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

1961 ◽  
Vol 12 (2) ◽  
pp. 212 ◽  
Author(s):  
PS Nutman

(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.

1960 ◽  
Vol 13 (4) ◽  
pp. 456 ◽  
Author(s):  
NP Kefford ◽  
J Brockwell ◽  
JA Zwar

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.


1964 ◽  
Vol 15 (1) ◽  
pp. 37 ◽  
Author(s):  
AH Gibson

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.


1968 ◽  
Vol 19 (6) ◽  
pp. 891 ◽  
Author(s):  
AH Gibson ◽  
J Brockwell

An examination was made of the ability of lines of Trifolium subterraneum L. subsp. subterraneum, subsp. yanninicum Katzn. et Morley, and subsp. brachycalycinum Katzn. et Morley to nodulate and fix nitrogen with strains of .Rlzizobium trifolii isolated from habitats dominated by each of the subspecies.Host line x bacterial strain specificity was demonstrated at two levels: (a) some strains nodulated one, or two, host lines ineffectively, yet formed an effective symbiosis with the other host lines; (b) among the symbiotic combinations classed as effective, the degree of effectiveness of the strains was dependent on the host lines. It was found that the lines of a subspecies were not more effectively nodulated by the bacterial strains isolated from a habitat in which that subspecies was the predominant subterranean clover, than they were by strains isolated from habitats in which the other subspecies predominated. For example, lines of T. subterraneum subsp. yanninicum fixed nitrogen as well with strains of R. trifolii isolated from habitats of subsp. subterraneum or subsp. brachycalycinum as they did with strains isolated from its own habitat. Similarly, there was little evidence that the strains from the habitat in which a subspecies predominated were more effective in their symbiosis with the lines of that subspecies than they were with the lines of the other subspecies. The only exception to this latter generalization was that the strains isolated from the subsp. brachycalycinum habitat were slightly more effective with subsp. brachycalycinum than with subspp. yanninicum or subterraneum. Groupings of the strains based on their response with the lines of any subspecies, or with the lines of all subspecies combined, bore no relation to groupings based on the origin of the strains. It was concluded that it was not possible to predict the effectiveness of any symbiotic combination from a consideration of the taxonomy of the host or the habitat from which the bacterium was isolated. The feasibility of using a standard host line for the screening of the general effectiveness of all strains of potential value in subterranean clover inoculants is discussed. The commercial inoculant strain, TA1, was not the most effective strain with all lines, and overall, ranked fifth among the strains examined.


2017 ◽  
Vol 68 (8) ◽  
pp. 805
Author(s):  
Leo J. Hamilton ◽  
Kevin F. M. Reed ◽  
Elainne M. A. Leach ◽  
John Brockwell

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.


1969 ◽  
Vol 172 (1029) ◽  
pp. 417-437 ◽  

Soon after the isolation of nodule bacteria in 1888, differences were recognized in the ability of bacterial strains to form nodules on particular host plants and in the nitrogen-fixing ability of the nodules so formed. These and other symbiotic heterogeneities were attributed, sometimes correctly, to bacterial strain differences, not then thought to be open to formal genetic analysis. The realization that the host plant was an essential component of this variability came only gradually, stimulated by observations of host varietal differences and by the demand for reliable and homogeneous material for experimental work. Only within the last two decades has host variability been studied by plant breeding, and bacterial strain differences by some of the methods of microbial genetics. This review, except for a brief reference to earlier work of some historic interest, will consider only genetic problems open to investigation by these methods. The developmental sequence in all legume nodules is broadly similar. The initial infection phases are followed by the induction of the nodule, the invasion of part of the nodular tissue and culminate in bacteroid formation and nitrogen fixation; the genetics of symbiosis will be considered in this context.


2000 ◽  
Vol 51 (3) ◽  
pp. 377 ◽  
Author(s):  
G. M. Lodge

Seedlings of 3 perennial grasses, Danthonia linkii Kunthcv. Bunderra, D. richardsonii Cashmore cv. Taranna(wallaby grasses), and Phalaris aquatica L. cv. Sirosa,were each grown in replacement series mixtures with seedlings ofTrifolium repens L. (white clover),Trifolium subterraneum L. var. brachycalycinum (Katzn.et Morley) Zorahy & Heller cv. Clare (subterraneanclover), and Lolium rigidum L. (annual ryegrass). Plantswere sown 5 cm apart in boxes (45 by 29 by 20 cm) at a density of 307plants/m2. Maximum likelihood estimates were usedto derive parameters of a non-linear competition model using the dry matterweights of perennial grasses and competitors at 3 harvests, approximately 168,216, and 271 days after sowing. Intra-plant competition was examined inmonocultures of each species, grown at plant spacings of 2, 5, and 8 cm apartwith plants harvested at the above times.Competition occurred in all perennial grass–competitor mixtures, exceptin those of each perennial grass with white clover and thephalaris–subterranean clover mixture (Harvest 1) and those withD. richardsonii and phalaris grown with white clover(Harvest 2). For D. richardsonii (Harvests 1 and 2) andD. linkii (Harvest 1 only) grown with white clover andthe phalaris–subterranean clover (Harvest 1), the two species in themixture were not competing. In the phalaris–white clover mixture, eachspecies was equally competitive (Harvests 1 and 2). These differences incompetition and aggressiveness reflected differences in individual plantweights in monocultures where there was an effect (P < 0.05) of species ondry matter weight per box, but no significant effect of plant spacing.These data indicated that for successful establishment,D. richardsonii and D. linkiishould not be sown in swards with either subterranean clover or white clover,or where populations of annual ryegrass seedlings are likely to be high.Phalaris was more compatible with both white clover and subterranean clover,but aggressively competed with by annual ryegrass.


