Perennial Ryegrass Varieties Research Articles

Comparison of growth and carbohydrate accumulation in seedlings of two varieties of Lolium perenne

Following the identification of suitable traits, the genetic basis of physiological processes such as growth and carbohydrate accumulation can be examined with QTL analysis. Seedling growth was studied in two varieties of perennial ryegrass ( Lolium perenne L.) at two stages (following germination and after defoliation) during transitions from reserve-driven growth to current-photosynthate-driven growth. Total water-soluble carbohydrate contents of leaf blades, sheaths and roots were also measured. Aurora (a high-sugar variety) was capable of rapid growth, and grew faster than Perma when growth was reserve-driven. Perma had a low reserve carbohydrate content and grew slowly when growth was reserve-driven. When growth was fuelled by current photosynthate, Perma grew faster than Aurora and replaced its carbohydrate reserves more rapidly. Changes in growth rate appeared to precede changes in water-soluble carbohydrate content. It is concluded that the extent of water-soluble carbohydrate accumulation was inversely related to constitutive growth rate, and that neither process appeared to be limited by photosynthate supply. Traits amenable to QTL analysis are identified.

Overseeding endophytic perennial ryegrass into stands of Kentucky bluegrass to manage bluegrass billbug (Coleoptera: Curculionidae).

Studies were conducted to determine the utility of overseeding endophyte enhanced varieties of perennial ryegrass, Lolium perenne L., into existing stands of Kentucky bluegrass, Poa pratensis L., to manage bluegrass billbug, Sphenophorus parvulus Gyllenhal, larval populations and their damage. Two commercial varieties of endophyte enhanced perennial ryegrass (Repell II and Triple Play) were overseeded at two different rates in the field. S. parvulus larval populations, their damage, and turfgrass composition were monitored over the course of 3 yr. Significantly fewer larvae were found in plots overseeded with Repell II, whereas Triple Play had no significant effect on larval population density. Endophyte infection was confirmed in approximately 58% of all Repell II shoots, whereas only approximately 31% of Triple Play shoots were infected. Regression analysis, using a segmented model, demonstrated that larval populations declined as the proportion of endophyte-infected perennial ryegrass increased. However, no additional reductions in larval population density were achieved in stands containing >40% endophyte-infected perennial ryegrass. Visual damage varied with cultivar, seeding rate, and year, but generally decreased as the proportion of endophyte-infected perennial ryegrass increased. Although seeding rate had an initial effect on turfgrass composition, these differences were not detected after the first year of the study. Results indicate overseeding existing stands of Kentucky bluegrass with endophytic varieties of perennial ryegrass can reduce S. parvulus larval populations and their damage. However, plant genetic characteristics (i.e., different cultivars) may be overriding determinants of many aspects of plant performance including establishment, tolerance to insect feeding, and expression of endophyte-mediated resistance.

Effect of sward cutting management on the relative performance of perennial ryegrass varieties

The performance potentials of six perennial ryegrass varieties for conservation or grazing use were compared between 1994 and 1996 in N. Ireland. They were maintained, either under constant lax defoliation (conservation) or constant severe defoliation (simulated grazing) management for 3 years, or annually alternated between these two managements with the changeover taking place either in autumn or at the first cut of the following year. Starting one set with lax defoliation in the first year and the other with severe defoliation created duplicates of these two alternating treatments. The results showed that variety yield differed depending on the season and the management imposed and there were differential responses to the various treatments. Conducting an alternating management system that implemented the management change in autumn provided a valid estimate of yield performance potential for both simulated grazing and conservation use, compared to constant management systems. Although significant differences in variety ranking between lax defoliation and severe defoliation management yields were only observed in the third year, the study showed that if the management change was implemented in autumn, the yield potential of varieties in the following year was not affected by the preceding year's management regime. Leaving a longer sward (6 cm) to over-winter increased the spring performance of the varieties in some years, compared to a shorter sward (3 cm), which may have implications for grazing management. There were also indications that imposing an alternating management system might alter the absolute magnitude of the sward density ratings relative to a constantly managed system, though variety rankings would remain unaffected.It was concluded that the current alternating management testing system used to evaluate candidate varieties for UK National or regional recommended lists, does not cause any variety to be unfairly advantaged or disadvantaged.

