Subterranean clover mottle virus infection of subterranean clover: widespread occurrence in pastures and effects on productivity

1992 ◽  
Vol 43 (7) ◽  
pp. 1597 ◽  
Author(s):  
JM Wroth ◽  
RAC Jones
Keyword(s):  
Systemic Infection ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Seed Transmission ◽  
Dry Weight ◽  
Widespread Occurrence ◽  
Transmission Rates ◽  
Type Isolate ◽  
Growing Seasons ◽  
South West

In 1989 and 1990, infection with subterranean clover mottle sobemovirus (SCMV) was widespread in subterranean clover ( Trifolium subterraneum L.) pastures in the south-west of Western Australia. The virus was detected in 61% of the pastures sampled and incidences of infection ranged from 1 to 50%. The virus was more common in old pastures than in pastures resown with newer cultivars during the preceeding 5 year period. When 12 isolates of SCMV were inoculated to subterranean clover plants grown in the glasshouse, symptoms varied from mild to severe. SCMV isolates P23 and F4 decreased the herbage dry weight of cw. Daliak and Woogenellup grown in plots as spaced plants by 81-88% while the Type isolate caused losses of 92%. By contrast, losses were 37-49% with cv. Karridale, a cultivar in which systemic infection was either delayed or prevented during winter. Infection decreased seed yield by c. 90% in cvv. Karridale and Woogenellup with all three isolates; seed weight was decreased 21-55%. A small proportion of cv. Woogenellup transplants outgrew the infection in new shoots during late spring to produce abundant healthy foliage. SCMV seed transmission rates in seed collected from infected transplants of cv. Woogenellup were 0.06, 0.07 and 0.43% for the Type, P23 and F4 isolates respectively. It was concluded that SCMV was present in most pastures, but at low incidences, and that it persists in them from year to year. Extended growing seasons and hard grazing are likely to increase its incidence.

Occurrence of alfalfa mosaic and subterranean clover red leaf viruses in legume pastures in Western Australia

1995 ◽  
Vol 46 (4) ◽  
pp. 763 ◽  
Author(s):  
SJ McKirdy ◽  
RAC Jones
Keyword(s):  
Western Australia ◽  
Alfalfa Mosaic Virus ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Seed Transmission ◽  
Enzyme Linked Immunosorbent Assay ◽  
The South ◽  
Potential Threat ◽  
South West ◽  
Burr Medic

When leaf samples were collected from 94 Trifolium subterraneum (subterranean clover) pastures from six districts in spring 1993 in the south-west of Western Australia and tested by enzyme-linked immunosorbent assay, no alfalfa mosaic virus (AMV) or subterranean clover red leaf virus (SCRLV) was detected. In contrast, when 21 irrigated T. repens (white clover) pastures from one district (Bunbury) were sampled and tested in January (summer) 1994, AMV was detected in 16, with eight having infection levels >86%, while SCRLV was found in seven at infection levels of <12%. When a further five T. repens pastures were tested for AMV in October (spring) 1994, the virus was found in all with incidences up to 100%. None of the T. repens pastures with high levels of AMV infection had been resown with T. repens within the last 20 years, whereas those resown within the last five years had little or no infection. AMV was detected in 9/91 annual medic (Medicago spp.) pastures from seven wheatbelt districts sampled in spring 1991 or 1993; a single pasture of M. polymorpha (burr medic) cv. Serena was 21% infected, but the other eight infected ones had <3%. AMV seed transmission was detected in 1/19 commercial seed stocks of M. polymorpha harvested in 1991-93. AMV infection was followed over a 12-year period in M. murex (murex medic) cv. Zodiac seed stocks. It persisted readily through successive seed harvests during this period. It is concluded that infection with AMV and SCRLV is currently not a threat to T. subterraneum pastures in the south-west of Western Australia and that AMV seems not to be one in wheatbelt annual medic pastures provided these are sown with healthy medic seed. In contrast, AMV poses a potential threat to the productivity of irrigated T. repens pastures. SCRLV is also sometimes present in T. repens pastures, but was not found at serious levels.

