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Allan R. J. Eaglesham

Bio: Allan R. J. Eaglesham is an academic researcher from Boyce Thompson Institute for Plant Research. The author has contributed to research in topics: Rhizobia & Rhizobium. The author has an hindex of 14, co-authored 27 publications receiving 758 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the amounts of N fixed in the field in Nigeria by four cowpea and two soybean cultivars were determined at different levels of available N by the difference and the "AN"-value methods using non-nodulating soybean, maize and celosia as nonfixing controls.
Abstract: SummaryThe amounts of N fixed in the field in Nigeria by four cowpea and two soybean cultivars were determined at different levels of available N by the difference and the ‘AN’-value methods using non-nodulating soybean, maize and celosia as non-fixing controls. No significant differences were found between the two methods or with different controls. Grain removal and return of residues to the soil were measured and net soil-N changes calculated. N-benefits accrued from two of the cowpea cultivars when grown at low mineral-N levels, but with higher mineral-N availability, no cultivar contributed N because of inhibition of nodulation and lowered N2-fixation. Although the soybeans fixed more N than the cowpeas they caused greater net N-depletions because they sequestered a greater fraction of N in the grain.

75 citations

Journal ArticleDOI
TL;DR: Although the physiological characteristics of FGR.
Abstract: Physiological and symbiotic characteristics were identified in fast-growing (FG)Rhizobium japonicum. Carbon nutritional patterns linked these rhizobia to other FG rhizobia. They were able to use hexoses, pentoses, disaccharides, trioses, and organic acids for growth, but they were unable to use dulcitol or citrate. These rhizobia produced acid with all carbon sources except intermediates of the Krebs cycle. FGR. japonicum showed no vitamin requirements and were tolerant to 1% NaCl but not to 2%. They nodulated cowpea, pigeon pea, and mung bean but not peanut. Effective, nitrogen-fixing symbioses were observed only with cowpea and pigeon pea. In addition, FGR. japonicum formed effective symbioses with Asian-type soybeans. We concluded that although the physiological characteristics of FGR. japonicum were similar to other FG rhizobia, their symbiotic properties were similar to slow-growing rhizobia of the cowpea miscellany.

67 citations

Book ChapterDOI
01 Jan 1990
TL;DR: A photosynthetic rhizobium that could meet directly its energy needs for biological N2 fixation could be advantageous since the legume plant might use the saved fixed carbon to produce additional harvestable plant product.
Abstract: Biological N2 fixation requires large amounts of energy based on either in vitro biochemical studies of nitrogenase or in vivo studies of root nodulated legume plants. For example, calorimetric experiments with effectively root nodulated soybeans suggest that the aerobic metabolism of the equivalent of about 12 g of carbohydrate to CO2 and H2O is required to fix 1 g of N2 by the rhizobial-legume process (11). This carbohydrate is provided through foliar photosynthesis by the legume macrosymbiont and is used by the rhizobial microsymbiont. A photosynthetic rhizobium that could meet directly its energy needs for biological N2 fixation could be advantageous since the legume plant might use the saved fixed carbon to produce additional harvestable plant product.

51 citations

Journal ArticleDOI
TL;DR: Broad ranges of serological diversity were found in the rhizobia at each location, moreover each population had its own general characteristics, and ELISA reactivity correlated with colony morphology but not with nodulation potential.
Abstract: To appraise the usefulness of the enzyme-linked immunosorbent assay (ELISA) technique for examining the serological diversity of slow-growing rhizobia, twelve diverse strains from three countries were examined with four antisera. Eleven of the strains were from the “cowpea” miscellany, and the twelfth was a Rhizobium japonicum strain. Some “cowpea” strains showed no antigenic relatedness with each other while others were closely related, and some showed a greater affinity with the R. japonicum strain than with other “cowpea” strains. All of the strains showed antigenic homology to an isolate from a wild Arachis sp., while two strains isolated from adjacent plants of the same cultivar had little homology. These patterns ofrelatedness and diversity clearly demonstrated the utility of the ELISA method, and so it was used to examine 53 strains isolated from cowpeas grown at three West African locations, Maradi (Niger), Ibadan and Onne (Nigeria). Broad ranges of serological diversity were found in the rhizobia at each location, moreover each population had its own general characteristics. Maradi strains were highly reactive with the five antisera used, Onne strains less so, and Ibadan strains even less so. ELISA reactivity correlated with colony morphology but not with nodulation potential.

