Cation and phosphate influences on the nodulating characteristics of indigenous serogroups of Rhizobium trifolii on soil grown Trifolium subterraneum L.

Almendras, A.; Bottomley, Peter J.

doi:10.1016/0038-0717(88)90015-6

Cited by 9 publications

(4 citation statements)

References 33 publications

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“…Despite the importance of subclover to the productivity of a large area of pastures on hill and range lands in the far western United States, there have been several previous reports which have shown that field-grown subclover in this region is nodulated primarily by rhizobia that exhibit suboptimal symbiotic effectiveness (13,25,27,30). Furthermore, agronomists have reported that the N content of subclover herbage grown throughout Oregon and California is erratic and can range from 2 to 4.5% (1,16,31,40,45). Our observations that the nodule-dominant isolates on the Abiqua soil site fix 2to 10-fold less N2 on subclover than minor occupants fix and produce first-harvest herbage that has suboptimal protein concentrations complement the observations described above.…”

Section: Discussionmentioning

confidence: 99%

Symbiotic Characteristics of Rhizobium leguminosarum bv. trifolii Isolates Which Represent Major and Minor Nodule-Occupying Chromosomal Types of Field-Grown Subclover ( Trifolium subterraneum L.)

Leung

Wanjage

Bottomley

1994

Appl Environ Microbiol

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The symbiotic effectiveness and nodulation competitiveness of Rhizobium leguminosarum bv. trifolii soil isolates were evaluated under nonsoil greenhouse conditions. The isolates which we used represented both major and minor nodule-occupying chromosomal types (electrophoretic types [ETs]) recovered from fieldgrown subclover (Trifolium subterraneum L.). Isolates representing four ETs (ETs 2, 3, 7, and 8) that were highly successful field nodule occupants fixed between 2-and 10-fold less nitrogen and produced lower herbage dry weights and first-harvest herbage protein concentrations than isolates that were minor nodule occupants of field-grown plants. Despite their equivalent levels of abundance in nodules on field-grown subclover plants, ET 2 and 3 isolates exhibited different competitive nodulation potentials under nonsoil greenhouse conditions. ET 3 isolates generally occupied more subclover nodules than isolates belonging to other ETs when the isolates were mixed in 1:1 inoculant ratios and inoculated onto seedlings. In contrast, ET 2 isolates were less successful at nodulating under these conditions. In many cases, ET 2 isolates required a numerical advantage of at least 6:1 to 11:1 to occupy significantly more nodules than their competitors. We identified highly effective isolates that were as competitive as the ET 3 isolates despite representing serotypes that were rarely recovered from nodules of field-grown plants. When one of the suboptimally effective isolates (ET2-1) competed with an effective and competitive isolate (ET31-5) at several different inoculant ratios, the percentages of nodules occupied by the former increased as its numerical advantage increased. Although subclover yields declined as nodule occupancy by ET2-1 increased, surprisingly, this occurred at inoculant ratios at which large percentages of nodules were still occupied by ET31-5.

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Section: Discussionmentioning

confidence: 99%

Symbiotic Characteristics of Rhizobium leguminosarum bv. trifolii Isolates Which Represent Major and Minor Nodule-Occupying Chromosomal Types of Field-Grown Subclover ( Trifolium subterraneum L.)

Leung

Wanjage

Bottomley

1994

Appl Environ Microbiol

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“…All previous immunofluorescence studies of soilborne rhizobia have involved the use of 0.4-p.m-pore-size filters to collect the bacterial cells (16,29). Our initial discovery of small biovar trifolii organisms led us to suggest that 0.2-pLm-pore-size filters, commonly used by aquatic microbial ecologists, might be necessary for accurate population determinations (2). While this has been confirmed because of the extensive and variable contribution of small cells to serogroup populations, the lack of nodulating ability in this subpopulation mollifies this concern when competitive nodulation is the primary focus.…”

Section: Discussionmentioning

confidence: 99%

Population Size and Distribution of Rhizobium leguminosarum bv. trifolii in Relation to Total Soil Bacteria and Soil Depth

