Maximizing Nitrogen Fixation in Legumes as a Tool for Sustainable Agriculture Intensification

Editorial

23 November 2021

Editorial: Maximizing Nitrogen Fixation in Legumes as a Tool for Sustainable Agriculture Intensification

Pilar Irisarri

Juan Imperial

Fernando A. Lattanzi

Jorge Monza

, 2 more and

Julie Grossman

4,163 views

12 citations

Editors

Pilar Irisarri

Universidad de la República

Juan Imperial

Spanish National Research Council (CSIC)

Fernando Alfredo Lattanzi

National Institute for Agricultural Research (INIA)

Jorge Monza

Universidad de la República

Jose Palacios

Polytechnic University of Madrid

JUAN SANJUAN

Experimental Station of Zaidín, Spanish National Research Council (CSIC)

Julie Grossman

University of Minnesota Twin Cities

Impact

Original Research

07 September 2021

Genomic Diversity of Pigeon Pea (Cajanus cajan L. Millsp.) Endosymbionts in India and Selection of Potential Strains for Use as Agricultural Inoculants

Beatriz Jorrin

, 16 more and

Philip S. Poole

Pigeon pea (Cajanus cajan L. Millsp. ) is a legume crop resilient to climate change due to its tolerance to drought. It is grown by millions of resource-poor farmers in semiarid and tropical subregions of Asia and Africa and is a major contributor to their nutritional food security. Pigeon pea is the sixth most important legume in the world, with India contributing more than 70% of the total production and harbouring a wide variety of cultivars. Nevertheless, the low yield of pigeon pea grown under dry land conditions and its yield instability need to be improved. This may be done by enhancing crop nodulation and, hence, biological nitrogen fixation (BNF) by supplying effective symbiotic rhizobia through the application of “elite” inoculants. Therefore, the main aim in this study was the isolation and genomic analysis of effective rhizobial strains potentially adapted to drought conditions. Accordingly, pigeon pea endosymbionts were isolated from different soil types in Southern, Central, and Northern India. After functional characterisation of the isolated strains in terms of their ability to nodulate and promote the growth of pigeon pea, 19 were selected for full genome sequencing, along with eight commercial inoculant strains obtained from the ICRISAT culture collection. The phylogenomic analysis [Average nucleotide identity MUMmer (ANIm)] revealed that the pigeon pea endosymbionts were members of the genera Bradyrhizobium and Ensifer. Based on nodC phylogeny and nod cluster synteny, Bradyrhizobium yuanmingense was revealed as the most common endosymbiont, harbouring nod genes similar to those of Bradyrhizobium cajani and Bradyrhizobium zhanjiangense. This symbiont type (e.g., strain BRP05 from Madhya Pradesh) also outperformed all other strains tested on pigeon pea, with the notable exception of an Ensifer alkalisoli strain from North India (NBAIM29). The results provide the basis for the development of pigeon pea inoculants to increase the yield of this legume through the use of effective nitrogen-fixing rhizobia, tailored for the different agroclimatic regions of India.

21,262 views

21 citations

Nodulation (A,B), plant biomass (C), and grain yield (D) of common bean variety PAN128 sampled from the fields of 14 farmers in Eastern Cape Province, in the 2014 cropping season. NPK (2:3:2), limestone ammonium nitrate (LAN, 28% N), and urea were each used at rates of 100 kg ha−1. For each location on the x-axis, the numbers 1, 2, 3, … represent different fields within that location. Bars with dissimilar letters are significantly different at p ≤ 0.05.

Original Research

08 September 2021

Inhibition of N2 Fixation by N Fertilization of Common Bean (Phaseolus vulgaris L.) Plants Grown on Fields of Farmers in the Eastern Cape of South Africa, Measured Using 15N Natural Abundance and Tissue Ureide Analysis

Simon J. Habinshuti

, 1 more and

Felix D. Dakora

2,467 views

5 citations

Suggested steps for developing elite rhizobial inoculants from native strains. (A) Perform physical, chemical, and microbiological soil analysis. Although we recognize the importance of full microbiome interactions with the plant, this review will focus on rhizobial inoculants. (B) Trapping assays using the desired host genotype and soil of interest, followed by the identification and characterisation of native rhizobia [i.e., Most probable number (MPN) – and strain-specific fingerprints], and preparation of rhizobial isolate libraries. (C) Multi-strain inoculations in the plant genotype using the same soil from which strains where isolated. Perform simultaneous assessment of rhizobial competitiveness and N2-effectiveness, followed by the identification of elite strains by next-generation sequencing (NGS). Analysis of multicomponent interaction studies using a multidisciplinary approach and final scaling-up and formulation based on the elite strains with best performance in the soil under study for a tailored inoculant.