Differences in the nitrogen use efficiency of perennial ryegrass varieties under simulated rotational grazing and their effects on nitrogen recovery and herbage nitrogen content

Eight varieties of perennial ryegrass (six new varieties and two old ones) grown at five levels of applied fertilizer (100, 200, 300, 400 and 500 kg of N ha–1) were cut monthly during two growing seasons (March to October in 1997 and 1998) and their herbage dry‐matter (DM) yield and nitrogen (N) content were determined. Herbage leaf content and the N content of young fully expanded leaves were also measured in 1997, and monthly recovery of applied N was determined in both the first and second harvest years by using 15N.The rank order of varieties was similar for annual yield of DM and N at all five fertilizer levels. Proportional differences between varieties in DM yield were greatest in the first cut of each year, the late‐heading candidate variety Ba12151 out‐yielding the old late‐heading variety S23 by more than 70%. However, differences in annual DM yield were much more modest than in early spring yield, up to 10% in 1997 and up to 21% in 1998. The relatively small differences in total annual DM yield were attributed to only a small proportion of the applied N being recovered during a single regrowth period, most of the remainder becoming available for uptake in subsequent regrowth periods.There were small but highly statistically significant differences among varieties in the N content of their leaves, leaf N content being inversely related to yield of DM and N. This lends further support to the hypothesis that the metabolic cost of protein synthesis and turnover is a key factor controlling genetic variation both in leaf yield and in annual DM and N yield under frequent harvesting. Seasonal variation in herbage N content was much greater than differences among varieties in mean N content over all harvests. In May of both years at all applied fertilizer levels, herbage N content fell below the 20 g N kg–1 DM level required by productive grazing animals.

Milk production from dairy cows offered perennial ryegrass selected for high water soluble carbohydrate concentrations compared to a control grass

The efficiency of grass nitrogen utilisation for milk production tends to be low, due partly to the slow rate of release of energy in the rumen which reduces the efficiency of capture of rapidly degradable plant proteins by the rumen microbial population. When additional sugars are infused into the rumen, microbial protein production is increased (Rooke et al., 1987). The objective of this study was to assess milk production using a grass variety that has been bred to express elevated water soluble carbohydrate (WSC) concentrations.Eight multiparous Holstein-Friesian dairy cows in mid lactation (176 days ± s.e. 3.6) were used in a continuous design, zero-grazing experiment. Following covariate measurements taken from all animals on a standard grazing diet, four animals were each offered one of two varieties of perennial ryegrass at ad libitum rate: AberDove, bred to express high WSC concentrations; and AberElan, a commercially available variety, used as a control.

The effect of drying temperature on in vitro dry‐matter digestibility and water‐soluble carbohydrate content of perennial ryegrass varieties

In official forage grass variety trials in the UK, herbage samples are dried at 100°C or more to facilitate quick drying of the large numbers of samples that are currently needed. When assessing herbage quality, however, 80°C has been recommended as the highest temperature that can be used during drying without serious deterioration. Herbage from six perennial ryegrass varieties, which were known to show a range of variation in in vitro concentration of digestible dry matter (DMD) and water‐soluble carbohydrate concentration (WSC) during the vegetative phase of growth, was dried in an oven with forced ventilation at 100°C and at 80°C before analysis. Mean DMD over all varieties was slightly lower [6 g kg−1 dry matter (DM)] and mean WSC over all varieties was considerably lower (24 g kg−1 DM) at 100°C. Varieties differed in mean DMD over both drying temperatures by 37 g kg−1 DM and in mean WSC by 63 g kg−1 DM. There was, however, no significant interaction between variety and drying temperature for either DMD or WSC. Although drying at the higher temperature underestimated both DMD and WSC, it did not significantly alter the ranking of varieties or the range among them.

Performance of white clover/perennial ryegrass mixtures under cutting

Clover persistence in mixtures of two varieties of perennial ryegrass (Lolium perenne) with contrasting growth habits and three white clover (Trifolium repens) varieties differing in leaf sizes was evaluated at two cutting frequencies. An experiment was sown in 1991 on a clay soil. The plots received no nitrogen fertilizer. In 1992, 1993 and 1994, mixtures containing the large‐leaved clover cv. Alice yielded significantly more herbage dry matter (DM) and had a higher clover content than mixtures containing cvs Gwenda and Retor. Companion grass variety did not consistently affect yield or botanical composition. Cutting at 2 t DM ha−1 resulted in slightly higher total annual yields than cutting at 1.2 t DM ha−1, but did not affect clover content. In 1992 the mixtures yielded, depending on cutting frequency and variety, 10·6–14·6 t DM ha−1 and 446–599 kg ha−1 N, whereas grass monocultures yielded only 1·2–2·0 t DM ha−1 and 25–46 kg ha−1 N. From 1992 to 1994 the annual mean total herbage yield of DM in the mixtures declined from 12·2 to 10·5 to 8·7 t ha−1, the white clover yield declined from 8·7 to 6·5 to 4·1 t ha−1 and the average clover content during the growing season declined from 71% to 61% to 46%, whereas the grass yield increased from 3·4 to 4·0 to 4·5 t ha−1. The N yield decreased from 507 to 406 to 265 kg N ha−1 and the apparent N fixation from 470 to 380 to 238 kg N ha−1. Nitrate leaching losses during the winters of 1992–93 and 1994–95 were highest under mixtures with cv. Alice, but did not exceed 10 kg N ha−1. The in vitro digestible organic matter (IVDOM) was generally higher in clover than in grass, particularly in the summer months. No differences in IVDOM were found among clover or grass varieties. The experiment will be continued to study clover persistence and the mechanisms that affect the grass/clover balance.