Bottomley

Dughri

1989

Appl Environ Microbiol

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Bacterial cells small enough to pass through 0.4-,um-pore-size filters made up 5 to 9% of the indigenous bacterial population in 0to 20-cm-depth samples of Abiqua silty clay loam. Within the same soil samples, cells of a similar dimension were stained with fluorescent antibodies specific to each of four antigenically distinct indigenous serogroups of Rhizobium leguminosarum bv. trifolii and made up 22 to 34% of the soil population of the four serogroups. Despite the extensive contribution of small cells to these soil populations, no evidence of their being capable of either growth or nodulation was obtained. The density of soil bacteria which could be cultured ranged between 0.5 and 8.5% of the >0.4-p.m direct count regardless of media, season of sampling, or soil depth. In the same soil samples, the viable nodulating populations of biovar trifolii determined by the plant infection soil dilution technique ranged between 1 and 10% of the >0.4-p.m direct-immunofluorescence count of biovar trifolii. The <0.4-p.m cell populations of both total soil bacteria and biovar trifolii changed abruptly between the 10to 15-cm and 15to 20-cm soil depth increments, increasing from 5 to 20% and from 20 to 50%, respectively, of their direct-count totals. The increase in density of the small-cell population corresponded to a significant increase in soil bulk density (1.07 to 1.21 g cm-3). The percent contribution of the <0.4-p.m direct count to individual serogroup totals increased with soil depth by approximately 2-fold (39 to 87%) for serogroups 17 and 21 and by 12-fold (6 to 75%) for serogroups 6 and 36.

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“…Gibson (1977), Munns and Francop (1982), Freire (1984) and Ladha et al (1992) have reviewed the soil constraints to symbiotic performance. Major considerations affecting either the microbe, the host, or their symbiotic interaction include soil acidity (Munns, 1977), other acid-related factors including aluminum and manganese toxicity, and calcium deficiency (Singer and Munns, 1987), phosphorus (Almendras and Bottomley 1988;Cassman et al, 1981;Helyar and Munns, 1975;Keyser and Munns, 1979;Leung and Bottomley, 1987;Munns, 1979;Singleton et al, 1985), calcium Munns, 1984, 1985), salinity (Singleton and Bohlool, 1983) and flooding . Symbiotic activity within a plant community is also conditioned by the amount of N mineralized from organic sources (George et al, 1988).…”

Section: Environmental Constraintsmentioning

confidence: 99%

“…Environmental influences such as soil temperature (Weber and Miller, 1972), or additions of P and K (Almendras and Bottomley, 1988) can alter competition patterns.…”

Section: Environmental Constraintsmentioning

confidence: 99%

Biological nitrogen fixation for sustainable agriculture: A perspective

et al. 1992

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The economic and environmental costs of the heavy use of chemical N fertilizers in agriculture are a global concern. Sustainability considerations mandate that alternatives to N fertilizers must be urgently sought. Biological nitrogen fixation (BNF), a microbiological process which converts atmospheric nitrogen into a plant-usable form, offers this alternative. Nitrogen-fixing systems offer an economically attractive and ecologically sound means of reducing external inputs and improving internal resources. Symbiotic systems such as that of legumes and Rhizobium can be a major source of N in most cropping systems and that of Azolla and Anabaena can be of particular value to flooded rice crop. Nitrogen fixation by associative and free-living microorganisms can also be important. However, scientific and socio-cultural constraints limit the utilization of BNF systems in agriculture. While several environmental factors that affect BNF have been studied, uncertainties still remain on how organisms respond to a given situation. In the case of legumes, ecological models that predict the likelihood and the magnitude of response to rhizobial inoculation are now becoming available. Molecular biology has made it possible to introduce choice attributes into nitrogen-fixing organisms but limited knowledge on how they interact with the environment makes it difficult to tailor organisms to order. The difficulty in detecting introduced organisms in the field is still a major obstacle to assessing the success or failure of

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Cation and phosphate influences on the nodulating characteristics of indigenous serogroups of Rhizobium trifolii on soil grown Trifolium subterraneum L.

Cited by 9 publications

References 33 publications

Symbiotic Characteristics of Rhizobium leguminosarum bv. trifolii Isolates Which Represent Major and Minor Nodule-Occupying Chromosomal Types of Field-Grown Subclover ( Trifolium subterraneum L.)

Symbiotic Characteristics of Rhizobium leguminosarum bv. trifolii Isolates Which Represent Major and Minor Nodule-Occupying Chromosomal Types of Field-Grown Subclover ( Trifolium subterraneum L.)

Population Size and Distribution of Rhizobium leguminosarum bv. trifolii in Relation to Total Soil Bacteria and Soil Depth

Biological nitrogen fixation for sustainable agriculture: A perspective

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