Varieties Of Subterranean Clover Research Articles

Short- and long-term effects of low estrogenic subterranean clover on ewe reproductive performance

This study examined the short- and long-term effects on the reproductive performance of sheep by subjecting them to varieties of subterranean clover ( Trifolium subterraneum), containing a low content of total phytoestrogens and formononetin. In the first trial, 30 ewe lambs of the Sarda breed (initial mean live weight 16.4 ± 1.3 kg) were divided into three groups of 10 animals each and maintained separately on pastures for 60 d, with alfalfa ( Medicago sativa L.), oats ( Avena sativa), and subterranean clover with a phytoestrogen content ranging from 10.21 mg/g on a dry matter basis (DM) at the onset, to 0.90 mg/g DM at the end of the trial, respectively. All three pastures were integrated to make them isoproteic and isoenergetic. At the end of the grazing period, the animals were pooled into one group and fed the same phytoestrogen-free diet. No differences were recorded between the groups with regard to the development of the reproductive system as monitored by transvaginal ultrasonography, fertility, fecundity, breeding performance of the ewes, or with regard to the birth weight and conformation of the lambs. Puberty was attained earlier by the animals fed on subterranean clover, while the lambs also weighed more. In the second trial, 24 ewe lambs of the Comisana breed (initial mean live weight 25.0 ± 3.4 kg) were divided into two groups of 12 animals each. All animals were fed ad libitum for a 20 months period with fresh-cut or dried subterranean clover (phytoestrogen content of 0.88 and 0.81 mg/g DM, respectively); or a control non-estrogenic diet, based on fresh-cut or dried Italian ryegrass ( Lolium multiflorum Lam.). The two diets were integrated so to be isoenergetic and isoproteic. No differences were recorded between the groups with regard to the attainment of puberty, although the animals fed clover were heavier at puberty. The development of the reproductive system, fertility, fecundity and breeding performance in both lambings, the interval between lambings, and body weight and conformation of the lambs did not show differences. In both trials, neither non-degraded phytoestrogens nor equol (metabolite of formononetin) were recorded in the blood of the ewes. The only metabolite present was p-ethylphenol. All animals fed subterranean clover-based diets, showed a significantly higher ADG, compared to those fed the control diets. The results of this study indicate that the levels of total phytoestrogens and formononetin in the new varieties of subterranean clover do not negatively affect the reproduction of sheep and appear to improve the growth rate of the animals.

The expression of resistance in subterranean clover (Trifolium subterraneum) to races 1 and 2 ofKabatiella caulivorais affected by inoculum pressure but not by combinations of the two races

The performance of subterranean clover (Trifolium subterraneum) varieties in the field in the presence of the clover scorch pathogen, Kabatiella caulivora, can be highly variable in terms of the disease levels that develop. Although the influence of environmental conditions on development of this disease is documented, the influence of inoculum pressure or race combinations has not previously been investigated. Hence, separate controlled environment studies were undertaken to identify the effects of inoculum concentration and the effects of race combinations upon the expression of resistance to clover scorch disease in seedlings of seven subterranean clover varieties. In relation to the percentage of petioles with lesions following inoculation with different conidial concentrations of either race 1 or race 2 of K. caulivora, there was a significant effect of races (P<0.001), varieties (P<0.001) and of inoculum concentration (P<0.001) and also a significant interaction between races and varieties (P<0.001), and of inoculum concentration with varieties (P<0.05). Although levels of disease observed on the varieties tested were generally comparable to those observed in the field, the findings in relation to inoculum concentration may explain why the performance of some subterranean clover varieties in the field in the presence of the clover scorch pathogen can be highly variable, as evidenced by certain incidences of severe disease and/or collapses of field swards of Meteora and Karridale varieties in Western Australia. When inoculated with varying proportions of race 1 and race 2, there was a significant effect of race combination treatments (P<0.001), but there was no indication of any additive or interference effects between the two races when present together as a combination on the same plant in relation to host expression of resistance to each individual race. Together, these studies showed, for the first time, that expression of resistance to K. caulivora in subterranean clover is dependent on pathogen inoculum level but independent of the races present as mixtures. The implications of these studies are 3-fold. First, that variable expression of resistance in the field is related to inoculum pressure. Second, that seedling resistance to individual races should be able to be identified even where both races occur together in combination, eliminating the current expensive requirement of utilising a separate field screening site for each race. Third, these results indicate that while effective deployment of host resistance is particularly rewarding where cultural and/or chemical strategies are in place to keep the inoculum of the pathogen at manageable levels, it can also be rewarding even under high inoculum pressure.