Performance of white clover/perennial ryegrass mixtures under cutting

Clover persistence in mixtures of two varieties of perennial ryegrass (Lolium perenne) with contrasting growth habits and three white clover (Trifolium repens) varieties differing in leaf sizes was evaluated at two cutting frequencies. An experiment was sown in 1991 on a clay soil. The plots received no nitrogen fertilizer. In 1992, 1993 and 1994, mixtures containing the large-leaved clover cv. Alice yielded significantly more herbage dry matter (DM) and had a higher clover content than mixtures containing cvs Gwenda and Retor. Companion grass variety did not consistently affect yield or botanical composition. Cutting at 2 t DM ha−1 resulted in slightly higher total annual yields than cutting at 1.2 t DM ha−1, but did not affect clover content. In 1992 the mixtures yielded, depending on cutting frequency and variety, 10·6–14·6 t DM ha−1 and 446–599 kg ha−1 N, whereas grass monocultures yielded only 1·2–2·0 t DM ha−1 and 25–46 kg ha−1 N. From 1992 to 1994 the annual mean total herbage yield of DM in the mixtures declined from 12·2 to 10·5 to 8·7 t ha−1, the white clover yield declined from 8·7 to 6·5 to 4·1 t ha−1 and the average clover content during the growing season declined from 71% to 61% to 46%, whereas the grass yield increased from 3·4 to 4·0 to 4·5 t ha−1. The N yield decreased from 507 to 406 to 265 kg N ha−1 and the apparent N fixation from 470 to 380 to 238 kg N ha−1. Nitrate leaching losses during the winters of 1992–93 and 1994–95 were highest under mixtures with cv. Alice, but did not exceed 10 kg N ha−1. The in vitro digestible organic matter (IVDOM) was generally higher in clover than in grass, particularly in the summer months. No differences in IVDOM were found among clover or grass varieties. The experiment will be continued to study clover persistence and the mechanisms that affect the grass/clover balance.

Varietal differences in perennial ryegrass for nitrogen use efficiency in leaf growth following defoliation: performance in flowing solution culture and its relationship to yield under simulated grazing in the field

Varietal differences in rates of NO3 uptake and remobilization of nitrogen (N) during a cycle of severe defoliation and regrowth were assessed in perennial ryegrass (Lolium perenne L.) varieties Ba11778, Aberelan, Talbot and Gator. Plants were grown in flowing solution culture for 34 days, prior to a 30 d treatment period, including 21 d of regrowth. Net uptake of NO3 was measured continuously from solutions maintained automatically at 10 mmol m-3NO3.15 N-labelled NO3 3 was supplied to the plants in situ for either 21 h immediately prior to defoliation, or for 7-11 days afterwards, to measure remobilization of N from roots and stubble into the regrowing leaves. The four varieties differed only slightly in total dry matter production over 30 d, but varied substantially in post-defoliation specific growth rate by the leaf fraction. Gator was the lowest ( 0.11 g g-1 d-1), Ba11778 the highest ( 0.15 g g-1 d-1) and Aberelan and Talbot intermediate in leaf regrowth rate. Varieties did not vary significantly in shoot: root dry weight ratio, but the rate of NO3 uptake per unit of leaf fresh weight during regrowth was 27% lower in Ba11778 than in Gator. Leaves of Ba11778 and Aberelan had a lower organic N concentration in the dry matter at the end of the regrowth period than Talbot, which, in turn, had a lower concentration than Gator. Varieties differed in amount of leaf dry matter produced per unit of N absorbed by the plants after defoliation, the values (g g-1 N) being Ba11778 (22.6 ), Aberelan (20.7), Talbot (18.3) and Gator (16.7). More N was remobilized from the roots than from the stubble after defoliation. There were no significant differences among varieties in the amount and rate of N remobilization following defoliation. In earlier field experiments employing frequent cutting to simulate grazing, Ba11778 and Aberelan yielded at least 10% more dry matter annually than Talbot which, in turn, outyielded the amenity variety Gator by a similar amount. Thus the present results are consistent with the hypothesis that the efficiency of N use in leaf growth is an important factor determining genetic variation in productivity under frequent defoliation in the field when the herbage produced consists primarily of leaf.

