Enhanced nodule initiation on alfalfa by wild-typeRhizobium meliloti co-inoculated withnod gene mutants and other bacteria

Caetano‐Anollés, Gustavo; Bauer, Wolfgang

doi:10.1007/bf00959525

Cited by 36 publications

(14 citation statements)

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“…It is known that lipo-chitin signals induce nodule formation and that they mimic endogenous plant growth regulators (19,53,58,61). Soil microorganisms such as Agrobacterium tumefaciens (13) or Bacillus subtilis (3) can also stimulate nodulation, through the production of bioactive molecules. This is supported by the observations that plant growth regulators like gibberellin and other plant hormones are produced by bacteria and actinomycetes (5-7, 28, 31).…”

Section: Discussionmentioning

confidence: 99%

Novel Plant-Microbe Rhizosphere Interaction Involving Streptomyces lydicus WYEC108 and the Pea Plant ( Pisum sativum )

Tokala

Strap

Jung

et al. 2002

Appl Environ Microbiol

355

204

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A previously undescribed plant-microbe interaction between a root-colonizing Streptomyces species, S. lydicus WYEC108, and the legume Pisum sativum is described. The interaction is potentially of great importance to the health and growth in nature of this nodulating legume. The root-colonizing soil actinomycete S. lydicus WYEC108 influences pea root nodulation by increasing root nodulation frequency, possibly at the level of infection by Rhizobium spp. S. lydicus also colonizes and then sporulates within the surface cell layers of the nodules. Colonization leads to an increase in the average size of the nodules that form and improves the vigor of bacteroids within the nodules by enhancing nodular assimilation of iron and possibly other soil nutrients. Bacteroid accumulation of the carbon storage polymer, poly-␤-hydroxybutyrate, is reduced in colonized nodules. Root nodules of peas taken from agricultural fields in the Palouse hills of northern Idaho were also found to be colonized by actinomycete hyphae. We hypothesize that root and nodule colonization is one of several mechanisms by which Streptomyces acts as a naturally occurring plant growth-promoting bacterium in pea and possibly other leguminous plants.Streptomyces lydicus WYEC108 is a root-colonizing actinomycete originally isolated and studied for its properties as an antifungal biocontrol agent. This strain is capable of mycoparasitic colonization of fungal root pathogens and excretion of antifungal metabolites within plant rhizospheres (16,62). Recently, we demonstrated that strain WYEC108 is also a plant growth-promoting bacterium in the absence of fungal pathogen challenge. This may be due to the ability of strain WYEC108 to produce hydroxamate-type siderophores and/or other plant growth-promoting metabolites in the rhizosphere (25). Streptomyces spp. have been previously described as rhizosphere-colonizing bacteria (37, 38), antifungal biocontrol agents useful in controlling fungal root diseases (51), in vitro siderophore producers, and in vitro producers of plant growthpromoting hormones (25). Plant root exudates stimulate rhizosphere growth of actinomycetes that are strongly antagonistic to fungal pathogens, while the actinomycetes utilize root exudates for growth and synthesis of antimicrobial substances (16,62). In addition, actinomycetes synthesize an array of biodegradative enzymes, including chitinases (9, 23, 35), glucanases (18,26,29,32,59,60), peroxidases (48), and other enzymes possibly involved in mycoparasitic activity. Yet, the overall importance, physiological activities, and symbiotic roles of actinomycetes in situ within plant rhizospheres remain little studied at the biochemical or mechanistic levels. We believe that Streptomyces are far more important rhizosphere bacteria than has been generally recognized.Important to the symbiotic relationship between plants and microbes is the acquisition of iron. Although abundant in nature, under aerobic conditions at a neutral or alkaline pH, iron is found in highly insoluble forms not readil...

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Section: Discussionmentioning

confidence: 99%

Novel Plant-Microbe Rhizosphere Interaction Involving Streptomyces lydicus WYEC108 and the Pea Plant ( Pisum sativum )

Tokala

Strap

Jung

et al. 2002

Appl Environ Microbiol

355

204

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“…Essa contribuição foi relacionada com a produção de fitormônios, pectinase ou sinais moleculares, em Bacillus cereus (Halverson & Handelsman, 1991), Azospirillum spp. (Singh & Rao, 1979;Plazinski & Rolfe, 1985;Andreeva et al, 1991), Agrobacterium (Caetano-Anollés & Bauer, 1988) e outras espécies de microrganismos (Omar & Abd-Alla, 1994).…”

unclassified

Nodulação e rendimento de soja co-infectada com Bacillus Subtilis e Bradyrhizobium Japonicum / Bradyrhizobium Elkanii

Araújo

Hungría

1999

Pesq. agropec. bras.

