Ecological studies of root-nodule bacteria introduced into field environments. II. Initial competition between seed inocula in the nodulation of Trifolium subterraneum L. seedlings

1968 ◽  
Vol 19 (5) ◽  
pp. 749 ◽  
Author(s):  
J Brockwell ◽  
WF Dudman
Keyword(s):  
Natural Population ◽  
Root Nodule ◽  
Field Experiments ◽  
Trifolium Subterraneum ◽  
Nodule Bacteria ◽  
Naturally Occurring ◽  
Diffusion Technique ◽  
Rhizobium Strains ◽  
Clover Seed ◽  
Legume Inoculants

The ability of three strains of Rhizobium trifolii used in legume inoculants to form nodules on inoculated Trifolium subterraneum L. was examined in field experiments on a soil containing a large natural population of clover rhizobia. The identity of cultures isolated from nodules on young seedlings was established by a gel immune diffusion technique. When a mixture of broth and peat inocula was applied to seed, a large proportion of nodules was attributable to peat-borne rhizobia. In competition with the natural population in the production of nodules on the roots of the host legume, strain WA67 = TA1 > UNZ29. In competition with each other as well as with the naturally occurring rhizobia, WA67 > TAI > UNZ29. The significance of the findings in relation to the persistence in soil of Rhizobium strains applied as inoculant to clover seed is discussed.

Corrigendum to: Boron deficiency in pasture based on subterranean clover (Trifolium subterraneum L.) is linked to symbiotic malfunction

2017 ◽  
Vol 68 (8) ◽  
pp. 805
Author(s):  
Leo J. Hamilton ◽  
Kevin F. M. Reed ◽  
Elainne M. A. Leach ◽  
John Brockwell
Keyword(s):  
N2 Fixation ◽  
Rhizobium Leguminosarum ◽  
Root Nodule ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Boron Deficiency ◽  
Nodule Bacteria ◽  
Clover Root ◽  
Per Se ◽  
Clover Seed

Field and glasshouse experiments confirmed the occurrence of boron (B) deficiency in subterranean clover (Trifolium subterraneum L.) pasture in eastern Victoria. Diminished productivity was linked to the small-seededness of clover and the poor effectiveness of clover root-nodule bacteria (rhizobia, Rhizobium leguminosarum bv. trifolii). Productivity, especially of clover and clover seed, increased following applications of up to 6 kg B ha–1 (P B deficiency in the nodulated legume induced conditions within the plant and or its rhizobia that led to impaired nitrogen (N2) fixation. Glasshouse research indicated that populations of soil-borne rhizobia taken from B-deficient soils were poorly effective in N2 fixation and that rhizobia from soils growing subterranean clover cv. Leura were significantly less effective (P Additionally, subterranean clover seed generated in B-deficient soils was at least one-third smaller than the seed of commercial seed but responded to inoculation with effective rhizobia. This indicated that any symbiotic malfunction of clover from B-deficient soils was not due to an inability to respond to nitrogen per se. On the other hand, cv. Leura from B-deficient soils fixed significantly less N2 than commercial cv. Leura when each was inoculated with rhizobia from B-deficient soils.

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.

Boron deficiency in pasture based on subterranean clover (Trifolium subterraneum L.) is linked to symbiotic malfunction

2015 ◽  
Vol 66 (11) ◽  
pp. 1197 ◽  
Author(s):  
Leo J. Hamilton ◽  
Kevin F. M. Reed ◽  
Elainne M. A. Leach ◽  
John Brockwell
Keyword(s):  
N2 Fixation ◽  
Rhizobium Leguminosarum ◽  
Root Nodule ◽  
Effective Strain ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Boron Deficiency ◽  
Initial Application ◽  
Clover Root ◽  
Clover Seed

