scholarly journals The Symbiotic Synthesis of Auxin by Legumes and Nodule Bacteria and its Eole in Nodule Development

1960 ◽  
Vol 13 (4) ◽  
pp. 456 ◽  
Author(s):  
NP Kefford ◽  
J Brockwell ◽  
JA Zwar
Keyword(s):  
Acetic Acid ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Nodule Development ◽  
Distilled Water ◽  
Rhizobium Trifolii ◽  
Nodule Bacteria ◽  
Root Medium ◽  
Growth Properties ◽  
Indole 3 Acetic Acid

When subterranean clover (Trifolium subterraneum L.) plants were grown for 3 weeks over distilled water, tryptophan could be detected in the root medium of both sterile cultures and those inoculated with Rhizobium trifolii 3 days earlier. Auxin could be detected only in the inoculated medium. The auxin had the chromatographic and growth properties of indole�3-acetic acid (IAA). Since nodule bacteria produce auxin only in the presence of tryptophan, which is a probable precursor of lAA, it is suggested that the tryptophan exuded by clover roots is converted to lAA by nodule bacteria. Auxin was still produced in the root medium when strains of Rhizobium which do not nodulate subterranean olover roots were used as inooulant, or when nitrate, which delays nodulation, was present in the medium.

The in vitro inhibition of Phytophthora clandestina by some rhizobia and the possible role of Rhizobium trifolii in biological control of Phytophthora root rot of subterranean clover

1999 ◽  
Vol 50 (8) ◽  
pp. 1469 ◽  
Author(s):  
S. Simpfendorfer ◽  
T. J. Harden ◽  
G. M. Murray
Keyword(s):  
Biological Control ◽  
Root Rot ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Root Disease ◽  
Rhizobium Trifolii ◽  
Biological Control Agents ◽  
Control Activity ◽  
Phytophthora Root Rot

The interaction between 29 isolates of Rhizobium and the in vitro growth of 3 strains of Phytophthora clandestina was investigated to determine the potential of these bacteria as biological control agents against root rot of subterranean clover (Trifolium subterraneum L.). The biological control activity of Rhizobium on the severity of root disease in seedlings was also investigated under glasshouse conditions. Thirteen of the 29 Rhizobium isolates caused significant reductions in the hyphal growth of the 3 P. clandestina isolates examined. Inoculation of seedlings with Rhizobium trifolii reduced the severity of root disease by 14–58% with corresponding increases in dry matter production of 20–73%. These results indicate that Rhizobium species have potential as biological control agents against the root rot of T. subterraneum seedlings caused by P. clandestina.

Rhizosphere relationships of subterranean clover. I. Interactions between strains of Rhizobium trifolii.

1954 ◽  
Vol 5 (2) ◽  
pp. 247 ◽  
Author(s):  
JR Harris
Keyword(s):  
Nitrogen Fixation ◽  
Host Plant ◽  
Root Zone ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Rhizobium Trifolii ◽  
Rhizobial Strain ◽  
Susceptible Host ◽  
Active Elements ◽  
Indigenous Microflora

A study was made of a number of effective and ineffective strains of Rhizobium trifolii in association with subterranean clover (Trifolium subterraneum L.), variety Bacchus Marsh. Where these were inoculated singly into sterilized soils in pot experiments conducted in the greenhouse, typical effective, ineffective, or intermediate plant reactions were obtained. Where more than one strain was inoculated, competition between strains took place and was reflected in nodule pattern and plant reaction. Some strains consistently failed to produce appreciable nodules in the presence of other rhizobia, some showed modification to varying degrees, and some were unaffected. Such behaviour was found to be closely linked with the ability of the strain to proliferate in the rhizosphere of the host plant, and placement of inoculum was shown to influence plant reaction. The concept of "incursion" as a property of a rhizobial strain is suggested. An incursive strain is one able to migrate from the initial site of inoculation and establish an adequate population in the root zone of the susceptible host despite the presence of active elements of the indigenous microflora and microfauna, including antagonistic and predatory forms. The property of incursion is independent of considerations of efficiency of nitrogen fixation or virulence for the host plant. Strains of rhizobia which are poorly incursive may fail to infect the host upon which they have been inoculated if subject to competition from indigenous rhizobia already established in the soil. The necessity of assessing properties of virulence and incursion as well as efficiency of nitrogen fixation in selecting rhizobia for purposes of commercial inoculation is stressed, and the methods of making such tests are discussed.

