Breakdown in resistance of subterranean clovers to clover scorch disease (Kabatiella caulivora)

1995 ◽  
Vol 46 (3) ◽  
pp. 645 ◽  
Author(s):  
MJ Barbetti
Keyword(s):  
Western Australia ◽  
Subterranean Clover ◽  
Improvement Program ◽  
Kabatiella Caulivora ◽  
New Race ◽  
Field Plots ◽  
Clover Scorch ◽  
Disease Testing

In spring 1990, in the Australasian Subterranean Clover and Alternative Legume Improvement Program field plots at Denmark, Western Australia, subterranean clover cultivars and crossbred lines normally highly resistant to clover scorch disease caused by Kabatiella caulivora, were severely affected by this disease. Testing the response of subterranean clover varieties to Kabatiella isolates taken from plants from these plots indicates the arrival of a new race of the fungus. The new race differs from all other isolates in overcoming the previously outstanding resistance of cultivars Green Range, Junee, Daliak and Esperance.

Resistance to clover scorch disease (Kabatiella caulivora) among accessions of purple clover (Trifolium purpureum) and its relationship to the eco-geography of collection sites

2010 ◽  
Vol 61 (1) ◽  
pp. 44 ◽  
Author(s):  
P. G. H. Nichols ◽  
R. Snowball ◽  
M. F. D'Antuono ◽  
M. J. Barbetti
Keyword(s):  
Mediterranean Basin ◽  
Subterranean Clover ◽  
Disease Reaction ◽  
Severity Scores ◽  
Kabatiella Caulivora ◽  
Field Plots ◽  
Disease Severity Scores ◽  
Clover Scorch ◽  
The Mediterranean Basin ◽  
Collection Sites

Visual ratings of disease reaction to a mixture of races 1 and 2 of clover scorch (Kabatiella caulivora) were conducted on inoculated field plots of 206 accessions of Trifolium purpureum (191 var. purpureum and 15 var. pamphyllicum) collected from the Mediterranean basin and surrounding regions. Disease severity scores of the resistant check, cv. Denmark subterranean clover (T. subterraneum), were clearly differentiated from the susceptible check, cv. Paratta purple clover. Nearly 33% of the accessions were resistant to both races. Resistant plants tended to flower later and originate from higher latitudes, where K. caulivora is more widespread. The results of this investigation led to development of ELECTRA™, the first cultivar of purple clover with resistance to both races of K. caulivora.

Resistance to race 1 of Kabatiella caulivora in subterranean clover (Trifolium subterraneum L.) cultivars and breeding lines

2008 ◽  
Vol 59 (6) ◽  
pp. 561 ◽  
Author(s):  
P. G. H. Nichols ◽  
M. P. You ◽  
M. J. Barbetti
Keyword(s):  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Breeding Lines ◽  
Race 1 ◽  
Kabatiella Caulivora ◽  
Selection For ◽  
Race 2 ◽  
Resistant Progeny ◽  
Clover Scorch

Twenty-eight cultivars and 106 F6-derived breeding lines of subterranean clover (Trifolium subterraneum) were screened in the field for their response to clover scorch disease caused by race 1 of Kabatiella caulivora. Eleven of the cultivars, including Denmark and Goulburn, were classified as resistant. Breeding lines with Denmark parentage had 55% of progeny with resistance, while those of Goulburn had only 19% of resistant progeny, suggesting different modes of inheritance. Selection for resistance to race 2 of K. caulivora in the F4 generation markedly increased the probability of selecting F6-derived lines with resistance to race 1, suggesting linkage between genes for resistance to both races.

Relations between stocking rate, environment and scorch disease on grazed subterranean clover pasture in Western Australia

1982 ◽  
Vol 22 (116) ◽  
pp. 182 ◽  
Author(s):  
WK Anderson ◽  
RJ Parkin ◽  
MD Dovey
Keyword(s):  
Western Australia ◽  
Chemical Control ◽  
Dry Matter ◽  
Disease Incidence ◽  
Subterranean Clover ◽  
Stocking Rate ◽  
Disease Symptoms ◽  
Sheep Production ◽  
Stocking Rates ◽  
Clover Scorch

The effects of weather on clover scorch disease caused by Kabatiella caulivora, the effects of the disease on pasture and sheep production, and the effect of sheep stocking rate (6, 8, 10 and 12 sheep/ha) on the disease were studied in a field experiment over three seasons near Albany, Western Australia. Spraying with benlate was used to control clover scorch on some treatments. Mean temperatures during the period when symptoms of the disease increased were in the range 11-17�C. Rainfall was frequent each year during the same period. The rapid increase in disease symptoms was observed when pasture dry matter on offer was approximately 2500 kg/ha. Disease symptoms decreased during a period of water stress of the pasture. Clover scorch disease had no consistent effect on pasture or animal production except that pasture dry matter on offer in spring was reduced in the unsprayed treatments at the lower stocking rates in the second two years. Higher stocking rates (10 and 12 sheep/ha) reduced the level of clover scorch symptoms without the use of chemical control with benlate. At the period of peak scorch symptoms a stocking rate of 10 sheep/ha reduced disease incidence by 20-35% compared with 6 sheep/ha in unsprayed plots. Increased sheep stocking rates are suggested as a possible alternative to chemical control or replacement of susceptible strains of subterranean clover in grazed pasture.

