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.

Effect of reference plant on estimation of nitrogen fixation by subterranean clover using 15N methods

1985 ◽  
Vol 36 (5) ◽  
pp. 663 ◽  
Author(s):  
SF Ledgard ◽  
JR Simpson ◽  
JR Freney ◽  
FJ Bergersen
Keyword(s):  
Isotope Dilution ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
15N Isotope Dilution ◽  
Soil N ◽  
15N Isotope ◽  
Reference Plant ◽  
Reconstituted Soil ◽  
Isotope Technique ◽  
Indigenous Plant

Subterranean clover (Trifolium subterraneum L.) was grown in separate associations with annual ryegrass (Lolium rigidum Gaud.) and with phalaris (Phalaris aguatica L.) in reconstituted soil profiles (0-400 mm depth), and N2 fixation was measured by 15N isotope dilution and 15N natural abundance methods. In all experiments, two values were determined, viz. P, the percentage of clover nitrogen (N) iixed from atmospheric N2, and R, the ratio of N assimilated from added 15N-labelled N to N assimilated from indigenous soil N. Estimates of P that were negative were obtained for the clover/phalaris association, using 15N isotope dilution, during the first 16 days after 15N addition. This was due to the R value being higher for clover than for phalaris, which in turn was due to differences in their temporal pattern of growth interacting with a declining ISN enrichment of the plant-available soil N. The R values for clover and ryegrass, when grown together, were similar throughout the experiment, and estimates of P by 15N isotope dilution and natural 15N abundance were similar. The activity of plant roots in different soil layers was examined by injecting a solution of 15N-labelled nitrate at 50, 150 and 300 mm depths. Uptake of 15N was similar at all depths for phalaris and clover, whereas ryegrass assimilated a greater amount at 150 and 300 mrn. However, since the amounts of roots and indigenous plant-available soil N were small in the 100-400 mm zone relative to the 0-100 mm zone, the greater activity of ryegrass roots at depth had no significant effect on the estimates of P. In both plant associations, the estimates of P, by both of the 15N methods, increased with time, and were higher in the clover/ryegrass association than with clover/phalaris. Since this was associated with lower levels of inorganic soil N in the clover/ryegrass association, it must be recognized that the reference plant can induce real changes in P by influencing the soil N status, in the association, as well as causing erroneous estimates of P by the 15N isotope technique.

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.

Taxonomic and pathogenic characteristics of a new species Aphanomyces trifolii causing root rot of subterranean clover (Trifolium subterraneum) in Western Australia

2010 ◽  
Vol 61 (9) ◽  
pp. 708 ◽  
Author(s):  
Tiernan A. O'Rourke ◽  
Megan H. Ryan ◽  
Hua Li ◽  
Xuanli Ma ◽  
Krishnapillai Sivasithamparam ◽  
...  
Keyword(s):  
New Species ◽  
Western Australia ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Root Disease ◽  
Molecular Characteristics ◽  
Root Pruning ◽  
High Rainfall ◽  
South West ◽  
A New Species

Subterranean clover (Trifolium subterraneum) is grown extensively as a pasture legume in agronomic regions with Mediterranean-type climates in parts of Africa, Asia, Australia, Europe, North America and South America. Root diseases of subterranean clover, especially those caused by oomycete pathogens including Aphanomyces, Phytophthora and Pythium, greatly reduce productivity by significantly decreasing germination, seedling establishment, plant survival and seed set. For this reason, experiments were conducted to determine the species of Aphanomyces causing root disease on subterranean clover in the high-rainfall areas of south-west Western Australia. The effects of flooding, temperature and inoculum concentration on the development of root disease on subterranean clover caused by this Aphanomyces sp. were also investigated as was its host range. Morphological and molecular characteristics were used to identify the pathogen as a new species Aphanomyces trifolii sp. nov. (O’Rourke et al.), which forms a distinct clade with its nearest relative being A. cladogamus. A. trifolii caused significant lateral root pruning as well as hypocotyl collapse and tap root disease of subterranean clover. The level of disease was greater in treatments where soil was flooded for 24 h rather than for 6 h or in unflooded treatments. The pathogen caused more disease at 18/13oC than at lower (10/5oC) or higher (25/20oC) temperatures. The pathogen caused more disease at 1% inoculum than at 0.5 or 0.2% (% inoculum : dry weight of soil). In greenhouse trials, A. trifolii also caused root disease on annual medic (M. polymorpha and M. truncatula), dwarf beans (Phaseolus vulgaris) and tomatoes (Solanum lycopersicum). However, the pathogen did not cause disease on peas (Pisum sativum), chickpea (Cicer arietinum), wheat (Triticum aestivum), annual ryegrass (Lolium rigidium) or capsicum (Capsicum annuum). A. trifolii is a serious pathogen in the high-rainfall areas of south-west Western Australia and is likely a significant cause of root disease and subsequent decline in subterranean clover pastures across southern Australia.

