Natural resistance to bean yellow mosaic potyvirus in subterranean clover

1996 ◽  
Vol 47 (4) ◽  
pp. 605 ◽  
Author(s):  
DG Ferris ◽  
RAC Jones
Keyword(s):  
Field Experiments ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Hypersensitive Reaction ◽  
Natural Resistance ◽  
Yellow Mosaic Virus ◽  
Physiological Age ◽  
Hypersensitive Resistance ◽  
Breeding Programs ◽  
Mature Plant Resistance

Seed of 31 named cultivars and 11 other genotypes of Trifolium subterraneum (subterranean clover) was sown in 3 major and 3 smaller scale field experiments. In these, bean yellow mosaic virus (BYMV) was spread from infector plants to test rows by naturally occurring aphids. The numbers of clover plants developing BYMV symptoms in each row were counted at different times. Based on the results from at least 2 field experiments, different genotypes were assigned to 1 of 5 BYMV infection categories (A-E), ranging from greatest (A) to least (E) infection. Category A was found to contain genotypes that were latest maturing while, except for cv. Rosedale (ssp. brachycalycinum) which was in E despite being of intermediate maturity, category E contained earliest maturing genotypes. Except for cv. Rosedale, when the percentages of plants with BYMV symptoms in the 3 main experiments were plotted against days to flowering previously established for each genotype, the two were closely related. However, when young plants of cultivars in categories D or E were aphid-inoculated with 2 BYMV isolates, they became infected to a similar extent to young plants of 2 late-maturing cultivars from category A. This suggests that, except for cv. Rosedale, the extent of BYMV infection obtained in the field was determined by plant physiological age, plants of late-maturing genotypes being easier for viruliferous aphids to infect with BYMV than plants of early-maturing genotypes of the same age but physiologically older, a phenomenon known as 'mature plant resistance'. When plants of cv. Rosedale were aphid-inoculated with 7 different isolates of BYMV, a systemic hypersensitive reaction developed with 5 isolates but not with two others. This suggests that cv. Rosedale has 'strain specific hypersensitive resistance' to BYMV. No systemic hypersensitive reaction developed when the same 7 BYMV isolates were aphid-inoculated to cv. Dwalganup and named selections Pink Flowered and Northam Early, genotypes previously reported to react hypersensitively to potyvirus infection. The field screening procedure employed is suitable for use by T. subterraneum breeding programs seeking to develop new cultivars with resistance to BYMV. Cultivar Rosedale may prove a suitable source of resistance to use as a parent in crossing programs aimed at producing cultivars with natural BYMV resistance.

Comparing different sources of sulfur for high-rainfall pastures insouth-western Australia

2003 ◽  
Vol 43 (10) ◽  
pp. 1221 ◽  
Author(s):  
M. D. A. Bolland ◽  
J. S. Yeates ◽  
M. F. Clarke
Keyword(s):  
Western Australia ◽  
Field Experiments ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Residual Value ◽  
Single Superphosphate ◽  
Pasture Production ◽  
Leaching Losses ◽  
S Deficiency ◽  
Different Sources

The dry herbage yield increase (response) of subterranean clover (Trifolium subterraneum L.)-based pasture (>85% clover) to applications of different sources of sulfur (S) was compared in 7 field experiments on very sandy soils in the > 650 mm annual average rainfall areas of south-western Australia where S deficiency of clover is common when pastures grow rapidly during spring (August–November). The sources compared were single superphosphate, finely grained and coarsely grained gypsum from deposits in south-western Australia, and elemental S. All sources were broadcast (topdressed) once only onto each plot, 3 weeks after pasture emerged at the start of the first growing season. In each subsequent year, fresh fertiliser-S as single superphosphate was applied 3 weeks after pasture emerged to nil-S plots previously not treated with S since the start of the experiment. This was to determine the residual value of sources applied at the start of the experiment in each subsequent year relative to superphosphate freshly-applied in each subsequent year. In addition, superphosphate was also applied 6, 12 and 16 weeks after emergence of pasture in each year, using nil-S plots not previously treated with S since the start of the experiment. Pasture responses to applied S are usually larger after mid-August, so applying S later may match plant demand increasing the effectiveness of S for pasture production and may also reduce leaching losses of the applied S.At the same site, yield increases to applied S varied greatly, from 0 to 300%, at different harvests in the same or different years. These variations in yield responses to applied S are attributed to the net effect of mineralisation of different amounts of S from soil organic matter, dissolution of S from fertilisers, and different amounts of leaching losses of S from soil by rainfall. Within each year at each site, yield increases were mostly larger in spring (September–November) than in autumn (June–August). In the year of application, single superphosphate was equally or more effective than the other sources. In years when large responses to S occurred, applying single superphosphate later in the year was more effective than applying single superphosphate 3 weeks after pasture emerged (standard practice), so within each year the most recently applied single superphosphate treatment was the most effective S source. All sources generally had negligible residual value, so S needed to be applied each year to ensure S deficiency did not reduce pasture production.

