Phylogenetic relationships among introduced and autochthonous rhizobia nodulating Trifolium spp. in Uruguayan soils

Tartaglia, Carolina; Azziz, Gastón; Lorite, María J.; Sanjuán, Juan; Monza, Jorge

doi:10.1016/j.apsoil.2019.03.014

Cited by 6 publications

(17 citation statements)

References 26 publications

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“…In field conditions, natural transfer of symbiotic islands has in fact been shown in mesorhizobia, where resident non-nodulating bacteria accepted symbiotic genes from the inoculant strain and formed new nodulating species (Nandasena et al, 2007; Sotelo et al, 2011). Some of the native strains of rhizobia used in the present study share the same symbiotic genes with U204 but in different chromosomal backgrounds (Tartaglia et al, 2019).…”

Section: Discussionmentioning

confidence: 99%

Selection of Competitive and Efficient Rhizobia Strains for White Clover

et al. 2019

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The practice of inoculating forage legumes with rhizobia strains is widespread. It is assumed that the inoculated strain determines the performance of the symbiosis and nitrogen fixation rates. However, native-naturalized strains can be competitive, and actual nodule occupancy is often scarcely investigated. In consequence, failures in establishment, and low productivity attributed to poor performance of the inoculant may merely reflect the absence of the inoculated strain in the nodules. This study lays out a strategy followed for selecting a Rhizobium leguminosarum sv. trifolii strain for white clover ( Trifolium repens ) with competitive nodule occupancy. First, the competitiveness of native-naturalized rhizobia strains selected for their efficiency to fix N 2 in clover and tagged with gus A was evaluated in controlled conditions with different soils. Second, three of these experimental strains with superior nodule occupancy plus the currently recommended commercial inoculant, an introduced strain, were tested in the field in 2 years and at two sites. Plant establishment, herbage productivity, fixation of atmospheric N 2 ( 15 N natural abundance), and nodule occupancy (ERIC-PCR genomic fingerprinting) were measured. In both years and sites, nodule occupancy of the native-naturalized experimental strains was either higher or similar to that of the commercial inoculant in both primary and secondary roots. The difference was even greater in stolon roots nodules, where nodule occupancy of the native-naturalized experimental strains was at least five times greater. The amount of N fixed per unit plant mass was consistently higher with native-naturalized experimental strains, although the proportion of N derived from atmospheric fixation was similar for all strains. Plant establishment and herbage production, as well as clover contribution in oversown native grasslands, were either similar or higher in white clover inoculated with the native-naturalized experimental strains. These results support the use of our implemented strategy for developing a competitive inoculant from native-naturalized strains.

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Section: Discussionmentioning

confidence: 99%

Selection of Competitive and Efficient Rhizobia Strains for White Clover

et al. 2019

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“…To ensure good development there is a recommendation, since 1967, of inoculation of both clovers with R. leguminosarum sv. trifolii strain U204, a commercial inoculant strain introduced from the USA (Tartaglia et al 2019).…”

Section: Main Inoculated Cropsmentioning

confidence: 99%

Microbial inoculants: reviewing the past, discussing the present and previewing an outstanding future for the use of beneficial bacteria in agriculture

2019

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More than one hundred years have passed since the development of the first microbial inoculant for plants. Nowadays, the use of microbial inoculants in agriculture is spread worldwide for different crops and carrying different microorganisms. In the last decades, impressive progress has been achieved in the production, commercialization and use of inoculants. Nowadays, farmers are more receptive to the use of inoculants mainly because high-quality products and multi-purpose elite strains are available at the market, improving yields at low cost in comparison to chemical fertilizers. In the context of a more sustainable agriculture, microbial inoculants also help to mitigate environmental impacts caused by agrochemicals. Challenges rely on the production of microbial inoculants for a broader range of crops, and the expansion of the inoculated area worldwide, in addition to the search for innovative microbial solutions in areas subjected to increasing episodes of environmental stresses. In this review, we explore the world market for inoculants, showing which bacteria are prominent as inoculants in different countries, and we discuss the main research strategies that might contribute to improve the use of microbial inoculants in agriculture.

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“…In soils in which clovers are sown, there are populations of native-naturalized clover rhizobia, which include strains with similar symbiotic efficiency to the commercial inoculant U204, other strains with lower efficiency [2,3], and even so-called parasitic rhizobia that are ineffective [4][5][6]. Moreover, analysis of 16S rRNA and ITS sequences, as well as housekeeping (atpD, glnII, recA, rpoB) and symbiotic genes (nodA, nodC, nifH), allowed us to determine the identities and phylogenetic relationships among these rhizobia [7]. The native parasitic clover rhizobia are phylogenetically distinct from the efficient rhizobia, either native to Uruguay or introduced in the country [7].…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, analysis of 16S rRNA and ITS sequences, as well as housekeeping (atpD, glnII, recA, rpoB) and symbiotic genes (nodA, nodC, nifH), allowed us to determine the identities and phylogenetic relationships among these rhizobia [7]. The native parasitic clover rhizobia are phylogenetically distinct from the efficient rhizobia, either native to Uruguay or introduced in the country [7].…”

Section: Introductionmentioning

confidence: 99%

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Competitiveness and Phylogenetic Relationship of Rhizobial Strains with Different Symbiotic Efficiency in Trifolium repens: Conversion of Parasitic into Non-Parasitic Rhizobia by Natural Symbiotic Gene Transfer

Morel

Berais-Rubio

Giménez

et al. 2023

Biology

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In Uruguayan soils, populations of native and naturalized rhizobia nodulate white clover. These populations include efficient rhizobia but also parasitic strains, which compete for nodule occupancy and hinder optimal nitrogen fixation by the grassland. Nodulation competitiveness assays using gusA-tagged strains proved a high nodule occupancy by the inoculant strain U204, but this was lower than the strains with intermediate efficiencies, U268 and U1116. Clover biomass production only decreased when the parasitic strain UP3 was in a 99:1 ratio with U204, but not when UP3 was at equal or lower numbers than U204. Based on phylogenetic analyses, strains with different efficiencies did not cluster together, and U1116 grouped with the parasitic strains. Our results suggest symbiotic gene transfer from an effective strain to U1116, thereby improving its symbiotic efficiency. Genome sequencing of U268 and U204 strains allowed us to assign them to species Rhizobium redzepovicii, the first report of this species nodulating clover, and Rhizobium leguminosarun, respectively. We also report the presence of hrrP- and sapA-like genes in the genomes of WSM597, U204, and U268 strains, which are related to symbiotic efficiency in rhizobia. Interestingly, we report here chromosomally located hrrP-like genes.

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Phylogenetic relationships among introduced and autochthonous rhizobia nodulating Trifolium spp. in Uruguayan soils

Cited by 6 publications

References 26 publications

Selection of Competitive and Efficient Rhizobia Strains for White Clover

Selection of Competitive and Efficient Rhizobia Strains for White Clover

Microbial inoculants: reviewing the past, discussing the present and previewing an outstanding future for the use of beneficial bacteria in agriculture

Competitiveness and Phylogenetic Relationship of Rhizobial Strains with Different Symbiotic Efficiency in Trifolium repens: Conversion of Parasitic into Non-Parasitic Rhizobia by Natural Symbiotic Gene Transfer

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