Nodulating bacteria from the family Rhizobiaceae are common in the semi-arid tropics around the world. The Brazilian semi-arid region extends over 95 million hectares of which only 3% is suitable for irrigation, therefore leaving an immense dryland area to be exploited by peasant farmers, who often lack appropriate technologies for sustainable management. Cowpea is an important crop in this area, representing the staple protein source for human nutrition. This work aimed to identify rhizobial strains capable of guaranteeing sufficient nitrogen derived from biological fixation for cowpea cultivated in dryland areas, evaluating not just efficiency but also the ecological parameters of competitiveness and survival in the soil. Grain yield and nodulation parameters showed that strain BR 3267 is capable of establishing efficient nodulation, improving both yield and total N accumulated in grain. Cowpea inoculated with strain BR 3267 showed grain productivity similar to plants receiving 50 kg of N per hectare, which is the amount of fertilizer commonly used in the north-east region. These characteristics associated with previously determined ecological properties makes strain BR 3267 an important resource for the optimization of biological nitrogen fixation in cowpea in the dryland areas of the semi-arid tropics. Data on the dynamics of rhizobial populations in such areas have shown that (1) the naturalized rhizobium population is very small and, by themselves, do not promote proper nodulation and, (2) the inoculant rhizobia do not persist between crops. Such characteristics represent an opportunity for the introduction of superior rhizobia strains, such as BR 3267, during the cowpea crop.

Contribution of biological nitrogen fixation to cowpea: a strategy for improving grain yield in the semi-arid region of Brazil

The symbiotic partnerships between legumes and their root-nodule bacteria (rhizobia) vary widely in their degree of specificity, but the underlying reasons are not understood. To assess the potential for host-range evolution, we have investigated microheterogeneity among the shared symbionts of a group of related legume species. Host specificity and genetic diversity were characterized for a soil population of Rhizobium leguminosarum biovar viciae (Rlv) sampled using six wild Vicia and Lathyrus species and the crop plants pea (Pisum sativum) and broad bean (Vicia faba). Genetic variation among 625 isolates was assessed by restriction fragment length polymorphism (RFLP) of loci on the chromosome (ribosomal gene spacer) and symbiosis plasmid (nodD region). Broad bean strongly favoured a particular symbiotic genotype that formed a distinct phylogenetic subgroup of Rlv nodulation genotypes but was associated with a range of chromosomal backgrounds. Host range tests of 80 isolates demonstrated that only 34% of isolates were able to nodulate V. faba. By contrast, 89% were able to nodulate all the local wild hosts tested, so high genetic diversity of the rhizobial population cannot be ascribed directly to the diversity of host species at the site. Overall the picture is of a population of symbionts that is diversified by plasmid transfer and shared fairly indiscriminately by local wild legume hosts. The crop species are less promiscuous in their interaction with symbionts than the wild legumes.

/pdf/diversity-and-specificity-of-rhizobium-leguminosarum-biovar-4dz628q9ju.pdf

Diversity and specificity of Rhizobium leguminosarum biovar viciae on wild and cultivated legumes.

The family Rhizobiaceae is comprised of six genera of plant-associating bacteria, Rhizobium, Bradyrhizobium, Sinorhizobium, Azorhizobium, Agrobacterium, and Phyllobacterium. A seventh genus, Mesorhizobium, has been proposed recently (Jarvis et al., 1997; Young and Haukka, 1996). In Bergey’s manual (Kersters and DeLey, 1984), the first four genera are distinguished from Agrobacterium and Phyllobacterium by their ability to form root- or stem-nodule symbioses with members of the plant family Leguminosae in which atmospheric nitrogen may be fixed into ammonia, and used by the host. On the other hand, many members of the genus Agrobacterium are described in Bergey’s manual as phytopathogenic, and are capable of producing hypertrophies, tumors, and abnormal root growth on diverse plant species.