Breeding and farming system opportunities for pasture legumes facing increasing climate variability in the south-west of Western Australia

2012 ◽  
Vol 63 (9) ◽  
pp. 840 ◽  
Author(s):  
C. K. Revell ◽  
M. A. Ewing ◽  
B. J. Nutt
Keyword(s):  
Western Australia ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Farming System ◽  
Annual Rainfall ◽  
The South ◽  
Pasture Legumes ◽  
South West ◽  
Annual Medics ◽  
Phosphorus And Potassium

The south-west of Western Australia has experienced a declining trend in annual rainfall and gradual warming over the last 30 years. The distribution of rainfall has also changed, with lower autumn rainfall, patchy breaks to the season, and shorter springs. This has important implications for the productivity of legume pastures in the region, which is dominated by annual species, particularly subterranean clover (Trifolium subterraneum L.), annual medics (Medicago spp.), serradella (Ornithopus spp.), and biserrula (Biserrula pelecinus L.). For annual pasture legumes, appropriate patterns of seed softening and germination behaviour, efficiency of phosphorus and potassium uptake, responses to elevated levels of atmospheric CO2, and drought resistance of seedlings and mature plants will assume increasing importance. While these traits can be targeted in pasture breeding programs, it will also be important to exploit farming system opportunities to optimise the annual legume component of the feed base. These opportunities may take the form of incorporating strategic shrub reserves and grazing crops to allow for pasture deferment in autumn–winter. Perennial forages may become more important in this context, as discussed in terms of the development of the perennial legume tedera (Bituminaria bituminosa var. albomarginata C.H. Stirton).

Selection of reference plants for 15N natural abundance assessment of N2 fixation by crop and pasture legumes in south-west Australia

1994 ◽  
Vol 45 (1) ◽  
pp. 133 ◽  
Author(s):  
JS Pate ◽  
MJ Unkovich ◽  
EL Armstrong ◽  
P Sanford
Keyword(s):  
N2 Fixation ◽  
Subterranean Clover ◽  
15N Natural Abundance ◽  
Natural Abundance ◽  
Field Pea ◽  
Legume Species ◽  
Reference Species ◽  
Rooting Zone ◽  
South West ◽  
Reference Plants

The 15N natural abundance (S15N) of the shoot total N of a range of non-N2 fixing potential reference species was compared with that of nodulated field pea (Pisum sativum L.), narrow leafed lupin (Lupinus angustijolius L.) or subterranean clover (Trijolium subterraneum L.) across a range of field sites, to which N fertilizers had not been applied in the season of study. Shoot S15N values of reference species lay mostly within the range from +3 to +5%o and there was some evidence of lower S15N values in gramineaceous than dicotyledonous non-legume species. Continuous sampling within crops of each legume showed S15N values to differ consistently between and within potential reference species through the season. The S15N values of seedlings of four non legume species in a lupin crop were closer to that of soil N03-N (S15N = 4.2%o) than soil NH4-N (S15N = 7.9%0). Shoot S15N values of non-nodulated pea, lupin and subterranean clover, and a range of possible reference species all sand-cultured on a defined nitrate source (S15N = 7.5%), suggested little or no discrimination during utilization of nitrate. However, when four candidate reference species were sand cultured with nodulated actively fixing subterranean clover on the same nitrate source, the S15N of the ryegrass was lowered significantly below that of the NO3. Field plot comparisons of nine potential reference species with nodulated field pea showed certain species to resemble field pea more closely than others in terms of the S15N value of their shoots. Reference plants sampled within or well outside the rooting zone of an actively fixing legume (subterranean clover, field pea or lupin) showed significantly lower shoot S15N of mixed grass components when harvested in root contact with, as opposed to well distant from, subterranean clover. A similar effect was observed for barley within v. outside the rooting zone of pea, but no such effects were observed between capeweed and subterranean clover, pea and radish, or for any of five reference plants matched with lupin. The data are utilized to select appropriate reference plants for field assessments of N2 fixation under south-west Australian conditions.