Mineral nitrogen supply from pastures to cereals in three northern Victorian environments

An experiment at 3 sites (Birchip, Elmore and Speed) in the northern Victorian cropping belt compared dry matter (DM) production of short-term (2 year) pastures and their contributions to soil mineral nitrogen (N) and subsequent wheat and barley production. The pastures included different varieties of subterranean clover, annual medic and lucerne, and these were compared with ryegrass-dominant pasture, which represented the experimental control. More productive legume pastures generally resulted in greater accumulation of soil mineral N at sowing of the following cereal at both Elmore and Speed; however, at Birchip, soil mineral N remained high under all treatments. At Elmore and Speed, significant (P&lt;0.10) positive relationships were observed between available N at sowing and subsequent wheat and barley production. Cereal grain yield at Birchip was not associated with available N at sowing. The quantities of soil mineral N available at sowing (152 kg/ha) of the cereals were in excess of crop demand at Birchip. At Elmore, the soil mineral N supply (83 kg/ha) was below that required for wheat and barley to reach their water-limited potential yield (20 kg grain/mm of growing season rainfall). However, at Speed, the supply of soil mineral N (63 kg/ha) was sufficient to achieve the water-limited potential grain yield and to produce malting-grade barley, but not sufficient to elevate wheat grain protein concentrations above 11.5%. In environments with low soil N levels, the amount of residual N following short-term pastures increased the availability of N to following cereals. Whether this is sufficient to satisfy subsequent crop demand is largely determined by water availability in the year of cropping. In cases where available N is already high, short-term pasture phases may have little effect on increasing crop production.

Induced responses in clover to an herbaceous mite.

Halotydeus destructor feeding on subterranean clover cotyledons can cause severe damage. The mites live on the soil surface and move up onto plants to feed. Foraging behaviour consists of palpating, probing, and feeding with frequent transitions between them. Sustained feeding is made up of a series of short (1-2 min) feeds separated by periods of palpating. The mites tend to feed in aggregations, and are attracted to cotyledons damaged by other mites feeding or by mechanical damage. Mites can distinguish between resistant and susceptible cotyledons within 30 min and resistance is antixenotic due to deterrence. Study of the mechanisms shows this to be induced plant resistance. Several green leaf volatiles are involved in the plant/mite interaction. After feeding commences, 2-E-hexenal is released that at low concentrations is attractive to mites, perhaps causing the feeding aggregations. The wound-induced C(8) compound, 1-octen-3-one, plays a significant role in the deterrence of cotyledons of resistant subterranean clover varieties to H. destructor. Damaged cotyledons of resistant varieties produce more 1-octen-3-one that those of susceptible varieties. Screening for resistance has identified varieties from Italy showing resistance. H. destructor does not occur in Europe. Production of damage-induced volatiles by the resistant plants may have resulted from invasion by herbivores or pathogens, but not from coevolution with these mites. The responses of H. destructor are probably an adaptation to these general plant defensive compounds.