47 citations


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Journal ArticleDOI
TL;DR: The Rhizobium-legume (herb or tree) symbiosis is suggested to be the ideal solution to the improvement of soil fertility and the rehabilitation of arid lands and is an important direction for future research.
Abstract: Biological N2 fixation represents the major source of N input in agricultural soils including those in arid regions. The major N2-fixing systems are the symbiotic systems, which can play a significant role in improving the fertility and productivity of low-N soils. The Rhizobium-legume symbioses have received most attention and have been examined extensively. The behavior of some N2-fixing systems under severe environmental conditions such as salt stress, drought stress, acidity, alkalinity, nutrient deficiency, fertilizers, heavy metals, and pesticides is reviewed. These major stress factors suppress the growth and symbiotic characteristics of most rhizobia; however, several strains, distributed among various species of rhizobia, are tolerant to stress effects. Some strains of rhizobia form effective (N2-fixing) symbioses with their host legumes under salt, heat, and acid stresses, and can sometimes do so under the effect of heavy metals. Reclamation and improvement of the fertility of arid lands by application of organic (manure and sewage sludge) and inorganic (synthetic) fertilizers are expensive and can be a source of pollution. The Rhizobium-legume (herb or tree) symbiosis is suggested to be the ideal solution to the improvement of soil fertility and the rehabilitation of arid lands and is an important direction for future research.

1,542 citations

Journal ArticleDOI
TL;DR: It is surmised that plants secrete blends of compounds and specific phytochemicals in the root exudates that are differentially produced at distinct stages of development to help orchestrate rhizosphere microbiome assemblage.
Abstract: There is a concerted understanding of the ability of root exudates to influence the structure of rhizosphere microbial communities. However, our knowledge of the connection between plant development, root exudation and microbiome assemblage is limited. Here, we analyzed the structure of the rhizospheric bacterial community associated with Arabidopsis at four time points corresponding to distinct stages of plant development: seedling, vegetative, bolting and flowering. Overall, there were no significant differences in bacterial community structure, but we observed that the microbial community at the seedling stage was distinct from the other developmental time points. At a closer level, phylum such as Acidobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria and specific genera within those phyla followed distinct patterns associated with plant development and root exudation. These results suggested that the plant can select a subset of microbes at different stages of development, presumably for specific functions. Accordingly, metatranscriptomics analysis of the rhizosphere microbiome revealed that 81 unique transcripts were significantly (P<0.05) expressed at different stages of plant development. For instance, genes involved in streptomycin synthesis were significantly induced at bolting and flowering stages, presumably for disease suppression. We surmise that plants secrete blends of compounds and specific phytochemicals in the root exudates that are differentially produced at distinct stages of development to help orchestrate rhizosphere microbiome assemblage.

987 citations

Journal ArticleDOI
TL;DR: In this paper, a comprehensive summary and interpretation of these interactions with specific emphasis on high yield environments is lacking. But the results from many N fertilization studies are often confounded by insufficiently optimized BNF or other management factors that may have precluded achieving BNF-mediated yields near the yield potential ceiling.

831 citations

Book ChapterDOI
TL;DR: In this article, the authors described the various aspects of cereal-legume intercropping systems Intercropping is the growing of two or more crop species simultaneously in the same field during a growing season.
Abstract: Publisher Summary This chapter describes the various aspects of cereal-legume intercropping systems Intercropping is the growing of two or more crop species simultaneously in the same field during a growing season The intercropping of legumes with cereals offers scope for developing energy-efficient and sustainable agriculture The main types of intercropping include mixed intercropping, row intercropping, and strip intercropping Crop combinations differ with geographical location and there may be intercropping of tree crops, intercropping of tree and field crops, or intercropping of field crops Combinations of crops are determined primarily by the length of the growing season and the adaptation of crops to particular environments Different indices have been suggested for evaluating productivity and efficiency per unit area of land of cereal-legume intercrop systems These include comparisons of absolute yields, protein yields, caloric equivalent, and in economic terms, gross returns from intercrops and sole crops Differences in competitive ability affect the relative performance of component crops and thus the land equivalent ratio values of different cereal-legume intercrop systems It is found that phosphorus is a major nutrient that determines the production potential of most grain legumes usually intercropped with cereals

738 citations

Book ChapterDOI
TL;DR: In this paper, a review reveals that crop residues of common cultivated crops are an important resource not only as a source of significant quantities of nutrients for crop production but also affecting soil physical, chemical, and biological functions and properties and water and soil quality.
Abstract: This review reveals that crop residues of common cultivated crops are an important resource not only as a source of significant quantities of nutrients for crop production but also affecting soil physical, chemical, and biological functions and properties and water and soil quality. When crop residues are returned to the soils, their decomposition can have both positive and negative effects on crop production and the environment. Our aim as agricultural scientists is to increase the positive effects. This can only be achieved with the better understanding of residue, soil, and management factors and their interactions, which affect the decomposition and nutrient release processes. Data on nitrogen benefits and nitrogen recoveries from residues show that a considerable potential exists from residues, especially leguminous residues, not only in meeting the N demands of the succeeding crops, but also in increasing the long-term fertility of the soils. In addition, crop residues and their proper management affects the soil quality either directly or indirectly. Intensive cropping systems are very diverse and complex, so no one residue management system is superior under all situations. Ideally, crop residue management practices should be selected to enhance crop yields with a minimum adverse effect on the environment. It is suggested that in each cropping system, the constraints to production and sustainability should be identified and conceptualized to guide toward the best option. Multidisciplinary and integrated efforts by soil scientists, agronomists, ecologists, environmentalists, and economists are needed to design a system approach for the best choice of crop residue management system to enhance both agricultural productivity and sustainability.

673 citations