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Termos para indexação: controle biológico, fixação biológica do nitrogênio, Glycine max, inoculação, inoculante. SOYBEAN NODULATION AND YIELD WHEN CO-INOCULATED WITH BACILLUS SUBTILIS AND BRADYRHIZOBIUM JAPONICUM / BRADYRHIZOBIUM ELKANIIABSTRACT -Bacillus subtilis can improve rhizobial symbiotic performance by inhibiting plant pathogens or by the exudation of hormones. To verify the viability of co-inoculation of soybean seeds with Bradyrhizobium and Bacillus, three experiments were performed, in the State of Paraná, Brazil, in soils with established population of Bradyrhizobium. The Bradyrhizobium strains SEMIA 5019 and SEMIA 5080, and their natural variant strains tolerant to the metabolites of Bacillus were co-inoculated with two strains of Bacillus (AP-3 and PRBS-1), or their metabolites. In 1993/94, in Londrina, the coinoculation of Bradyrhizobium with formulated metabolites increased significantly, in relation to noninoculated control, nodule number (59%, stage V3), nodule occupancy by Bradyrhizobium strains carried on the inoculant (76%, R2) and soybean yield (24%); in Ponta Grossa, these increases were of 60%, 145% and 22%, respectively. Also in Londrina, the co-inoculation of the variant strains with crude metabolites of Bacillus has also increased yield (26%) and total N in grains (17%) and increases were verified by the co-inoculation of the Bradyrhizobium variant strains with Bacillus cells (78%). Consequently, the results have shown the viability of co-inoculating soybean seeds with crude or formulated metabolites, or with cells of Bacillus subtilis, to increase the contribution of the biological nitrogen fixation process.Index terms: biological control, biological nitrogen fixation, Glycine max, inoculation, inoculant. INTRODUÇÃONa cultura da soja, como na maioria das espécies cultivadas, o fornecimento de fertilizantes nitrogenados apresenta baixa eficiência de utilização por parte da planta, devido às perdas elevadas que ocorrem, particularmente por lixiviação e

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“…Thus, differences in the average number of nodules formed above the RT mark should be interpreted in terms of nodulation efficiency only where the inoculum dosage has been kept constant, as in Table II. The basis for this acropetal shift in nodule distribution is not known (10 (Table III). Nodules containing both parent and mutant were rare.…”

Section: Resultsmentioning

confidence: 99%

Role of Motility and Chemotaxis in Efficiency of Nodulation by Rhizobium meliloti

Caetano‐Anollés¹,

Wall²,

Micheli³

et al. 1988

Plant Physiol.

Self Cite

151

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Spontaneous mutants of Rhizobium mellot LS-30 defective in motility or chemotaxis were isolated and compared against the parent with respect to symbiotic competence. Each of the mutants was able to generate normal nodules on the host plant alfalfa (Medicago saliva), but had slightly delayed nodule formation, diminished nodulation in the initially susceptible region of the host root, and relatively low representation in nodules following co-inoculation with equal numbers of the parent. When inoculated in growth pouches with increasing dosages of the parental strain, the number of nodules formed in the initially susceptible region of the root increased sigmoidally, with an optimum concentration of about 105 to 106 bacteria/ plant. The dose-response behavior of the nonmotile and nonchemotactic mutants was similar, but they required 10-to 30-fold higher concentrations of bacteria to generate the same number of nodules. The distribution frequencies of nodules at different positions along the primary root were very similar for the mutants and parent, indicating that reduced nodulation by the mutants in dose-response experiments probably reflects reduced efficiency of nodule initiation rather than developmentally delayed nodule initiation. The number of bacteria that firmly adsorbed to the host root surface during several hours of incubation was 5-to 20-fold greater for the parent than the mutants. The mutants were also somewhat less effective than their parent as competitors in root adsorption assays. It appears that motility and chemotaxis are quantitatively important traits that facilitate the initial contact and adsorption of symbiotic rhizobia to the host root surface, increase the efficiency of nodule initiation, and increase the rate of infection development.Soil bacteria belonging to the genus Rhizobium induce the formation of symbiotic nitrogen-fixing nodules on the roots of leguminous plants. The establishment of an effective nodule occurs through a complex sequence of interactions which may begin even prior to physical contact between the partners (4,5,29). Rhizobia are initially attracted to the developing roots, where they adsorb to the root surface and elicit root hair deformation, cortical cell division and the formation of an infection thread which carries the bacterial symbiont into the root cortex.

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Enhanced nodule initiation on alfalfa by wild-typeRhizobium meliloti co-inoculated withnod gene mutants and other bacteria

Cited by 36 publications

References 36 publications

Novel Plant-Microbe Rhizosphere Interaction Involving Streptomyces lydicus WYEC108 and the Pea Plant ( Pisum sativum )

Novel Plant-Microbe Rhizosphere Interaction Involving Streptomyces lydicus WYEC108 and the Pea Plant ( Pisum sativum )

Nodulação e rendimento de soja co-infectada com Bacillus Subtilis e Bradyrhizobium Japonicum / Bradyrhizobium Elkanii

Role of Motility and Chemotaxis in Efficiency of Nodulation by Rhizobium meliloti

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