Antixenotic resistance of subterranean clover cotyledons to redlegged earth mite, Halotydeus destructor

AbstractThe short‐term response of redlegged earth mite, Halotydeus destructor (Tucker) (Acarina: Penthaleidae) to cotyledons of different varieties of subterranean clover (Trifolium subterraneum subsp. subterraneum L.) was assessed by means of paired choice tests, and no‐choice tests. H. destructor had lower numbers and fed less on detached cotyledons of resistant than susceptible varieties, yielding a correlation between the numbers of mites and feeding damage to the cotyledons during a three hour test period. For a number of resistant and susceptible varieties, there was a negative correlation between cotyledon deterrence in the three hour choice test and feeding damage to seedlings after a two week period. Since the response of the mites to different subclover varieties occurred within three hours, it is concluded that the resistance is based on antixenosis.No evidence was obtained for antifeedant activity in organic solvent extracts from the variety DGI007 (resistant) in comparison with those from the variety Dalkeith (susceptible). Water soluble compounds from DGI007 cotyledons were preferred by mites, in feeding tests in terms of numbers, over those from Dalkeith (susceptible). Squeezed sap from the cotyledons of both varieties showed the same effects on mites as 5% glucose and were more phagostimulatory than water extracts. Mechanically damaged cotyledons of Dalkeith and DGI007 attracted more mites than the undamaged counterparts. The toughness of cotyledons in 17 varieties of T. subterraneum subsp. subterraneum was measured with a manual penetrometer. Results showed a negative correlation between toughness values and mite feeding damage scores (r2 = 0.752) for all varieties except S3615D (resistant). This implies a likely involvement of epidermal toughness as a contributor in the antixenotic resistance of these varieties. Other mechanisms may be involved in the resistance of S3615D.

Comparison of 32 Cover Crops in an Organic Vineyard on the North Coast of California

ABSTRACT In a replicated study conducted from 1990 to 1992, cover crops and a control (resident vegetation) were evaluated in an organic wine-grape vineyard (cv. ‘Chardonnay’), located at a valley floor site in Hopland, Mendocino County, California. The purpose was to assess plant phenology, stature, biomass production, competitiveness with resident vegetation, and second-year stand regeneration or persistence in an unfilled vineyard. Legumes (Fabaceae) evaluated included nine annual and two perennial types of clover (Trifolium spp.), bell bean and three other types of Vicia, two types of coolseason annual medic (Medicago spp.), field pea (Pisum sativum ssp. arvense), a mixture of biennial sweetclovers (Melilotus alba and M. officinalis), broadleaf birdsfoot trefoil (Lotus comiculatus). There were six types of cool-season annual grasses (Poaceae) including three cereal grains. Native Californian perennial grasses included one rhizomatous and five bunch types. The sole representative of Brassicaceae was black mustard (Brassica nigra). Unseeded, resident vegetation plots served as a control. In the first year after seeding, all cover crops except purple needlegrass (Nassella pulchra) established stands. Observations of phenological state suggested particularly advanced seed maturity by early May for the annual grasses barley, rattail fescue, soft chess, and cereal rye, as well as for burr medic and ‘Dalkeith’ subterranean clover. By contrast, ‘Austrian Winter’ field pea, berseem clover, biennial sweetclovers, and perennial legumes had not begun flowering. Other entries were at various stages of flowering. Height was generally greatest for black mustard followed by annual grasses, perennial grasses, vetches, field pea, and was similar for annual clovers and medics. Eighteen cover-crop regimes produced vegetational cover in excess of 90%. Particularly great percentages of vegetational cover were obtained for control (resident vegetation), common vetch (Vicia sativa), annual ryegrass (Lolium multiflorum), oat (Avena sativa), and berseem clover (Trifolium alexandrinum). Particularly small percentages of vegetational cover by cover crops occurred (in increasing order) for creeping red fescue (Festuca rubra cv. ‘Molate’), broadleaf birdsfoot trefoil, and biennial sweetclovers. Particularly great biomass estimates were obtained (in decreasing order) for barley (Hordeum vulgare), oat, black mustard, purple vetch (Vicia beghalensis), rye, ‘Koala’ subterranean clover (Trifolium subterraneum ssp. brachycalycinum) soft chess (Bromus hordeacens), woollypod vetch (Vicia villosa ssp. dasycarpa), and common vetch (Vicia sativa). Especially low biomass production was observed (in increasing order) for creeping red fescue (Festuca rubra), biennial sweetclovers, strawberry clover, meadow barley, and the mix of ladino and strawberry clovers. Biomass for resident vegetation in the control plots was significantly greater than biomass produced by creeping red fescue. In the second May following seeding, cover crop stands were inspected visually and regeneration scored qualitatively and subjectively as none, very poor, poor, fair, good, and very good. Percentage of vegetational cover by crops was also assessed visually. Stands scored as having good or very good regeneration were assessed for biomass as in 1991. The following entries attained good or very good regeneration: soft chess, California brome, annual ryegrass, both forms of blue wildrye, oat, cereal rye, crimson clover, four varieties of subterranean clover, and both the mixture of ladino and strawberry clovers and the sole seeding of strawberry clover. Particularly great biomass values were obtained for crimson clover and for ‘Mt. Barker’ and ‘Trikkala’ subterranean clovers. None of the three vetches attained high percentages of cover in the second year; these are thought to benefit from tillage, which was not used in this study. Biomass readings were, for the most part, lower than in 1991. This may have been due to low soil moisture during autumn as a result of a lack of irrigation and rain.