Soil Biology of the Rhizobiaceae

Small farmers in the high Andes (> 2500 m) of Bolivia, Ecuador, and Peru face increasing threats to their livelihoods due to land degradation, climate change, and overall decreases in agricultural productivity. The fragile nature of these agroecosystems and limited capacity of resource-poor farmers in the region to adopt the large-scale use of conventional fertilizer and pest control technologies suggest the need for agroecological intensification to restore soil functioning and ensure long-term sustainability in these systems. This review addresses soil fertility decline from a management perspective and considers six basic approaches to enhance nutrient cycling, crop nutrient acquisition, and long-term productivity. A mass balance approach first defines basic boundaries for nutrient cycling and suggests that erosion control and identification of alternative nutrient sources (e.g., peri-urban wastes, rock phosphate) are critical for reversing negative nutrient budgets. Meanwhile, short-term nutrient dynamics could benefit greatly from improved management of organic residues in combination with low-level inorganic fertilizer applications. There is also a need for greater understanding of soil physiochemical properties throughout much of the Andes and the impacts of management. Similarly, soil biological functioning is critical for successful agroecological intensification and there is great potential for both inoculative and management strategies to promote beneficial soil communities. Crop breeding for smallholder environments should complement strategies of agroecological intensification, taking advantage of high regional agrobiodiversity and experience from stress breeding programs in other regions. Finally, we suggest several means by which the spatial and temporal organization of farms may be improved to enhance overall agroecosystem function.

Pathways to Agroecological Intensification of Soil Fertility Management by Smallholder Farmers in the Andean Highlands

Resumen pt: Este trabalho teve como objetivo avaliar a taxa de ocupacao nodular de estirpes de rizobio inoculadas em acessos de feijao-caupi (Vigna unguiculata (L.) ...

Especificidade simbiótica entre rizóbios e acessos de feijão-caupi de diferentes nacionalidades

An indirect, competitive, enzyme-linked immunosorbent assay (ELISA) was developed to indentify strains (SU391, SU303, WSM937, NZP5472) of Rhizobium leguminosarum bv. viciae in the nodules of Pisum sativum and Vicia faba and to study the effect of legume species and indigenous R. l. viciae on the nodulating-competitiveness of these strains, applied as seed inoculants. The study involved field-grown crops at Avondale and Merredin in Western Australia and Wagga Wagga in New South Wales. A multivariate statistical procedure was used to determine an optimal classification rule by which nodule isolates were allocated as an inoculant strain or indigenous strain. The legume significantly affected the proportion of nodules formed by inoculant strains at Merredin. Strains (SU303, WSM937 and NZP5472) with V. faba cv. Fiord were very competitive with indigenous rhizobia, forming 53–92% of the nodules. In comparison, inoculant strains on P. sativum at Merredin were found in 500 g−1 soil, the nodulating-competitiveness of inoculant strains applied to faba bean. No inoculant strain was remarkably better than another at competing with indigenous R. l. viciae. We conclude that seed inoculation often may be more successful with V. faba than P. sativum, which is fortuitous because indigenous R. l. viciae are more likely to be less efficient for N2 fixation with faba bean (cv. Fiord) than with pea. The relatively poor success with inoculation of P. sativum suggests the need to determine its efficiency for N2 fixation with indigenous R. l. viciae, and to ensure novel cultivars are effectively nodulated by these rhizobia. The poor representation of inoculant strains in nodules on faba bean grown in soils with very large numbers of soil-borne R. l. viciae may severely reduce its productivity. Moreover, we propose that seed inoculation may not achieve a solution to this problem.

Nodulation of field-grown Pisum sativum and Vicia faba: Competitiveness of inoculant strains of Rhizobium leguminosarum bv. viciae determined by an indirect, competitive ELISA method

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

A. Gregory

Author Tools

Chat about Author

Papers

Nodulation of field-grown Pisum sativum and Vicia faba: Competitiveness of inoculant strains of Rhizobium leguminosarum bv. viciae determined by an indirect, competitive ELISA method