Field and glasshouse experiments confirmed the occurrence of boron (B) deficiency in subterranean clover (Trifolium subterraneum L.) pasture in eastern Victoria. Diminished productivity was linked to the small-seededness of clover and the poor effectiveness of clover root-nodule bacteria (rhizobia, Rhizobium leguminosarum bv. trifolii). Productivity, especially of clover and clover seed, increased following applications of up to 6 kg B ha–1 (P < 0.001). The response was delayed, occurring several years after the initial application of B, unless the land was resown with fresh clover seed inoculated with an effective strain of rhizobia. B deficiency in the nodulated legume induced conditions within the plant and or its rhizobia that led to impaired nitrogen (N2) fixation. Glasshouse research indicated that populations of soil-borne rhizobia taken from B-deficient soils were poorly effective in N2 fixation and that rhizobia from soils growing subterranean clover cv. Leura were significantly less effective (P < 0.05) than rhizobia from a soil growing cv. Mt Barker. Additionally, subterranean clover seed generated in B-deficient soils was at least one-third smaller than the seed of commercial seed but responded to inoculation with effective rhizobia. This indicated that any symbiotic malfunction of clover from B-deficient soils was not due to an inability to respond to nitrogen per se. On the other hand, cv. Leura from B-deficient soils fixed significantly less N2 than commercial cv. Leura when each was inoculated with rhizobia from B-deficient soils.

Studies on nodulation responses to pelleting of subterranean clover seed.

1961 ◽  
Vol 12 (4) ◽  
pp. 578 ◽  
Author(s):  
JA Thompson
Keyword(s):  
Seed Coat ◽  
Field Experiments ◽  
Chemical Constituents ◽  
Chemical Properties ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Coating Materials ◽  
Physical Separation ◽  
Clover Seed

In a series of field experiments on seven soils of pH 6.0 or higher, nodulation of subterranean clover (Trifolium subterraneum L. var. Tallarook) was improved by pelleting the seed with various glues and coating materials, prior to inoculation with dry peat inoculum. On these soils the responses were not related to the chemical properties of the pellet materials. The beneficial effect was apparently the result of physical separation of the seed coat and inoculum. It is postulated that pelleting of seed protects the inoculum from an antibiotic, whlch has been found in subterranean clover seed coats, and which is active against Rhizobium in culture. On a soil of pH 5.1 a nodulation response to two types of pelleting materials was apparently related to the chemical constituents of the coating materials. In this soil there was less evidence of the importance of physical separation of the inoculum from the seed coat. It seems likely that soils may differ considerably in their ability to inactivate the antibiotic. Nodulation was not improved by in situ fumigation, prior to sowing, of two soils of pH 6.0 and 6.6, which indicated that antagonism by soil microorganisms was not the cause of poor nodulation in these soils. Significant nodulation responses to pelleting were obtained in sowings in these fumigated soils.

Genetic control of strain-specific ineffective nodulation in Trifolium subterraneum L.

1964 ◽  
Vol 15 (1) ◽  
pp. 37 ◽  
Author(s):  
AH Gibson
Keyword(s):  
Genetic Control ◽  
Bacterial Strain ◽  
Similar Pattern ◽  
Root Nodule ◽  
Major Gene ◽  
Trifolium Subterraneum ◽  
Nodule Bacteria ◽  
Root Nodule Bacteria ◽  
Parent Variety ◽  
Early Parent

The nodulation response of the Trifolium subterraneum variety Northam First Early with a range of strains of root nodule bacteria has been investigated. An ineffective response was found with the normally effective bacterial strain NA30. Within F2 populations of crosses between Northam First Early and each of six other varieties of T. subterraneum, the response to inoculation with strain NA30 varied from fully ineffective through intermediate effectiveness to fully effective. The proportion of ineffectively noddated plants in these F, populations was also influenced by the non- Northam First Early parent variety. Differences in response among individual plants within the F, populations were probably due to the segregation of a single major gene and a number of modifying genes. Of 10 other strains examined, one strain showed a similar pattern of response to that obtained with NA30, while a second strain exhibited host x strain specific ineffectiveness of a different type.