Competition between effective and ineffective strains of Rhizobium trifolii in the nodulation of Trifolium subterraneum

1969 ◽  
Vol 20 (5) ◽  
pp. 827 ◽  
Author(s):  
AC Robinson
Keyword(s):  
Competitive Ability ◽  
Root Nodule ◽  
Effective Strain ◽  
Substantial Reduction ◽  
Trifolium Subterraneum ◽  
Bacterial Cells ◽  
Rhizobium Trifolii ◽  
Parallel Study ◽  
Nodule Bacteria ◽  
Tube Culture

The competitive ability of effective and ineffective strains of Rhizobium trifolii to form nodules on two cultivars of Trifolium subterraneum was examined under bacteriologically controlled conditions in tube culture. Seedlings were inoculated with mixtures of known numbers each of effective and of ineffective strains and the strains forming the nodules subsequently determined. In all instances, the effective strains formed a much greater proportion of nodules than would be expected from the relative numbers of each strain in the inoculum. Moreover, a reduction in the numbers of an effective strain relative to the numbers of an ineffective strain failed to result in a corresponding increase in the proportion of nodules formed by an ineffective strain. Instead, the ratio of ineffective to effective strains had to be of the order of 108/104 or wider (c. 10,000/1) before there was a substantial reduction in the number of nodules formed by the effective strains. Even when this ratio was of the order of 108/102, the effective strains still produced some of the nodules. A parallel study of the rates of nodulation of seedlings inoculated with mixtures of strains showed that these rates were characteristic of the proportions of nodules being formed by each strain. Subsequently seedlings were inoculated with mixtures of effective and ineffective strains, and after 66, 90, and 114 hr the roots were surface-sterilized and their contents isolated and identified. Independently of the mixture of strains used, most of the bacterial cells were identified as the effective strains. Because the strains of effective and ineffective bacteria used produce nodules freely when inoculated separately onto these hosts, it is postulated that the hosts distinguished between effective and ineffective strains, and that this recognition is related to compatibility in association with the host. The significance of the results in relation to studies of the root-nodule bacteria is discussed.

The effect of anti-fungal antibiotics on the nodulation of Trifolium subterraneum and the estimation of Rhizobium trifolii populations

1968 ◽  
Vol 8 (32) ◽  
pp. 327 ◽  
Author(s):  
AC Robinson
Keyword(s):  
Pure Culture ◽  
Culture Media ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Test Plant ◽  
Rhizobium Trifolii ◽  
Plant Infection ◽  
Micro Organisms ◽  
Anti Fungal ◽  
Test Plants

Three anti-fungal antibiotics (cycloheximide, griseofulvin, and mycostatin) were tested for their effects on inoculated Trifolium subterraneum (subterranean clover). All three influenced the growth and nodulation of the test plant, the effects being least with mycostatin. Mycostatin was further examined for its effect on a plant-infection technique for estimating Rhizobium numbers. The presence in culture media of mycostatin did not impair the accuracy of the plant-infection test for counting rhizobia in a pure culture. Moreover, when the plant-infection technique was used for counting rhizobia in soil, the antibiotic reduced the amount of infection of the test plant by miscellaneous soil micro-organisms, thereby improving nodulation. It is concluded that the incorporation of mycostatin into media (100 p.p.m.) used for growing test plants in plant-infection tests will improve the reliability of the method.

Variation in symbiotic effectiveness in subterranean clover (Trifolium subterraneum L.)

1961 ◽  
Vol 12 (2) ◽  
pp. 212 ◽  
Author(s):  
PS Nutman
Keyword(s):  
Hybrid Material ◽  
Bacterial Strain ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Symbiotic Effectiveness ◽  
Nodule Bacteria ◽  
Strain Specificity

(1) The symbiotic effectiveness of 15 varieties and of four tetraploid lines of subterranean clover were examined in association with several strains of nodule bacteria.(2) Relatively- small but significant differences in yield occurred between host' varieties, and the varietal order of response depended somewhat on the bacterial strain, but not enough to shorn- any well-defined variety-strain specificity. (3) Hybridization between varieties increased yields slightly in F2, less in F3, and the effect disappeared in F4. (4) With one doubtful exception all attempts to alter effectiveness by selection or breeding within hybrid material failed.

Indole-3-acetic acid production by cell-free extracts of Rhizobium trifolii

1984 ◽  
Vol 16 (6) ◽  
pp. 677-678 ◽  
Author(s):  
T. García-Rodríguez ◽  
C. Alvarez ◽  
J. Pérez-Silva
Keyword(s):  
Acetic Acid ◽  
Acid Production ◽  
Rhizobium Trifolii ◽  
Acetic Acid Production ◽  
Indole 3 Acetic Acid

Host selection for effective Rhizobium trifolii by red clover and subterranean clover in the field

1969 ◽  
Vol 20 (6) ◽  
pp. 1053 ◽  
Author(s):  
AC Robinson
Keyword(s):  
Host Selection ◽  
Root Nodule ◽  
Red Clover ◽  
Subterranean Clover ◽  
Mixed Population ◽  
Rhizobium Trifolii ◽  
Nodule Bacteria ◽  
Heterologous Host ◽  
Selection For ◽  
Test Plants

Cultures of root-nodule bacteria, from the nodules of red clover and subterranean clover growing closely together in the field, were tested for comparative symbiotic ability (effectiveness) with both red clover and subterranean clover. It was found that test plants of either host species nodulated faster and more effectively when inoculated with cultures isolated from the homologous host growing in the field than did test plants inoculated with cultures isolated from the heterologous host. Because the hosts had originally been nodulated in the presence of the same field populations of Rhizobium trifolii, it is concluded that the host legume exerts a selective effect in accepting infections from a mixed population.