Perennial and annual pasture species in the control of Silybum marianum

1968 ◽  
Vol 8 (30) ◽  
pp. 101 ◽  
Author(s):  
PW Michael
Keyword(s):  
New South ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Dry Weight ◽  
Silybum Marianum ◽  
South West ◽  
South Wales ◽  
Wimmera Ryegrass ◽  
Medicago Sativa L ◽  
Viable Seeds

Experiments begun in 1958 near Boorowa in the south-west slopes of New South Wales, have demonstrated the superiority of the perennials Hunter River lucerne (Medicago sativa L.) and Phalaris tuberosa L. over the annuals, Wimmera ryegrass (Lolium rigidum Gaud.) and subterranean clover (Trifolium subterraneum L.) in reducing establishment and growth of the annual thistle, Silybum marianum (L.) Gaertn. At one harvest (1959) the fresh weights of thistles varied from 0 in lucerne and 1 or 2 tons an acre in Phalaris to about 11 tons an acre in the annual plots. At another harvest (1960) the dry weight of thistles varied from about 0.2 cwt an acre in lucerne and Phalaris to about 5 cwt an acre in ryegrass plots. In the period of the experiment (mid 1958 to early 1967) there was an 85 per cent reduction in the numbers of apparently viable seeds of Silybum present in the soil of plots sown to lucerne and Phalaris.

Losses in herbage and seed yields caused by subterranean clover mottle sobemovirus in grazed subterranean clover swards

1995 ◽  
Vol 46 (4) ◽  
pp. 775 ◽  
Author(s):  
DG Ferris ◽  
RAC Jones
Keyword(s):  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Dry Weight ◽  
Virus Spread ◽  
Yield Losses ◽  
Growing Seasons ◽  
Heavy Grazing ◽  
Seed Yields ◽  
Weight Data ◽  
Different Levels

Subterranean clover (Trifolium subterraneum L.) was grown in swards into which small plants infected with subterranean clover mottle sobemovirus (SCMoV) were transplanted. Initial spread was mainly to plants adjacent to infected transplants and occurred during grazing and trampling by sheep. New sites of infection subsequently formed away from the original infection sites. Spread occurred mainly in spring and its extent varied with cultivar, site and year. Final SCMoV incidence in swards ranged from 17% of plants infected by isolate MJ in cv. Karridale in 1993 to 60% by isolate P23 in cv. Dinninup in 1991. With cvv. Dinninup and Junee, in two experiments SCMoV-infection decreased yields within patches with symptoms by 11-26% (herbage) and 5-31% (seed); in one of these experiments infection decreased overall yields of herbage by 9-10% and seed by 10-31%. In an experiment with cvv. Dalkeith and Woogenellup, SCMoV-induced overall herbage yield decreases of 10-13% were recorded despite extensive virus spread to control swards; yield losseswithin affected patches were 20-28% for herbage and 19% for seed. In an experiment with cw. Karridale and Woogenellup, SCMoV-induced yield losses within patches with symptoms were 38-44% for herbage and 15-41% for seed. Decreased seed size (mean seed weight) and fewer seeds both contributed to the diminished seed yields. Estimates of the effects of different levels of SCMoV infection on herbage yields were obtained for cv. Woogenellup by plotting dry weight data from (i) individual quadrats against percent plants with symptoms within them and (ii) whole plots against percent plot infection determined by ELISA. Losses increased in proportion to the level of infection. SCMoV infection of subterranean clover pastures not only decreases the feed available but also the seed bank which, when compounded over several years, leads to pasture deterioration. Heavy grazing, reseeding the pasture with susceptible cultivars and extended growing seasons are all likely to magnify SCMoV-induced losses.

The influence of seed size and depth of sowing on pre-emergence and early vegetative growth of subterranean clover (Trifolium subterraneum L.)

1956 ◽  
Vol 7 (2) ◽  
pp. 98 ◽  
Author(s):  
JN Black
Keyword(s):  
Leaf Area ◽  
Seed Size ◽  
Vegetative Growth ◽  
Dry Matter ◽  
Relative Rate ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Dry Weight ◽  
Total Leaf Area ◽  
Pot Culture

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.

Varietal reactions of Trifolium subterraneum L. to Phaseolus virus 2 Pierce.

1954 ◽  
Vol 5 (4) ◽  
pp. 598 ◽  
Author(s):  
EM Hutton ◽  
JW Peak
Keyword(s):  
Trypan Blue ◽  
Continuous Distribution ◽  
Systemic Infection ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Epidermal Cells ◽  
Severe Strain ◽  
Resistant Varieties ◽  
Lethal Reaction ◽  
The Mean

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.