Responses and feeding damage of redlegged earthmite (Acarina: Penthaleidae) to seedlings of resistant and susceptible subterranean clover varieties

Responses of redlegged earth mite (Halotydeus destructor) to seedlings of three resistant and four susceptible varieties of subterranean clover (Trifolium subterraneum) were measured after 7 or 14 days in pot experiments in the glasshouse. With a single variety/pot, mites on resistant varieties (DGI007, EP145SubD and Rutherglen B) produced 45% of the progeny that were produced by mites on the susceptible varieties (89838G, Dalkeith, Junee and 70088B). Number of stages completed and survival were little affected by varieties. Feeding damage (silvering of cotyledons) on resistant varieties averaged 45% of that on susceptible varieties with a single varietylpot. H. destructor fed less on resistant varieties in choice than in single variety experiments. On Junee and 89838G seedlings, feeding damage was similar to that on other susceptible varieties, but there were about half as many H. destructor progeny as on Dalkeith and 70088B. Mites laid more eggs on soil away from Junee plants, compared to the other three susceptible varieties. Different factors adversely affected the number of progeny produced on resistant varieties and on Junee.

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

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.

798 PB 074 CHANGES IN WEED SPECIES WITH DIFFERENT COVER CROPS IN TWO CALIFORNIA VINEYARDS

Cover crops are grown in vineyards for many reasons, including erosion control, maintaining organic matter and changing pest complexes. Changing a management practice from using resident vegetation as a cover to other planted cover crops will change the vineyard floor flora. The cover crops of `Olge' oat, `Olge' oat and purple vetch, and purple vetch alone were compared to resident vegetation as winter planted cover crops. The cover was harvested in April of each year and blown under the vine row; The cover crop remains were disked into the middles after mulching. Three varieties of subterranean clover were planted in the vine rows at each location in one-half of each of the cover crops. The winter annual weed species, black and wild mustard, common chickweed and annual bluegrass decreased in the inter-row areas. The perennial weed field bindweed increased in all cover crop treatments.

Herbage and seed yield losses in six varieties of subterranean clover from rust (Uromyces trifolii-repentis)

Studies were conducted to determine the herbage and seed yield losses caused by rust (Uromyces trifolii-repentis Liro) in field plots of 6 subterranean clover varieties. By early October (mid spring), rust caused large reductions in herbage production in varieties Green Range (25.9%), Mount Barker (24.8%), Woogenellup (20.3%), Mulwala (18.7%) and Karridale (15.2%). By the beginning of November (late spring), herbage yield losses were greater in Mulwala (50.5%), Green Range (49.4%), Woogenellup (36.9%) and Mount Barker (34.1%). Rust also caused large reductions in seed yield in Green Range (89.4%), Mulwala (84.8%), Karridale (70.2%), Woogenellup (67.2%) and Mount Barker (39.5%). The variety Larisa was highly resistant to rust, with no significant (P&gt;0.05) reduction in herbage or seed yield.