Symbiotic competence of Trifolium subterraneum lines of low oestrogenic isoflavone content

1970 ◽  
Vol 10 (46) ◽  
pp. 555 ◽  
Author(s):  
J Brockwell ◽  
AC Robinson
Keyword(s):  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Rhizobium Trifolii ◽  
Isoflavone Content ◽  
Low Levels ◽  
Better Than

Twenty-nine lines of subterranean clover (Trifolium subterraneum), mostly selected for low levels of oestrogenic isoflavones, were inoculated with seven effective strains of Rhizobium trifolii. They were grown at two different root temperatures and their performances compared with those of the subterraneum clover cultivar, Tallarook. Ten criteria were used to assess symbiotic competence. No line was inferior to Tallarook in all ten criteria, but one line was inferior in nine of the ten, three in seven of the ten and fifteen others were poorer than Tallarook in one to six criteria. Of the ten lines whose symbiotic performances were as good as or better than Tallarook, a number also had low isoflavone levels, but there was no evidence to suggest that symbiotic competence was related to isoflavone content. It is concluded that it will be necessary to exercise caution in the agronomic or breeding use of lines Which are not consistently symbiotically competent.

The relationship between the phosphorus status of subterranean clover plants and the dry weight responses of detached leaves in solutions with and without phosphate

1976 ◽  
Vol 27 (1) ◽  
pp. 53 ◽  
Author(s):  
D Bouma ◽  
EJ Dowling
Keyword(s):  
Diagnostic Technique ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Dry Weight ◽  
Distilled Water ◽  
Total Light ◽  
Detached Leaves ◽  
Preceding Period ◽  
Phosphate Treatment ◽  
The Relationship

In four experiments subterranean clover plants (Trifolium subterraneum L., cv. Mt. Barker) were grown at different levels of phosphorus applied to solution cultures, to Perlite and to pots containing phosphorus-deficient soil. Leaves detached from deficient plants, placed in 3mM fructose 1,6-diphosphate or in 6mM NaH2PO4.2H2O for periods of 8–12 hr and then in distilled water under fluorescent lights (31,000–33,000 lx) for total light periods of 75–115 hr (18 hr light per 24 hr), showed greater increases in dry weight than corresponding leaves placed in distilled water without an initial phosphate treatment. By contrast, there were no differences in dry weight increases between similarly treated leaves from non-deficient plants; thus a clear distinction could be made between deficient and non-deficient plants. Dry weight increases of deficient leaves during the light period were markedly dependent on the length of the preceding period in phosphate solutions. Maximum increases occurred after periods of 8–12 hr, depending on the degree of phosphorus stress of the leaves. For non-deficient leaves initial uptake periods of up to 12 hr gave dry weight increases under the lights close to or the same as those of leaves in distilled water only, while periods of 24 and 48 hr resulted in greatly reduced dry weight increases. The possible application of the results as the basis for a simple diagnostic technique is discussed.

Soil acidity and Rhizobium: their effects on nodulation of subterranean clover on the slopes of southern New South Wales

1988 ◽  
Vol 39 (4) ◽  
pp. 605 ◽  
Author(s):  
J Evans ◽  
Z Hochman ◽  
GE O'Connor ◽  
GJ Osborne
Keyword(s):  
N2 Fixation ◽  
Soil Acidity ◽  
New South ◽  
New South Wales ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Rhizobium Trifolii ◽  
South Wales ◽  
Rate Of Increase ◽  
Limed Soil

Rhizobium trifolii and root nodulation were compared in acid and limed soil to investigate mechanisms by which current soil acidity on the slopes of southern New South Wales may reduce the growth of Trifolium subterraneum. Increasing soil pH increased both the rate at which Rhizobium trifolii colonized soil and the frequency of nodules/g root (NF). Thus, numbers of R. trifolii were greater in carbonate-treated soil throughout autumn and winter compared to unlimed soil. In limed soil R. trifolii were measured at 104-105/g soil as early as seedling germination, 40-200 x more than in unlimed soil. Despite this, by spring, the numbers of rhizobia in soil without lime reached large and even similar levels as occurred in limed soil. Subsequently, with the drying of soil in summer, the numbers of R. trifolii declined markedly in both untreated and limed soil. Maximum NF could not be achieved with addition of Ca without increase in pH. From the field observations and other research, a hypothetical model is proposed to explain how differences in the rates of change in rhizobial numbers due to acidity may determine nodulation (NF). Thus, it is suggested that, when there is a repetitive decline in numbers of R. trifolii to low levels in summer, their subsequent rate of increase in the following autumn influences nodule abundance. The production of DM in an acidic soil appeared to be limited by symbiotic N2 fixation since added N fertilizer removed lime response. The limitation to N2 fixation did not appear to be due to lower occupancy of nodules by Rhizobium strains with less potential for N2 fixation than those in limed soil. It is possible that the effect of acidity on NF influences DM, though sampling limitations made it difficult to generalize in this regard.

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