Defoliation as a factor in the growth of varieties of subterranean clover (Trifolium subterraneum L) when grown in pure and mixed swards

1963 ◽  
Vol 14 (2) ◽  
pp. 206 ◽  
Author(s):  
JN Black
Keyword(s):  
Agricultural Research ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Dry Weight ◽  
Light Energy ◽  
Weight Changes ◽  
Agricultural Research Institute ◽  
Large Seed ◽  
Waite Agricultural Research Institute ◽  
High Yielding Varieties

This paper describes two experiments analysing the recovery from defoliation of subterranean clover varieties grown in swards in large seed boxes at the Waite Agricultural Research Institute, Adelaide. The first experiment examined the way in which the six common commercial varieties recovered from a single severe defoliation, and showed that under these conditions they can be placed in three groups: Yarloop and Clare are tall, high-yielding varieties with few, large leaves, recovering slowly from defoliation; Tallarook and Dwalganup are prostrate varieties, lower-yielding, with many small leaves, recovering rapidly after defoliation; Bacchus Marsh and Mount Barker are intermediate in all respects. In the second experiment mixed swards of equal numbers of Yarloop and Tallarook plants were grown under three treatments: A, no defoliation; B, defoliated twice at a height which removed the higher Yarloop canopy but left the lower Tallarook plants untouched; C, defoliated twice at a height which removed the canopies of both varieties. Measurement of dry weight on four occasions after each defoliation showed that in the undefoliated treatment, all Tallarook plants died by the end of the experiment. In the defoliated treatments, the removal of the Yarloop canopy resulted in only a temporary improvement in the illuniination in which the Tallarook plants grew, and their dry weight and plant numbers progressively declined. Dry weight changes in the Tallarook component were shown to be dependent on the light energy available to it, which was in turn determined by the light-absorbing capacity of the superior Yarloop canopy. In mixed swards, the ability of Yarloop to re-establish quickly a leaf canopy above that of Tallarook appeared to explain its success when defoliated.

The significance of petiole length, leaf area, and light interception in competition between strains of subterrranean clover (Trifolium subterraneum L.) grown in swards

1960 ◽  
Vol 11 (3) ◽  
pp. 277 ◽  
Author(s):  
JN Black
Keyword(s):  
Leaf Area ◽  
Leaf Development ◽  
Plant Competition ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Sampling Period ◽  
Dry Weight ◽  
Petiole Length ◽  
Petiole Elongation ◽  
Light Profiles

Three strains of subterranean clover differing in leaf development were grown in pure swards and in all combinations in mixtures. The strain Yarloop has relatively few large leaves held on long petioles; Tallarook has many small leaves and short petioles; Bacchus Marsh is intermediate in all these respects. The swards were grown in boxes and were sampled on four occasions during the period of vegetative growth. Leaf area in each 2 cm layer of the sward was determined separately, and for both strains in the mixed swards, and measurements of the light intensity reaching each layer were obtained. Root weights were determined for all swards and separately for each component of the mixed swards. Examination of the dry weights showed that the growth of the strain having the lesser petiole elongation was suppressed. In the extreme instance Tallarook was so suppressed when grown with Yarloop that in the final inter-sampling period it grew completely in the dark, and lost about half its dry weight. Bacchus Marsh also suppressed Tallarook, but to a lesser extent, while Bacchus Marsh was itself suppressed in competition with Yarloop. The amount of light energy intercepted by the two components of the mixed swards was calculated from the leaf area and light profiles, and confirmed the importance of the spatial distribution of leaves in plant competition. It was concluded that, in the absence of defoliation, the success of a strain under competition was associated with its potential petiole elongation.

Copper nutrition of subterranean clover (Trifolium subterraneum L. cv. Seaton Park). I. Effects of copper supply on growth and development

1981 ◽  
Vol 32 (2) ◽  
pp. 257 ◽  
Author(s):  
DJ Reuter ◽  
AD Robson ◽  
JF Loneragan ◽  
DJ Tranthim-Fryer
Keyword(s):  
Root Growth ◽  
Growth And Development ◽  
Copper Deficiency ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Dry Weight ◽  
Growing Season ◽  
Internode Elongation ◽  
Plant Parts ◽  
Lateral Branches

Effects of severe and moderate copper deficiency on the development of leaves and lateral branches, on the distribution of dry weight within the plant, and on seed yield of Seaton Park subterranean clover were assessed as part of three glasshouse experiments. Copper deficiency markedly depressed top and root growth without producing any distinctive symptoms. It retarded phasic development by delaying development of leaves and lateral branches, senescence of plant parts, and flowering: it also depressed the proportion of stem plus petiole in plant tops and decreased internode elongation, pollen fertility and the number of burrs and seeds formed. As a result of its effect in delaying flowering, copper deficiency would depress seed production particularly strongly when low soil water supply shortens the growing season. The need for suitable procedures for diagnosing copper deficiency is emphasized by the lack of specific plant symptoms in this species.