Variation in, and inheritance of seedling and adult-plant resistance in subterranean clover (Trifolium subterraneum L.) to leaf scorch (Kabatiella caulivora) (Kirch.) Karak

1990 ◽  
Vol 41 (1) ◽  
pp. 115 ◽  
Author(s):  
M Chandrashekar ◽  
GM Halloran
Keyword(s):  
Dominant Gene ◽  
Recessive Gene ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Single Recessive Gene ◽  
Seedling Resistance ◽  
Kabatiella Caulivora ◽  
The Cross ◽  
Clover Scorch ◽  
Adult Plants

The disease reaction of seedlings (2 weeks old) from a field collection of subterranean clover (Trifolium subterraneum) to clover scorch (Kabatiella caulivora (Kirch.) Karak), revealed 89 immune plants out of a total of 1530. However, with adult plants (15-16 weeks old) only one plant remained immune. In the F2 population of the cross of the cultivars (Daliak X Woogenellup (D X W), seedling resistance was conditioned by a single dominant gene and in the cross (Enfield X Woogenellup) (EX W) by a single recessive gene. However, with adult plants, resistance in the (D X W) F2 was conditioned by a single recessive gene and that in the (EX W) F2 by two recessive genes. The effect of increasing age in reducing the proportion of plants resistant to clover scorch in both studies indicates that caution is needed in evaluating resistance to clover scorch in epidemiological, breeding and genetic studies.

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.

Coolamon subterranean clover (Trifolium subterraneum L. var. subterraneum)

2007 ◽  
Vol 47 (2) ◽  
pp. 223 ◽  
Author(s):  
P. G. H. Nichols ◽  
M. J. Barbetti ◽  
G. A. Sandral ◽  
B. S. Dear ◽  
C. T. de Koning ◽  
...  
Keyword(s):  
New South ◽  
South Australia ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Growing Season ◽  
Improvement Program ◽  
Permanent Pasture ◽  
South Wales ◽  
Clover Scorch ◽  
Pasture Legume

Coolamon is a mid-season to late-season flowering F4-derived crossbred subterranean clover of var. subterraneum, developed by the collaborating organisations of the National Annual Pasture Legume Improvement Program. It is a replacement for Junee and has been selected for release on the basis of its greater herbage production and persistence, and its resistance to both known races of clover scorch. Coolamon is recommended for sowing in Western Australia, New South Wales, Victoria, South Australia and Queensland. It is best suited to well-drained, moderately acidic soils in areas with a growing season of 6.5–8 months that extends into November. Coolamon is best suited to phase farming and permanent pasture systems. It can also be used in cropping rotations, but at least 2 years of pasture are required between crops. Coolamon has been granted Plant Breeders Rights in Australia.

Differences in symptom development in subterranean clover infected with Kabatiella caulivora Race 1 and Race 2 are related to host resistance

2002 ◽  
Vol 53 (3) ◽  
pp. 305 ◽  
Author(s):  
K. L. Bayliss ◽  
J. Kuo ◽  
K. Sivasithamparam ◽  
M. J. Barbetti ◽  
E. S. Lagudah
Keyword(s):  
Subterranean Clover ◽  
Post Inoculation ◽  
Vascular Bundles ◽  
Incompatible Interaction ◽  
Mesophyll Cells ◽  
Starch Grains ◽  
Race 1 ◽  
Kabatiella Caulivora ◽  
Race 2 ◽  
Clover Scorch

Clover scorch (Kabatiella caulivora) is a severe fungal disease of Trifolium spp. contributing to the collapse of pasture swards across southern Australia during warm, humid spring weather. Host plant responses associated with resistance to the disease were determined in 2 cultivars of subterranean clover (T. subterraneum) separately inoculated with K. caulivora Race 1 or Race 2. Germination of conidia of both races reached a maximum 5 days post-inoculation on cv. Woogenellup (susceptible to both races) and 4 days post-inoculation on cv. Daliak (resistant to Race 1 but susceptible to Race 2). Germ tube growth of Race 1 was inhibited on cv. Daliak and the percentage of conidia penetrating leaf surfaces was lowest on this race–cultivar combination. Susceptibility was characterised by large petiole lesions, with invasive hyphae extending through the mesophyll tissue into the pith and then through the phloem tissue of vascular bundles, eventually causing the petioles to collapse. Resistance was characterised by small, black lesions with invasive hyphae extending no further than the fourth layer of mesophyll cells. A suberin-based material was observed beneath infected mesophyll cells in the incompatible interaction, beyond which no further growth of hyphae occurred. Race 2 caused a faster rate of host tissue necrosis than Race 1 and also the breakdown of starch grains in uninvaded petiole tissues. Starch grains in plants infected with Race 1 were evenly distributed in uninvaded tissue. Sporulation was rarely observed in the incompatible interaction but was common in compatible interactions within 15 days post-inoculation. These responses to K. caulivora can now be used as a breeding tool in evaluating and selecting improved resistance to clover scorch disease among breeding lines of subterranean clover.