Susceptibility of subterranean clover varieties to powdery mildew under controlled environment and field conditions

Thirty-three subterranean clover varieties, comprising 16 commercial cultivars and 17 promising midseason breeding and introduced lines, were screened for resistance to powdery mildew (caused by Erysiphe polygonii) under controlled environment conditions, and where possible, comparisons were made with their performance in field plots. There were large differences between varieties in the incidence and severity of powdery mildew on plants. Under controlled environment conditions, Tallarook, CPI 47308C, CPI 89860D, 75S13-12, CPI 6.53284 CPI 89820D and Clare had the lowest levels of leaf infection, the lowest mildew sporulation scores and the least amount of leaf scorching from mildew infection. Karridale had the highest level of leaf infection, followed by 69837-1, 76841-1, Junee, Bacchus Marsh and 69S37-3. Under field conditions, Tallarook, CPI 47308C, CPI 65328A and CPI 65328F were mildew-free, while CPI 89777C, CPI 89860D, CPI 89830F, CPI 89841E, Clare and Rosedale had good resistance. Junee was clearly the most susceptible under field conditions, followed by 76S41-1, 69837-3, Karridale, Bacchus Marsh and 69S37-1. There was generally excellent correlation between the different powdery mildew disease parameters, namely leaf infection, mildew sporulation and leaf scorch, measured under controlled environment conditions, and there was also good overall correlation between controlled environment and field data. Bacchus Marsh, Junee, 69337-1, 69837-3 and 76341-1 were highly susceptible under both controlled environment and field conditions, indicating that either environment could be used to identify highly susceptible varieties. Under controlled environment conditions, a high degree of resistance was observed in Clare, CPI 47308C, CPI 65328A, CPI 89820D, CPI 89860D and 75S13-12, while field plots of the varieties Tallarook, CPI 47308C and CPI 65328A showed a complete absence of powdery mildew. These varieties may have value as parents in breeding programs for powdery mildew resistance.

Susceptibility of subterranean clover varieties to rust under controlled environment and field conditions

Thirty-two subterranean clover varieties, comprising 17 commercial cultivars, 1 named variety and 14 promising midseason breeding and introduced lines, were screened for resistance to rust (caused by Uromyces trifolii-repentis) under controlled environment conditions, and where possible, comparisons were made with their performance in field plots. There were large differences between varieties in the incidence and severity of rust on plants. Under controlled environment conditions, cvv. Gingin, Meteora and Enfield, and to a lesser extent Larisa and Trikkala, had the lowest levels of rust leaf infection, the lowest rust pustule densities and the smallest rust pustules. Seaton Park had a relatively low pustule density and CPI 89830F had relatively small pustules. Gingin and Enfield had the least leaf collapse. Green Range was the most susceptible under controlled environment conditions, followed by Bacchus Marsh, Karridale, CPI 47308C and CPI 89841E. Under field conditions, Enfield, Meteora, Trikkala and CPI 89822H were rust free, while Larisa, CPI 47308C, CPI 65328F, 75S13-12, 76841-1, CPI 89830F and CPI 89880J had good resistance. Green Range was clearly the most susceptible under field conditions, followed by Seaton Park, Karridale, Bacchus Marsh, CPI 89774F and CPI 89841E. While there was often good correlation between the field and controlled environment data for the different parameters, the resistance rankings of some varieties varied widely, depending upon whether screened under controlled environment or field conditions. Green Range, Karridale, Seaton Park and CPI 89841E were highly susceptible to rust under both controlled and field conditions, indicating that either environment could be successfully used to identify highly susceptible varieties. The high degree of resistance observed in Enfield, Gingin and Meteora, and to a lesser extent in Larisa and Trikkala, suggests their value as parents in breeding programs for rust resistance.