Increased seed production of subterranean clover pastures in response to fertilizers supplying calcium

1974 ◽  
Vol 14 (71) ◽  
pp. 749 ◽  
Author(s):  
PG Ozanne ◽  
KMW Howes
Keyword(s):  
Seed Production ◽  
Calcium Concentration ◽  
Field Experiments ◽  
Seed Set ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Unit Weight ◽  
Gypsum Plaster ◽  
Total Seed ◽  
Seed Yields

The effects of four common fertilizers containing calcium on seed production in subterranean clover (Trifolium subterraneum) were measured at six locations over five years in a total of fifteen field experiments. Calcium as a sulphate, carbonate or phosphate salt was applied to subterranean clover pastures either at the start of the growing season (autumn) or at flowering (spring). Gypsum, plaster of Paris, or lime gave large increases in seed yield per unit area and also per unit weight of tops. Spring applications of superphosphate increased seed yields in only two out of four experiments. Gypsum applied in spring at 200-500 kg ha-1 was as effective as 2,000 kg ha-1 of lime applied in autumn. Applications of lime in spring were much less effective. Increased seed yields were due to increases in burr yield, seed number per burr, and mean weight per seed. They were usually accompanied by increases in calcium concentration in the seed. Responses in seed production to calcium applications were obtained in all three sub-species of Trifolium subterraneum. In two experiments, newly sown on a soil type on which subterranean clover regeneration and persistence is commonly very poor, applied calcium doubled or quadrupled seed set. In 13 experiments using soils on which subterranean clover had persisted as the major component of the pasture for several years, calcium in the year of application increased the total seed bank by 6 to 31 per cent, and the current seed set by a greater amount.

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.

Novel Disease Host Resistances in the World Core Collection of Trifolium subterraneum

Plant Disease ◽  
2020 ◽  
Author(s):  
Ming Pei You ◽  
Phillip Nichols ◽  
Roseline Katusiime ◽  
Martin John BARBETTI
Keyword(s):  
Core Collection ◽  
Morphological Traits ◽  
Phenotypic Expression ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Damping Off ◽  
Pythium Irregulare ◽  
Breeding Programs ◽  
Foliar Diseases ◽  
Disease Parameters

Glasshouse and field investigations were undertaken into the phenotypic expressions of resistance of a 97-member World Core Collection of subterranean clover (Trifolium subterraneum), collected from its native Mediterranean habitat and representing around 80% of the total genetic diversity within the known 10,000 accessions of the species, against the most important damping-off and root rot (Phytophthora clandestina, and Pythium irregulare) and foliar (Kabatiella caulivora, Uromyces trifolii-repentis and Erysiphe trifoliorum)pathogens. An additional 28 diverse cultivars were also included. Associations were also examined for these genotypes between 18 disease parameters and 17 morphological traits and between these disease parameters and 24 climatic and eco-geographic variables from their collection sites. Many genotypes showed strong phenotypic expression of novel host disease resistance(s) against one or more pathogens, enabling their potential deployment as disease resistant parents into subterranean clover breeding programs. These new sources of resistance enable future ‘pyramiding’ of different resistance genes to improve resistance against these pathogens. Of particular value were genotypes with multiple disease resistances across soilborne and/or foliar diseases, as many of these pathogens co-occur. All diseases had some parameters significantly correlated with one or more morphological traits and with one or more site of origin variables. In particular, there were significant negative correlations between damping-off (i.e., germination) and eight of the 17 morphological characters. The outcome of these studies provides crucial information to subterranean clover breeding programs, enabling them to simultaneously select genotypes with multiple resistances to co-occurring soilborne and foliar diseases, in addition to desirable traits, to offer renewed hope for re-establishing a more productive subterranean clover livestock feedbase despite multiple diseases prevailing widely.

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.

