rhizobia after being introduced into new cropping areas represents a first step towards the establishment of better strategies of inoculation, which in turn may result in sustainability and higher plant yields.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Soybean [Glycine max (L.) Merrill] rhizobial diversity in Brazilian oxisols under various soil, cropping, and inoculation managements

et al. 2006

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“…In comparison to the putative parental genotypes, variant strains were different in several morphological, physiological, genetic, and symbiotic properties (3,22,44). We selected seven variant strains of SEMIA 566 and six of SEMIA 586.…”

Section: Methodsmentioning

confidence: 99%

“…In these areas, exotic strains of B. japonicum and B. elkanii were introduced a decade ago. Compared to the putative parental strains, several of these isolates have shown differences in morphological, serological, physiological, genetic, and symbiotic properties (3,19,22,33,38,44). Variability might be caused by the stressful environmental conditions of the Cerrados, where long periods of high temperature and drought often prevail (18).…”

mentioning

confidence: 99%

Evidence of Horizontal Transfer of Symbiotic Genes from a Bradyrhizobium japonicum Inoculant Strain to Indigenous Diazotrophs Sinorhizobium ( Ensifer ) fredii and Bradyrhizobium elkanii in a Brazilian Savannah Soil

Barcellos

Menna

Batista

et al. 2007

Appl Environ Microbiol

181

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The importance of horizontal gene transfer (HGT) in the evolution and speciation of bacteria has been emphasized; however, most studies have focused on genes clustered in pathogenesis and very few on symbiosis islands. Both soybean (Glycine max [L.] Merrill) and compatible Bradyrhizobium japonicum and Bradyrhizobium elkanii strains are exotic to Brazil and have been massively introduced in the country since the early 1960s, occupying today about 45% of the cropped land. For the past 10 years, our group has obtained several isolates showing high diversity in morphological, physiological, genetic, and symbiotic properties in relation to the putative parental inoculant strains. In this study, parental strains and putative natural variants isolated from field-grown soybean nodules were genetically characterized in relation to conserved genes (by repetitive extragenic palindromic PCR using REP and BOX A1R primers, PCR-restriction fragment length polymorphism, and sequencing of the 16SrRNA genes), nodulation, and N2-fixation genes (PCR-RFLP and sequencing of nodY-nodA, nodC, and nifH genes). Both genetic variability due to adaptation to the stressful environmental conditions of the Brazilian Cerrados and HGT events were confirmed. One strain (S 127) was identified as an indigenous B. elkanii strain that acquired a nodC gene from the inoculant B. japonicum. Another one (CPAC 402) was identified as an indigenous Sinorhizobium (Ensifer) fredii strain that received the whole symbiotic island from the B. japonicum inoculant strain and maintained an extra copy of the original nifH gene. The results highlight the strategies that bacteria may commonly use to obtain ecological advantages, such as the acquisition of genes to establish effective symbioses with an exotic host legume.

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Improvement of rhizobium‐soybean symbiosis and nitrogen fixation under drought

Kibido

Kunert

Makgopa

et al. 2019

Food and Energy Security

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The symbiotic interaction between soybean plants and rhizobacteria can be severely affected by drought, which results in a reduction in symbiotic nitrogen fixation and ultimately decreased yields. The aim of our research was to determine whether symbiotically efficient rhizobia that can better tolerate soil water deficits can improve nodule performance in plants subjected to drought. Firstly, rhizobial strains were selected that exhibited differences in tolerance to salt (NaCl) or water deficit (PEG 6000). Sinorhizobium fredii strain SMH12 showed the highest tolerance to these treatments while Bradyrhizobium diazoefficiens strain WB74‐1 showed the lowest tolerance. Greenhouse‐grown Prima 2000 soybean plants were then inoculated with either SMH12 or WB74‐1 and subjected to two water deficit regimes. Different nodule and plant growth traits were determined, including nodule number, dry weight, water potential, and the accumulation of malondialdehyde and ureide. Plants inoculated with SMH12 had significantly more nodules under water deficit conditions than those inoculated WB74‐1, despite having lower root and shoot biomass. SMH12‐inoculated plants had higher nodule water potentials and lower malondialdehyde contents than the WB74‐1‐inoculated plants. These results demonstrate that inoculation of soybean plants with the more water deficit‐tolerant S. fredii strain improved nodule characteristics when plants were grown under water deficit conditions. However, these improved nodule characteristics do not always directly translate into better plant growth.

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Nitrogen fixation capacity and nodule occupancy by Bradyrhizobium japonicum and B. elkanii strains

Cited by 64 publications

References 26 publications

Soybean [Glycine max (L.) Merrill] rhizobial diversity in Brazilian oxisols under various soil, cropping, and inoculation managements

Soybean [Glycine max (L.) Merrill] rhizobial diversity in Brazilian oxisols under various soil, cropping, and inoculation managements

Evidence of Horizontal Transfer of Symbiotic Genes from a Bradyrhizobium japonicum Inoculant Strain to Indigenous Diazotrophs Sinorhizobium ( Ensifer ) fredii and Bradyrhizobium elkanii in a Brazilian Savannah Soil

Improvement of rhizobium‐soybean symbiosis and nitrogen fixation under drought

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