Soil and tissue tests to predict pasture yield responses to applications of potassium fertiliser in high-rainfall areas of south-western Australia

2002 ◽  
Vol 42 (2) ◽  
pp. 149 ◽  
Author(s):  
M. D. A. Bolland ◽  
W. J. Cox ◽  
B. J. Codling
Keyword(s):  
Western Australia ◽  
Field Experiments ◽  
Relative Yield ◽  
Subterranean Clover ◽  
Test Method ◽  
Yield Response ◽  
Soil Test ◽  
Test Procedures ◽  
Pasture Production ◽  
Yield Responses

Dairy and beef pastures in the high (>800 mm annual average) rainfall areas of south-western Australia, based on subterranean clover (Trifolium subterraneum) and annual ryegrass (Lolium rigidum), grow on acidic to neutral deep (>40 cm) sands, up to 40 cm sand over loam or clay, or where loam or clay occur at the surface. Potassium deficiency is common, particularly for the sandy soils, requiring regular applications of fertiliser potassium for profitable pasture production. A large study was undertaken to assess 6 soil-test procedures, and tissue testing of dried herbage, as predictors of when fertiliser potassium was required for these pastures. The 100 field experiments, each conducted for 1 year, measured dried-herbage production separately for clover and ryegrass in response to applied fertiliser potassium (potassium chloride). Significant (P<0.05) increases in yield to applied potassium (yield response) were obtained in 42 experiments for clover and 6 experiments for ryegrass, indicating that grass roots were more able to access potassium from the soil than clover roots. When percentage of the maximum (relative) yield was related to soil-test potassium values for the top 10 cm of soil, the best relationships were obtained for the exchangeable (1 mol/L NH4Cl) and Colwell (0.5 mol/L NaHCO3-extracted) soil-test procedures for potassium. Both procedures accounted for about 42% of the variation for clover, 15% for ryegrass, and 32% for clover + grass. The Colwell procedure for the top 10 cm of soil is now the standard soil-test method for potassium used in Western Australia. No increases in clover yields to applied potassium were obtained for Colwell potassium at >100 mg/kg soil. There was always a clover-yield increase to applied potassium for Colwell potassium at <30 mg/kg soil. Corresponding potassium concentrations for ryegrass were >50 and <30 mg/kg soil. At potassium concentrations 30–100 mg/kg soil for clover and 30–50 mg/kg soil for ryegrass, the Colwell procedure did not reliably predict yield response, because from nil to large yield responses to applied potassium occurred. The Colwell procedure appears to extract the most labile potassium in the soil, including soluble potassium in soil solution and potassium balancing negative charge sites on soil constituents. In some soils, Colwell potassium was low indicating deficiency, yet plant roots may have accessed potassum deeper in the soil profile. Where the Colwell procedure does not reliably predict soil potassium status, tissue testing may help. The relationship between relative yield and tissue-test potassium varied markedly for different harvests in each year of the experiments, and for different experiments. For clover, the concentration of potassium in dried herbage that was related to 90% of the maximum, potassium non-limiting yield (critical potassium) was at the concentration of about 15 g/kg dried herbage for plants up to 8 weeks old, and at <10 g/kg dried herbage for plants older than 10–12 weeks. For ryegrass, there were insufficient data to provide reliable estimates of critical potassium.

The effects of different cultivars of subterranean clover (T. subterraneum L.) on sheep reproduction in the South-west of Western Australia

1970 ◽  
Vol 21 (2) ◽  
pp. 359 ◽  
Author(s):  
HL Davies ◽  
RC Rossiter ◽  
R Maller
Keyword(s):  
Western Australia ◽  
Uterine Prolapse ◽  
Subterranean Clover ◽  
Conception Rate ◽  
The South ◽  
Progressive Decline ◽  
South West ◽  
Conception Rates

The cultivars Dwalganup, Geraldton, Yarloop, Woogenellup, and Mt. Barker were each grazed continuously by Merino and Merino x Border Leicester ewes from April 1963 to November 1967. There was a progressive decline in the proportion of Merino ewes conceiving on the three high oestrogen cultivars Dwalganup, Geraldton, and Yarloop; crossbred ewes showed a decline on Dwalganup and Yarloop. For neither breed of sheep was the decline in conception rate significant on the two low oestrogen cultivars Woogenellup and Mt. Barker. The incidence of uterine prolapse was higher on the high oestrogen cultivars. The percentage lambs marked in 1967 was only 50% for the high oestrogen cultivars (excluding the crossbred ewes on Geraldton), compared with 93% for the low group. Conception rates were significantly related to the concentration of the isoflavone formononetin in the clover leaves.

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