The phytotoxicity of the herbicides bromoxynil, pyridate, imazethapyr and a bromoxynil + diflufenican mixture on subterranean clover and lucerne seedlings

1999 ◽  
Vol 39 (7) ◽  
pp. 839 ◽  
Author(s):  
B. S. Dear ◽  
G. A. Sandral
Keyword(s):  
Soil Water ◽  
Seed Yield ◽  
Field Experiments ◽  
Seed Set ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Weed Suppression ◽  
Positive Effects ◽  
Clover Seed ◽  
High Level

Summary. The effect of the herbicides pyridate, imazethapyr and a bromoxynil + diflufenican mixture on subterranean clover (Trifolium subterraneum L.) (cvv. Trikkala and Karridale) and lucerne (Medicago sativa L.) (cv. Aurora) seedlings was examined in randomised plot field experiments in 2 successive years. Responses were compared against an unsprayed control and a standard bromoxynil application. The herbicides and the rates of product applied were: bromoxynil + diflufenican (0.5, 1.0 L/ha), imazethapyr (0.18, 0.3 L/ha), pyridate (1.0, 3.0 L/ha), and bromoxynil (1.4 L/ha). Weeds were removed by hand from the subterranean clover experiments but not the lucerne experiments. Pyridate and imazethapyr were the least phytotoxic of the herbicides applied on both subterranean clover and lucerne. The bromoxynil + diflufenican mixture was the most phytotoxic, causing severe leaf burn and a depression in herbage biomass in both species. Despite the high level of phytotoxicity by some treatments, none of the herbicides reduced lucerne seedling numbers. Lucerne herbage yields in late spring were higher in most sprayed plots compared with the unsprayed control due to the removal of weed competition. Seed yield responses in subterranean clover due to herbicide application ranged from negative responses up to –21% with pyridate to positive responses up to 92% with the bromoxynil + diflufenican treatment relative to the weed-free, unsprayed control. The positive responses were attributed to increased availability of soil water during seed set in treatments in which herbicides suppressed legume biomass. There was a good correlation in both 1992 (R2 = 0.85–0.89) and 1993 (R2 = 0.63–0.73) between the depression in herbage yield in spring and the increase in seed set relative to the control. Soil water under the subterranean clover cultivar Karridale in spring was highest in the bromoxynil and imazethapyr treatments, which produced a large reduction in biomass, and lowest in the control and pyridate treatments, which had showed the least depression in biomass 60 days after treatment application. Although some herbicides cause a high level of phytotoxicity, their use in weedy subterranean clover–lucerne mixtures is justified in view of the small negative, and potentially large positive, effects on subterranean clover seed yield and the increased lucerne yields later in the season due to weed suppression.

Ecological studies of root-nodule bacteria introduced into field environments. 4. Symbiotic properties of Rhizobium japonicum and competitive success in nodulation of two Glycine max cultivars by effective and ineffective strains

1976 ◽  
Vol 16 (81) ◽  
pp. 514 ◽  
Author(s):  
A Diatloff ◽  
J Brockwell
Keyword(s):  
Glycine Max ◽  
Root Nodule ◽  
Rhizobium Japonicum ◽  
Nodule Formation ◽  
Nodule Bacteria ◽  
Naturally Occurring ◽  
Competitive Success ◽  
Uninoculated Control ◽  
Strain Interaction ◽  
Symbiotic Properties

Rhizobium japonicum strain evaluation experiments with soybean (Glycine max) confirmed that strain CB1809 was ineffective in nitrogen fixation with the related cultivars Hardee and Geduld but was highly effective with cv. Hampton. There were no major symbiotic differences between the cultivars with other strains. Three strains including CB1809 were used, singly, in pairs, or all together, as inocula for Hardee and Hampton in competition studies in the field. The ratio of strains recovered from nodules was used as an index of competitive success. A few nodules contained more than one strain. There was a marked host x strain interaction in nodulating competitiveness related to symbiotic effectiveness, the order of competitive success being CB1809 > CC709 > CB1795 for Hampton and CC709 > CB1795 > CB1809 for Hardee. With Hardee, strain CB1809, although unsuccessful itself in forming nodules in the presence of the other inocula, appeared to suppress nodule formation by those strains. Nodulation by CB1795 in the presence of CB1809 was suppressed to such an extent that plant growth was retarded and not different from that of uninoculated control plants, although CB1795 alone nodulated Hardee abundantly and effectively. There was no evidence that naturally-occurring ineffective R. japonicum posed any competitive threat to the nodulating ability of effective inoculant strains.