Review

19 August 2021

Competition, Nodule Occupancy, and Persistence of Inoculant Strains: Key Factors in the Rhizobium-Legume Symbioses

Marcela Mendoza-Suárez

, 2 more and

Carmen Sánchez-Cañizares

Biological nitrogen fixation by Rhizobium-legume symbioses represents an environmentally friendly and inexpensive alternative to the use of chemical nitrogen fertilizers in legume crops. Rhizobial inoculants, applied frequently as biofertilizers, play an important role in sustainable agriculture. However, inoculants often fail to compete for nodule occupancy against native rhizobia with inferior nitrogen-fixing abilities, resulting in low yields. Strains with excellent performance under controlled conditions are typically selected as inoculants, but the rates of nodule occupancy compared to native strains are rarely investigated. Lack of persistence in the field after agricultural cycles, usually due to the transfer of symbiotic genes from the inoculant strain to naturalized populations, also limits the suitability of commercial inoculants. When rhizobial inoculants are based on native strains with a high nitrogen fixation ability, they often have superior performance in the field due to their genetic adaptations to the local environment. Therefore, knowledge from laboratory studies assessing competition and understanding how diverse strains of rhizobia behave, together with assays done under field conditions, may allow us to exploit the effectiveness of native populations selected as elite strains and to breed specific host cultivar-rhizobial strain combinations. Here, we review current knowledge at the molecular level on competition for nodulation and the advances in molecular tools for assessing competitiveness. We then describe ongoing approaches for inoculant development based on native strains and emphasize future perspectives and applications using a multidisciplinary approach to ensure optimal performance of both symbiotic partners.

21,914 views

75 citations

(A) Nucleotide sequence of wild-type alleles of MsNOD26 gene (MSAD_247675) from clone C23. In this picture, we highlighted the first two exons (exon1 and exon2), the two guides (sgRNA1 and sgRNA2) and the sequence recognized by the Cas9 nuclease (PAM sequences) and the primers (MsNOD26-up and MsNOD26-low) used for the identification of edited events using high-resolution fragment assays. (B) Flow cytometry fluorescence intensities of wild-type (499-bp) and mutant (492–498 bp) alleles of MsNOD26 gene. This figure shows representative examples of different genotypes. (C) Sequence analysis showed small deletions (1, 2, and 6-bp) within the alleles of MsNOD26 gene in CRISPR/Cas9-editing event 36.

Brief Research Report

16 July 2021

Efficient CRISPR/Cas9 Genome Editing in Alfalfa Using a Public Germplasm

Emilia Bottero

, 9 more and

Gabriela Soto

4,109 views

17 citations

Mini Review

05 July 2021

Rhizobial Exopolysaccharides and Type VI Secretion Systems: A Promising Way to Improve Nitrogen Acquisition by Legumes

Bruna Fernanda Silva De Sousa

, 3 more and

Luis Rey

4,001 views

7 citations

Brief Research Report

29 June 2021

Introduction of H2-Uptake Hydrogenase Genes Into Rhizobial Strains Improves Symbiotic Nitrogen Fixation in Vicia sativa and Lotus corniculatus Forage Legumes

Mariana Sotelo

, 4 more and

Jose Palacios

3,775 views

3 citations

Original Research

13 August 2021

Black Seedcoat Pigmentation Is a Marker for Enhanced Nodulation and N2 Fixation in Bambara Groundnut (Vigna Subterranea L. Verdc.) Landraces

Doris K. Puozaa

, 1 more and

Felix D. Dakora

1,392 views

8 citations

Original Research

21 July 2021

Analysis of Nitrogenase Fe Protein Activity in Transplastomic Tobacco

Jose A. Aznar-Moreno

, 2 more and

Luis M. Rubio

2,103 views

4 citations

Model of a M. truncatula nodule illustrating the patterns of expression of NCR genes. The different stages of nodule development are named on the left. The intensity of color in the cells of these zones in the nodule reflects the relative expression of all the NCRs based on the data from Roux et al. (2014). NCRs were grouped into clusters by Roux et al. (2014) based on their expression patterns and the relative levels of expression of NCRs in the six clusters representing most of the NCRs are shown on the right panel. The color intensity illustrates their average patterns of expression in the different developmental stages with which they are aligned.

Mini Review

22 June 2021

Why Should Nodule Cysteine-Rich (NCR) Peptides Be Absent From Nodules of Some Groups of Legumes but Essential for Symbiotic N-Fixation in Others?