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.

Sources of variation in the resistance of subterranean clover to clover scorch (Kabatiella caulivora) in the field

1975 ◽  
Vol 15 (75) ◽  
pp. 541 ◽  
Author(s):  
DL Chatel ◽  
CM Francis
Keyword(s):  
Regression Analysis ◽  
Multiple Regression Analysis ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
North African ◽  
Test Conditions ◽  
South West ◽  
Sources Of Variation ◽  
Kabatiella Caulivora ◽  
Clover Scorch

The resistance of 307 varieties of subterranean clover (Trifolium subterraneum) to the clover scorch disease pathogen was assessed in three locations in south west Australia. Disease intensity as measured by visual ratings of sward damage was found to vary with variety and location. Resistance was independent of subspecies groupings but dependent on country of origin. Spanish and Portugese varieties were generally less susceptible than North African selections. Disease severity was also related to plant characters by correlation and multiple regression analysis. Late maturing varieties were most resistant under the test conditions and rapidly growing earlier varieties, with large pale leaves and thick petioles, were least resistant.

Occurrence of bean yellow mosaic virus in subterranean clover pastures and perennial native legumes

1994 ◽  
Vol 45 (1) ◽  
pp. 183 ◽  
Author(s):  
SJ McKirdy ◽  
BA Coutts ◽  
RAC Jones
Keyword(s):  
Mosaic Virus ◽  
Western Australia ◽  
White Clover ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Bean Yellow Mosaic Virus ◽  
Yellow Vein ◽  
Yellow Mosaic Virus ◽  
South West ◽  
Clover Yellow Vein Virus

In 1990, infection with bean yellow mosaic virus (BYMV) was widespread in subterranean clover (Trifolium subterraneum) pastures in the south-west of Western Australia. When 100 leaves were sampled at random per pasture, the virus was detected by ELISA in 23 of 87 pastures and incidences of infection ranged from 1 to 64%. BYMV was present in all seven districts surveyed, but highest incidences of infection occurred in the Busselton district. In smaller surveys in 1989 and 1992, incidences of infection in pastures were higher than in 1990, and ranged up to 90%. In 1992, when petals from 1703 samples of 59 species of perennial native legumes from 117 sites were tested by ELISA, only 1% were found infected with BYMV. The infected samples came from 5/7 districts surveyed. Species found infected were Kennedia prostrata, K. coccinea, Hovea elliptica and H. pungens. Representative isolates of BYMV from subterranean clover and native legumes did not infect white clover systemically confirming that clover yellow vein virus (CYVV) was not involved. It was concluded that BYMV infection was present in many subterranean clover pastures, but normally at low incidences, except in epidemic years such as 1992. Also, perennial native legumes are unlikely to act as major reservoirs for reinfection of annual pastures each year. In areas of Australia with Mediterranean climates where perennial pastures are absent, persistence of the virus over summer is therefore by some other method than infection of perennials.

Studies on the nutrition of pasture plants in the South-west of Western Australia. III. The effect of sulphur on the growth of subterranean clover (Trifolium subterraneum L.)

1952 ◽  
Vol 3 (1) ◽  
pp. 7 ◽  
Author(s):  
RC Rossiter
Keyword(s):  
Field Trial ◽  
Sandy Soils ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Calcium Sulphate ◽  
Sodium Sulphate ◽  
Deficiency Symptoms ◽  
South West ◽  
Pasture Plants ◽  
Pot Culture

Sulphur applied as calcium sulphate or sodium sulphate significantly increased the growth of subterranean clover on a number of sandy soils in pot culture and also on a gravelly sand under field conditions at Kojonup. In the field trial a significant response was also obtained in the volunteer annual, capeweed.Total sulphur in the tops of both clover and capeweed was markedly increased by sulphur application; the lowest values were observed in one of the pot-culture trials, where deficiency symptoms were most prominent. Some reasons are suggested for the earlier appearance of deficiency symptoms in the field trial, where the deficiency was less severe than in the pot-culture experiments.

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.

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