Zinc in subterranean clover (Trifolium subterraneum L. cv. Seaton Park). I. Effects of zinc supply on distribution of zinc and dry weight among plant parts

1982 ◽  
Vol 33 (6) ◽  
pp. 989 ◽  
Author(s):  
DJ Reuter ◽  
JF Loneragan ◽  
AD Robson ◽  
D Plaskett
Keyword(s):  
Zinc Deficiency ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Dry Weight ◽  
Physiological Age ◽  
Vegetative Development ◽  
Plant Parts ◽  
Zinc Concentrations ◽  
Complex Relationships ◽  
Lateral Branches

Effects of zinc supply on the distribution of zinc and dry weight among plant parts were examined during the first 55 days of vegetative development of Seaton Park subterranean clover grown in a zinc-deficient soil in a glasshouse. Symptoms of zinc deficiency first appeared in young trifoliate leaves. Zinc deficiency decreased the expansion of blades and petioles, delayed the development of leaves and lateral branches, depressed dry weights of roots and shoots, and increased the proportion of plant dry weight in roots and leaf blades. In each treatment and at each harvest, zinc concentrations varied widely amongst plant parts and with their physiological age. Plant parts also differed widely in the response of their dry matter and zinc concentrations to both zinc treatment and harvest time. It is suggested that these complex relationships explain why plant samples consisting of composite plant parts are not suitable for diagnosis of zinc deficiency. In the present experiment, zinc concentration in whole shoots was unsatisfactory for diagnosing zinc deficiency since concentrations were higher in young, zinc-deficient plants than in older, zinc-adequate plants. In young leaf blades of the same physiological age, zinc concentrations showed reasonably constant relationships with plant growth throughout the entire experiment. However, they varied two- to three-fold in leaves of different ages from the same plants. The results show the importance for diagnosis of zinc deficiency of selecting as a sample a single organ of defined physiological age. The youngest open leaf blade is recommended for diagnosis of zinc deficiency in subterranean clover.

Potential precision of the δ15N natural abundance method in field estimates of nitrogen fixation by crop and pasture legumes in south-west Australia

1994 ◽  
Vol 45 (1) ◽  
pp. 119 ◽  
Author(s):  
MJ Unkovich ◽  
JS Pate ◽  
P Sanford ◽  
EL Armstrong
Keyword(s):  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
B Value ◽  
Sampling Procedure ◽  
Natural Abundance ◽  
Incorrect Choice ◽  
Mass Spectrometric Measurement ◽  
B Values ◽  
South West ◽  
Reference Plant

Precision of estimation of the proportion of legume N derived from N2 fixation (%Ndfa) was assessed in relation to subterranean clover (Trifolium subterraneum L.) pastures and crops of pea (Pisum sativum L.) and lupin (Lupinus angustifolius L.) under south-west Australian conditions. By using a standardized 10-point sampling procedure of paired sampling of legume and reference plant and reference plant 15N natural abundance (S15N) values in the range from +2.9 to +4. 0%o, %Ndfa of sample crops of lupin and field pea and a clover pasture were assessed with respective precisions of 93� O.6%, 76� 2.4% and 91�1.3% (� s.e., n = 10). Effects on S15N due to isotope discrimination during fixation and subsequent distribution of N by the three study legumes were studied using sand-cultured, fully symbiotic plant material. The resulting S15N data (B values) showed consistently more negative values for shoots than roots (all species), no significant effects of cultivar on B values (all species), a marked effect of rhizobial strain on B value (subclover) and a tendency for B values to fall with plant age (pea and lupin). The likely magnitude of errors in %Ndfa estimates due to incorrect choice of B value was indicated. By using data for reference plant S15N values from field surveys and previously assessed error factors in mass spectrometric measurement of S15N, precision of estimation of %Ndfa by using bulked material from the 10-point field sampling procedure was predicted for situations ranging from where a legume was obtaining only minimal amounts (10%) through to the bulk (90%) of its N by atmospheric fixation.

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