J. Allan Downie

and

Eva Kondorosi

5,255 views

17 citations

Original Research

07 June 2021

Control of the Rhizobia Nitrogen-Fixing Symbiosis by Common Bean MADS-Domain/AGL Transcription Factors

Litzy Ayra

, 8 more and

Georgina Hernández

4,565 views

8 citations

Influence of inoculation on nodulation rate, content of leghemoglobin in nodules as well as nitrogen concentration in plant shoot. Soil samples were collected from two locations Fehrow and Müncheberg in Germany. Soybean was introduced in the soil with soybean history since 1–4 years or never introduced in the soil with no soybean history. The black bars represent the inoculated plant. Gray bars represent the non-inoculated plants. Stars (*) indicate a significantly different between inoculated and non-inoculated plants by the student’s t-test at the 5% level of significance. Numbers in brackets indicate the percentage difference mean, either higher or lower as shown, between inoculated and non-inoculated plants.

Original Research

04 June 2021

Soybean Nodulation Response to Cropping Interval and Inoculation in European Cropping Systems

Mosab Halwani

, 5 more and

Ralf Bloch

4,510 views

19 citations

Maximum likelihood phylogenetic tree based on concatenation of the nodC gene partial sequences of the strains Lut4, Llut5, Lcos6, and Llut8, isolated from nodules of L. cosentinii and L. luteus and related species within the genus Bradyrhizobium. Isolates are denoted in bold. Bootstrap values are indicated as percentages derived from 1000 replications. Values lower than 50 are not shown. Bar, 2 nucleotide substitution per 100 nucleotides. The original geographical origin of the species is shown in brackets. The tree is rooted with R. leguminosarum USDA 2370T.

Original Research

11 May 2021

Characterization of Bradyrhizobium spp. Nodulating Lupinus cosentinii and L. luteus Microsymbionts in Morocco

Mustapha Missbah El Idrissi

, 5 more and

Hanaa Abdelmoumen

3,326 views

7 citations

Original Research

22 April 2021

Non-specific Lipid Transfer Proteins in Legumes and Their Participation During Root-Nodule Symbiosis

Citlali Fonseca-García

, 2 more and

Carmen Quinto

3,402 views

10 citations

Nodulation parameters of S. supranubius after 6 months planted in the field (July sampling for n = 5). Average number of nodules (A), nodule dry weight (B), uprooted plant with nodules (C) and detail of nodules in situ (D). Boxes with letters are significantly different according to one-way ANOVA and LSD or T2-Tamhane post-hoc tests (p < 0.05).

Original Research

15 April 2021

Applying Agronomic Principles of Rhizobial Inoculation to the Conservation of a Keystone Legume Species in a High Mountain Ecosystem on an Oceanic Island

Laura Pulido-Suárez

, 4 more and

Milagros León-Barrios

2,045 views

3 citations

Review

11 March 2021

Will Phosphate Bio-Solubilization Stimulate Biological Nitrogen Fixation in Grain Legumes?

Walid Janati

, 4 more and

Adnane Bargaz

Interactions between PSB and legumes nodulated roots and their effects on nutrients availability and the overall plant growth parameters.

Biological nitrogen fixation (BNF) refers to a bacterially mediated process by which atmospheric N₂ is reduced, either symbiotically or non-symbiotically, into ammonia (NH₃) in the presence of the enzyme complex nitrogenase. In N₂-fixing grain legumes, BNF is often hampered under low phosphorus (P) availability. The P status of legumes, particularly nodules, as well as P availability in the rhizosphere, play a vital role in regulating BNF. Aside from increasing P availability via fertilization, other plant traits (i.e., extensive rooting system and their spatial distribution, hyper-nodulation, root exudates, rhizosphere acidification, and heterogeneity) contribute to greater P uptake and hence more effective BNF. The positive interaction between P availability and BNF can be exploited through beneficial soil P solubilizing microorganisms (PSM). These microorganisms can increase plant-available P by modifying either rhizosphere soil processes or promoting plant traits, which lead to increased P uptake by the production of plant growth-promoting substances, both of which could indirectly influence the efficiency of BNF in legumes. In this review, we report on the importance of microbial P bio-solubilization as a pathway for improving BNF in grain legumes via PSM and P solubilizing bacteria (PSB). Because BNF in legumes is a P-requiring agro-ecological process, the ability of soil PSB to synergize with the rhizobial strains is likely a key belowground process worth investigating for advanced research aiming to improve rhizosphere biological functions necessary for sustainable legume-based cropping systems.

9,784 views

27 citations