Response of subterranean clover varieties to Cercospora disease under a controlled environment and in the field

Seventeen commercial cultivars of subterranean clover and 10 introduced lines were screened for resistance to cercospora disease (caused by Cercospora zebrina) under a controlled environment, and responses were compared with their performance in the field. There were large differences between varieties in the severity of cercospora disease under both conditions. There was, overall, good correlation between data from the field and those from the controlled environment for the different parameters. Daliak, Dalkeith, Esperance, Mt Barker, Nungarin and Rosedale were highly susceptible to cercospora disease under both controlled environment and field conditions, while Clare, Larisa, Meteora and Yarloop were assessed as having a high degree of resistance under both conditions. A few individual resistance rankings varied widely between the 2 conditions. The results indicate that controlled conditions can be used to identify resistant lines.

Effect of Kabatiella caulivora isolates and host growth stage on symptom expression and resistance in Trifolium subterraneum

Occasional severe clover scorch disease outbreaks from Kabatiella caulivora have occurred in the 2 partially resistant Trifolium subterraneum cultivars, Karridale and Meteora. All K. caulivora isolates screened, including isolates taken from severely damaged field swards of Karridale and Meteora, were highly pathogenic, but there was variation in the pathogenicity of some isolates and there was a significant cultivar x isolate interaction in 1 of 2 studies. Plant age affected development of disease. Cultivars Karridale, Mt Barker and Woogenellup were least susceptible when inoculated 10 weeks from sowing, and there was a strong plant age x cultivar interaction. However, there was no suggestion that severe disease in Karridale was due to increased susceptibility at a particular plant growth stage. In resistance screening studies, the resistance rankings of subterranean clover varieties sometimes changed markedly depending upon the test isolate, and in 1 of 2 studies, there was a significant cultivar x isolate interaction. While there was significant overall correlation between glasshouse and field data, this only accounted for 49.9 and 20.5%, respectively, of the variation. Glasshouse screening was not suitable for replacing field screening but it was useful for confirming the field resistance of some highly resistant genotypes.

Seed yield and seed quality of subterranean clover (Trifolium subterraneum L.) in growing conditions of Finland

Seed yield and overwintering of seeds of 22 Australian subterranean clover varieties were investigated in 1986 and 1987 at the Viikki Experimental Farm of the University of Helsinki. The seed yield varied remarkbly according to the variety and weather conditions of the two summers. Some varieties, such as Seaton Park, Woogenellup and Karridale, and during the summer of 1987 also the early variety Dalkeith, produced lots of seed. Some late varieties, e.g. Treeton, Tallarook and Esperance, produced very few seeds or no seeds at all. A considerable proportion of the seeds degenerated during the wet autumn conditions, by the end of October. Many seeds showed embryo dormancy, but complete dormancy or hard seeds were found only exeptionally. In spring 1988, some seedlings which had developed from overwintered burrs were found. There seems to be little hope of finding self-seeding subterranean clovers suitable for Finnish growing conditions.

Studies in uterotrophic activities in strains of subterranean clover

Uterotrophic responses in ovariectomized ewes when fed or grazed on Mount Barker, Yarloop or Dwalganup varieties of subterranean clover are reported. The high formononetin varieties Dwalganup and Yarloop always elicited a uterotrophic response. The low-formononetin, high-genistein and biochanin A variety, Mount Barker, stimulated a uterotrophic response, using a 5-day bioassay, when fed at 200g/day or 800g/day, but little or no response when grazed. When chopped lucerne hay was offered with 200 g of the Mount Barker the uterotrophic response was suppressed and the mean uterine weight was not significantly different from that of the negative controls (P= 0.57). The uterine weight of sheep eating 200 g/day of Yarloop and offered lucerne chaff or pellets in one experiment was lower (but not significantly lower) than the unsupplemented group. This trend may be worthy of further investigation.