2004 ◽  
Vol 94 (5) ◽  
pp. 433-439 ◽  
Author(s):  
S.N. Johnson ◽  
P.J. Gregory ◽  
P.J. Murray ◽  
X Zhang ◽  
I.M. Young

AbstractThis study investigated the ability of neonatal larvae of the root-feeding weevil, Sitona lepidus Gyllenhal, to locate white clover Trifolium repens L. (Fabaceae) roots growing in soil and to distinguish them from the roots of other species of clover and a co-occurring grass species. Choice experiments used a combination of invasive techniques and the novel technique of high resolution X-ray microtomography to non-invasively track larval movement in the soil towards plant roots. Burrowing distances towards roots of different plant species were also examined. Newly hatched S. lepidus recognized T. repens roots and moved preferentially towards them when given a choice of roots of subterranean clover, Trifolium subterraneum L. (Fabaceae), strawberry clover Trifolium fragiferum L. (Fabaceae), or perennial ryegrass Lolium perenneL. (Poaceae). Larvae recognized T. repens roots, whether released in groups of five or singly, when released 25 mm (meso-scale recognition) or 60 mm (macro-scale recognition) away from plant roots. There was no statistically significant difference in movement rates of larvae.


1956 ◽  
Vol 7 (2) ◽  
pp. 98 ◽  
Author(s):  
JN Black

Changes in the pre-emergence distribution of dry matter in subterranean clover (Trifolium subterraneum L.) variety Bacchus Marsh were followed at 21°C, using three sizes of seed and three depths of sowing, ½, 1¼, and 2 in. Decreasing seed size and increasing depth of sowing both reduce the weight of the cotyledons a t emergence. Seed of the three sizes were sown a t three depths in pot culture a t staggered intervals so that emergence was simultaneous. Dry weight in the early vegetative stage was proportional to seed size, and total leaf area and leaf numbers showed similar trends. Plants of each seed size grew at the same relative rate. No effect of depth of sowing could be detected, and this was shown to be due to the cotyledon area a t emergence being constant for any given seed size, regardless of varying depth of sowing and hence of cotyledon weight. It was concluded that seed size in a plant having epigeal germination and without endosperm is of importance: firstly, in limiting the maximum hypocotyl elongation and hence depth of sowing, and secondly, in determining cotyledon area. Cotyledon area in turn influences seedling growth, which is not affected by cotyledon weight. Once emergence has taken place, cotyledonary reserves are of no further significance in the growth of the plants.


Author(s):  
H. Neave ◽  
C.H. Hewlett

The information contained in this paper is principally first-hand knowledge extending over a period of six years gained from personal experience from our own "Oakleigh" farm.


1954 ◽  
Vol 5 (4) ◽  
pp. 598 ◽  
Author(s):  
EM Hutton ◽  
JW Peak

A number of varieties of subterranean clover (Trifolium subterraneum L.) were tested with a severe strain of Phaseolus virus 2 Pierce. Northam First Early, Dwalganup, and Pink Flowered gave lethal necrotic reactions while the rest developed mottles and chlorosis of different degrees of intensity. Reductions in the mean fresh weights of plants of five subterranean clover varieties ranged from 26.1 to 76.7 per cent. Epidermal cells of mottled leaves contained irregular aggregates of viroplasts stained by treatment with phloxine-trypan blue. Viroplasts in young tip leaves did not stain if the plants were held at temperatures below 44.6°F while those in mature basal leaves were not so affected. The lethal-reactors Northam First Early, Dwalganup, and Pink Flowered were resistant in the field to Phaseolus virus 2. With hand inoculation in the glass-house an average of 10 per cent. of plants of these varieties remained free from systemic infection, whereas all the plants of mottle-reacting varieties became systemically infected. The virus had a discontinous distribution in plants of lethal-reactors, compared with a continuous distribution in those of mottle-reactors such as Mount Barker. The lethal reaction is heritable in a dominant fashion in most crosses, so that the development of desirable new virus- resistant varieties is possible.


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