Growth and survival of root-nodule bacteria in legume inoculants stored at high temperatures

1995 ◽  
Vol 27 (4-5) ◽  
pp. 707-712 ◽  
Author(s):  
R.J. Roughley ◽  
R.D.M. Simanungkalit ◽  
L.G. Gemell ◽  
E.J. Hartley ◽  
P. Cain
Keyword(s):  
High Temperatures ◽  
Root Nodule ◽  
Nodule Bacteria ◽  
Growth And Survival ◽  
Root Nodule Bacteria ◽  
Legume Inoculants

Ecological studies of root-nodule bacteria introduced into field environments. I. A survey of field performance of clover inoculants by gel immune diffusion serology

1968 ◽  
Vol 19 (5) ◽  
pp. 739 ◽  
Author(s):  
WF Dudman ◽  
J Brockwell
Keyword(s):  
Root Nodule ◽  
Natural Populations ◽  
Field Performance ◽  
The Other ◽  
Rhizobium Trifolii ◽  
Ecological Studies ◽  
Nodule Bacteria ◽  
Root Nodule Bacteria ◽  
Seed Inoculation ◽  
Clover Seed

A gel immune diffusion procedure for identifying strains of rhizobia has been used to follow the persistence of two strains of Rhizobium trifolii introduced simultaneously into soil by clover seed inoculation. Isolations of rhizobia were obtained from nodulated clover at intervals between 3 and 42 months after sowing. Of 456 isolates examined, 53.3% were recognized as inoculum strains but one strain, TA1, was recovered more than 11 times as frequently as the other, UNZ29. At one place, the inoculum was recovered 30 months after sowing but at another it had disappeared after 18 months. There was a significant trend for the proportion of recoverable inoculum strains to diminish with Iapse of time between sowing and isolation. Even in places where natural populations of Rh. Trifolii were small or undetectable, there was no evidence to suggest that the strains introduced as seed inoculant were likely to become permanently established as a large proportion of the nodule bacteria in the soil.

scholarly journals Evaluating the Impact of Two Generalist Predators on the Leafhopper Erasmoneura vulnerata Population Density

Insects ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 321
Author(s):  
Stefan Cristian Prazaru ◽  
Giulia Zanettin ◽  
Alberto Pozzebon ◽  
Paola Tirello ◽  
Francesco Toffoletto ◽  
...  
Keyword(s):  
Field Experiments ◽  
Field Studies ◽  
Generalist Predators ◽  
Predator Species ◽  
Potted Plants ◽  
Naturally Occurring ◽  
Orius Majusculus ◽  
Limited Effectiveness ◽  
Pest Outbreaks ◽  
The Impact

Outbreaks of the Nearctic leafhopper Erasmoneura vulnerata represent a threat to vinegrowers in Southern Europe, in particular in North-eastern Italy. The pest outbreaks are frequent in organic vineyards because insecticides labeled for organic viticulture show limited effectiveness towards leafhoppers. On the other hand, the naturally occurring predators and parasitoids of E. vulnerata in vineyards are often not able to keep leafhopper densities at acceptable levels for vine-growers. In this study, we evaluated the potential of two generalist, commercially available predators, Chrysoperla carnea and Orius majusculus, in suppressing E. vulnerata. Laboratory and semi-field experiments were carried out to evaluate both species’ predation capacity on E. vulnerata nymphs. The experiments were conducted on grapevine leaves inside Petri dishes (laboratory) and on potted and caged grapevines (semi-field); in both experiments, the leaves or potted plants were infested with E. vulnerata nymphs prior to predator releases. Both predator species exhibited a remarkable voracity and significantly reduced leafhopper densities in laboratory and semi-field experiments. Therefore, field studies were carried out over two growing seasons in two vineyards. We released 4 O. majusculus adults and 30 C. carnea larvae per m2 of canopy. Predator releases in vineyards reduced leafhopper densities by about 30% compared to the control plots. Results obtained in this study showed that the two predators have a potential to suppress the pest density, but more research is required to define appropriate predator–prey release ratios and release timing. Studies on intraguild interactions and competition with naturally occurring predators are also suggested.

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