The effect of phosphate supply on the growth and botanical composition of annual type pasture

1964 ◽  
Vol 15 (1) ◽  
pp. 61 ◽  
Author(s):  
RC Rossiter
Keyword(s):  
Field Experiments ◽  
Total Yield ◽  
Indirect Evidence ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Residual Effects ◽  
Phosphate Deficiency ◽  
Phosphate Supply ◽  
High Phosphate

The results of two long-term field experiments and two 1-year experiments are reported. In three of these, severe phosphate deficiency was present initially. At high phosphate supply, the annual total yield was not significantly related to age of pasture over periods of 10–13 years. At intermediate and low supply, yields relative to high phosphate supply increased significantly with time; these increases are believed to demonstrate residual effects of phosphate. Indirect evidence for nitrogen accretion from clover under severely phosphate-deficient conditions is presented. Sward components—in the long term—responded differentially to phosphate supply. With very low phosphate, erodium (Erodium botrys (Cav.) Bertol.) and flatweed (Hypochoeris glabra L.) were dominant; whereas with high phosphate, cape-weed (Cryptostemma calendula (L.) Druce) and ripgut brome grass (Bromus rigidus Roth)—or else barley grass (Hordeum leporinum Link)—were dominant. Subterranean clover (Trifolium subterraneum L.), though present under these extremes, was relatively more plentiful at intermediate levels of supply. However, at "steady state" conditions, the range in clover content was fairly narrow (from c. 20 to 40%). The significance of these findings to a sheep infertility problem ("clover disease") of subterranean clover-dominant pastures is discussed.

Infection of subterranean clover swards with bean yellow mosaic potyvirus: losses in herbage and seed yields and patterns of virus spread

1994 ◽  
Vol 45 (7) ◽  
pp. 1427 ◽  
Author(s):  
RAC Jones
Keyword(s):  
Field Experiments ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Yield Losses ◽  
Grazing Experiment ◽  
Growing Seasons ◽  
Heavy Grazing ◽  
Herbage Yield ◽  
Seed Yields ◽  
Grazed Swards

During 1989-92, subterranean clover ( Trifolium subterraneum L.) was grown in field experiments in which swards of six cultivars were infected with bean yellow mosaic potyvirus (BYMV) by transplanting small BYMV-infected subterranean clover plants into them. The swards were then grazed by sheep or mown to simulate grazing. The infected transplants were the primary virus source for subsequent spread by aphids. Spread initially centred on infected transplants resulting in circular expanding infected patches. Later, secondary patches, isolated affected plants and more generalized infection sometimes developed. The extent of spread within swards from the transplants varied with cultivar, BYMV isolate, site and year. Final BYMV incidence ranged from 12% of plants symptom-affected by isolate MI in cv. Junee in 1991 to 100% by isolate SMB in cv. Leura in 1992. BYMV spread mostly occurred in spring and was increased around the edges of areas of bare ground in swards. In two experiments at one site in which 'mini swards' of cvv. Green Range, Karridale and Leura were mown repeatedly, BYMV-infection decreased herbage yields (dry weights) by 12-16% while seed yields were decreased significantly (by 37-40010) in one experiment. In a grazing experiment at a second site with swards of cvv. Esperance and Karridale, BYMV-infection decreased overall yields of herbage by 18-39% and seed by 11-12%; herbage yield losses within symptom-affected patches were 28-49%. In a further grazing experiment at this site with swards of cvv. Junee and Karridale, BYMV-induced losses determined from symptom-affected patches were 21-29% for herbage and 15-25% for seed. In a grazing experiment with swards of cvv. Denmark and ~ e u r a ' at a third site, BYMV-induced overall herbage yield decreases of 8-12% were still recorded despite extensive BYMV spread to control swards; yield losses within symptom-affected patches were 18-25% for herbage and 35-47% for seed. Seed yield losses were due to decreased seed size (mean seed weight), fewer seeds being produced, or both. Estimates of the effects of different levels of BYMV infection on herbage yields in partially infected grazed swards were obtained for cvv. Denmark, Karridale and Leura by plotting individual quadrat data for herbage dry weights against % symptom-affected plants. Losses increased in proportion to the level of infection, but their magnitude also varied with cultivar and experiment. It is concluded that BYMV infection of subterranean clover pastures is cause for concern, not only as regards herbage yield losses but also as regards depletion of the seed bank, which, when compounded year by year, results in pasture deterioration. Early and prolonged aphid activity, reseeding the pasture with susceptible cultivars, heavy grazing and extended growing seasons are all likely to magnify BYMV-induced losses.