Effect of burial on the softening of hard seeds of subterranean clover

Burrs of eight varieties of subterranean clover (Trifolium subterraneum L.), which had experienced one summer at the soil surface, were placed on the soil surface and at depths of 2, 6 and 10 cm in the soil. The numbers of residual hard seeds were determined after 1, 2 and 3 years. The effects of laboratory treatment at a diurnally fluctuating temperature of 60/15�C on the softening of buried seeds and of seeds stored in the laboratory for 1 and 3 years were determined. Rate of seed softening in all varieties decreased with increasing depth of burial, apparently because the soil insulated the seeds from high soil surface temperatures. Few seeds of the varieties Northam and Geraldton softened during 3 years of burial at 6 or 10 cm; while, at the other extreme, few seeds of Yarloop survived 3 years at any depth. Some evidence was found for microbial decomposition of hard seeds in the field. Seeds softened more readily at 60/15�C (in the laboratory) as the preceding periods of either laboratory storage or field burial increased. Such storage or burial experiences have a preconditioning effect on hard seeds, making them more amenable to softening once they are subjected to wide diurnal temperature fluctuations. The results indicate that soil tillage associated with cropping should build up a useful soil seed reserve of the harder seeded varieties.

Long term patterns of seed softening and seedling establishment from single seed crops of subterranean clover

Single seed crops of eight varieties of subterranean clover (Trifolium subterraneum) were grown in swards in four successive years in a medium rainfall environment at Bakers Hill, Western Australia. Measurements were made of seed production, the progress of seed softening within the first two summers, and residual hard seed and seedling numbers after the break of season for up to six successive regeneration years. Patterns of seed softening were also measured in a laboratory oven with a diurnal temperature fluctuation of 60/15�C. Approximately half the seeds of all varieties softened over the first summer and generally well over half the residual seeds softened during the second summer. Up to 18% of seeds of the hardest seeded variety, Northam, and 11% of Geraldton seeds persisted to the end of the third summer as hard seeds. Seed softening patterns showed a significant variety x regeneration year interaction due mainly to a slower rate of softening of Northam seeds relative to the other varieties after the first summer. In six of the varieties, seeds generally softened more slowly in the laboratory than in the field but in the case of the other two varieties this trend was reversed. Nevertheless, ranking of varieties for rate of seed softening was similar in field and laboratory. Seedling establishment ranged from 28 to 100% of soft seeds, depending on the incidence of late summer and autumn rains. It appeared that all varieties in the study would regenerate satisfactorily at densities of more than 15 plants/dm2 after at least one year in which little or no seed is set. Slower rates of softening would probably be desirable in drier regions or in rotation systems involving cropping.

The flowering of annual legume pasture species and cultivars in Western Australia

A total of 31 separate annual medic species or varieties of subterranean clover was sown at three planting dates April, May and June, at six sites and for two consecutive years; the time to commencement of flowering was recorded. With each species or variety there were major differences according to site and planting date. There were also agronomically significant interactions between species or variety, site, and planting date. The differences are ascribed primarily to temperature variability but there was some evidence also of a latidude effect perhaps due to day length. There were some varieties, e.g. Dinninup, with unusual flowering patterns not explainable on the basis of vernalization requirement alone.

Potential of Serradella as a winter annual forage legume on sandy coastal soil

Abstract Three species of Serradella, Ornithopus sativus. O. pinnatus, and O. compressus cv. ‘Pitman’, each at diploid and tetraploid levels, were compared with two varieties of subterranean clover, ‘Mt. Barker’ and ‘Tallarook’, on Himatangi sandy soil. Productivity ciata are presented for mown plots for the second year of a trial in which the legumes were permitted to reseed naturally. Reseeding of the diploid serradellas and the subterranean clovers was excellent. Tetraploid O. compressus cv. ‘Pitman’ reseeded sufficiently to produce a sward in the second year, but tetraploid O. sativus and O. pinnatus failed to re-establish naturally and were resown by hand. O. sativus at both ploidy levels outyielded all other lines by about 2000 kg DM/ha (25%). Diploid O. compressus cv. ‘Pitman’ and ‘Tallarook’ subterranean clover each produced about 8000–9000 kg DM/ha. Tetraploid cv. ‘Pitman’, both lines of O. pinnalus, and ‘Mt. Barker’ were inferior. These results indicate that further evaluations of Serradella on ...