Genetic improvement of subterranean clover (Trifolium subterraneum L.). 2. Breeding for disease and pest resistance

2014 ◽  
Vol 65 (11) ◽  
pp. 1207 ◽  
Author(s):  
P. G. H. Nichols ◽  
R. A. C. Jones ◽  
T. J. Ridsdill-Smith ◽  
M. J. Barbetti
Keyword(s):  
Plant Breeding ◽  
Mosaic Virus ◽  
Pest Resistance ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Yellow Mosaic Virus ◽  
Genotypic Differences ◽  
Pythium Irregulare ◽  
Halotydeus Destructor ◽  
Subterranean Clover Stunt Virus

Subterranean clover (Trifolium subterraneum L.) is the most widely sown pasture legume in southern Australia and resistance to important diseases and pests has been a major plant-breeding objective. Kabatiella caulivora, the cause of clover scorch, is the most important foliar fungal pathogen, and several cultivars have been developed with resistance to both known races. Screening of advanced breeding lines has been conducted to prevent release of cultivars with high susceptibility to other important fungal foliar disease pathogens, including rust (Uromyces trifolii-repentis), powdery mildew (Oidium sp.), cercospora (Cercospora zebrina) and common leaf spot (Pseudopeziza trifolii). Several oomycete and fungal species cause root rots of subterranean clover, including Phytophthora clandestina, Pythium irregulare, Aphanomyces trifolii, Fusarium avenaceum and Rhizoctonia solani. Most breeding efforts have been devoted to resistance to P. clandestina, but the existence of different races has confounded selection. The most economically important virus diseases in subterranean clover pastures are Subterranean clover mottle virus and Bean yellow mosaic virus, while Subterranean clover stunt virus, Subterranean clover red leaf virus (local synonym for Soybean dwarf virus), Cucumber mosaic virus, Alfalfa mosaic virus, Clover yellow vein virus, Beet western yellows virus and Bean leaf roll virus also cause losses. Genotypic differences for resistance have been found to several of these fungal, oomycete and viral pathogens, highlighting the potential to develop cultivars with improved resistance. The most important pests of subterranean clover are redlegged earth mite (RLEM) (Halotydeus destructor), blue oat mite (Penthaleus major), blue-green aphid (Acyrthosiphon kondoi) and lucerne flea (Sminthurus viridis). New cultivars have been bred with increased RLEM cotyledon resistance, but limited selection has been conducted for resistance to other pests. Screening for disease and pest resistance has largely ceased, but recent molecular biology advances in subterranean clover provide a new platform for development of future cultivars with multiple resistances to important diseases and pests. However, this can only be realised if skills in pasture plant pathology, entomology, pre-breeding and plant breeding are maintained and adequately resourced. In particular, supporting phenotypic disease and pest resistance studies and understanding their significance is critical to enable molecular technology investments achieve practical outcomes and deliver subterranean clover cultivars with sufficient pathogen and pest resistance to ensure productive pastures across southern Australia.

The effect of some environmental conditions on seed development and hard-seededness in subterranean clover (Trifolium subterraneum L.)

1979 ◽  
Vol 30 (1) ◽  
pp. 65 ◽  
Author(s):  
GB Taylor ◽  
MJ Palmer
Keyword(s):  
Seed Development ◽  
Seed Size ◽  
Field Experiments ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Moisture Stress ◽  
Effect Of Temperature ◽  
Temperature Regimes ◽  
Increasing Temperature ◽  
Dry Out

Subterranean clover (cv. Daliak) was grown in boxes with provision for unrestricted lateral growth. At the commencement of flowering, plants were allocated to three day/night temperature regimes of 12/7°, 18/13° and 24/19°C in controlled-temperature glasshouses and well watered until maturity (unstressed). In two additional treatments at 18/13°, plants were either subjected to intermittent moisture stress throughout the flowering period (stressed) or well watered for the first 6 weeks of flowering and then allowed to dry out (droughted). Increasing temperature resulted in more rapid inflorescence production, seed development and earlier plant maturation. The overall mean seed size was lower at 24/19° than at the other two temperatures. The stressed and droughted treatments produced fewer and smaller seeds than the corresponding unstressed treatment. There was a small effect of temperature on the degree of hard-seededness as determined from the mean softening time of seed subjected to daily alternating temperatures of 60/15°. Softening time was not significantly affected by watering treatments. There were small differences in softening time due to the position of the burr on the lateral, with a slight trend for seeds from the first-formed burrs to soften more rapidly. Most of the variation in softening time between seeds was due to variation within burrs. The sequence of seed softening within burrs was related to seed size, the larger seeds generally softening first, but no single regression could be used to describe this relationship for different burr positions or treatments. The absence of major treatment effects on the degree of hard-seededness indicates that varying the length of the seed development period does not necessarily result in differences in hard-seededness, as has been suggested from field experiments.

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.

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