Useful variation in in vitro digestibility within perennial ryegrass

In vitro dry matter digestibility (DMD) and dry matter yield (DMY) of herbage from plots sown with three selected perennial ryegrass varieties with similar heading dates (Ba11778, Talbot and Gator) under a range of harvesting frequencies (2, 3, 4 and 5-weekly harvests) were compared over two harvest years (1994 and 1995). Varieties varied in mean percentage DMD over all harvests and harvesting frequencies by 3.4 and 3.5 units in 1994 and 1995 respectively. Varietal ranking in mean DMD over all harvests was the same under each harvesting frequency in both years: Ba11778 being the highest, Gator the lowest and Talbot intermediate. In 1995, Gator had a higher proportion of unsown species in the herbage than both Ba11778 and Talbot but this was only a minor factor contributing to the differences among the varieties in mean DMD over all harvests. Although varieties consistently ranked in the same order of mean DMD over all harvesting frequencies during 13 5-week periods, the range among varieties varied from less than 1 unit to 8.6 units. This range was greatest in mid-season of each year when mean DMD over all varieties was lowest. The minimum mean DMD over all harvesting frequencies during both years was 75.5%, 70.9% and 66.8% for Ba11778, Talbot and Gator respectively. The most digestible variety Ba11778 also had higher annual DMY than the other two varieties in both harvest years and under all four harvesting frequencies. These results indicate that there is sufficient useful genetic variation for DMD within perennial ryegrass to justify breeding for the trait and its routine assessment in official variety trials.

The effect of a high‐magnesium perennial ryegrass variety on the magnesium status of sheep

AbstractAn early‐heading variety of perennial ryegrass (Ramore) bred for high magnesium (Mg) content was compared with an early control variety (Frances) for its ability to increase Mg intake, Mg utilization and blood Mg concentration in sheep, and so reduce the incidence of hypomagnesaemic tetany. Swards of the two varieties were established and each was grazed by ewes suckling twin lambs from turn‐out to weaning and thereafter by dry ewes. In early and late season herbage from a proportion of each sward was cut daily and fed fresh to ewes housed indoors in metabolism crates.Under grazing conditions herbage from Ramore swards had, over the 1992 and 1993 grazing seasons, a higher Mg concentration than Frances (2.35 g kg−1 vs. 2.18 g kg−1; s.e.m. 0.019, P< 0.001). During the spring period there was a higher (P 0.001, s.e.m. 0.0074) Mg concentration in the blood of ewes grazing Ramore (0.854 m mol 1−l) swards compared with those grazing Frances (0.793 m mol 1 −1) whereas during the autumn period blood Mg concentrations were higher in ewes grazing Frances. Ewe and lamb liveweight gains, recorded in 1992 only, were higher on Ramore swards than on Frances swards, although the difference was not significant.Indoor feeding studies showed that Mg intake was significantly higher (P< 0.001, s.e.m. 0.026) in ewes offered Ramore (1.98 g d−1) herbage compared with those offered Frances (1.74 g d−1) herbage with no significant difference in dry‐matter intake between the two varieties. Apparent availability and retention of Mg were higher for animals fed Ramore during the spring feeding periods than those fed Frances, but during the autumn feeding periods the reverse was true. Under indoor feeding conditions, variety had no significant effect on blood Mg concentrations.It was concluded that under grazing conditions a high Mg variety could provide an effective means of reducing the incidence of hypomagnesaemic tetany.

Response of perennial ryegrass varieties to annual changes in sward management

AbstractThe effect of annually switching sward management between cutting regimes that simulated rotational grazing and those for forage conservation vs. maintaining a constant management regime was studied by testing for ranking‐order changes between six perennial ryegrass varieties.Total dry‐matter (DM) yields were found to change in response to an annual switch in management. When under a conservation management and switched in the next year to simulated grazing, all six varieties yielded more in that year than when they were maintained constantly under simulated grazing. Similarly, when under a simulated grazing management and switched in the next year to conservation, all six varieties yielded less than when maintained constantly under a conservation management. These yield differences were largely expressed in spring of the year following the management switch.Differences in the ranking order of varieties were observed between the constant sward management treatments and the alternating managements. However, in these changes in variety ranking, no variety was consistently favoured or disadvartaged by the annual switch in management. Therefore, no clear evidence was produced that an alternating management system had any consistent effect on variety ranking and the observed changes were possibly due to the normal year‐to‐year variation frequently recorded in variety performance trials.

Suspension culture performance in commercial varieties of perennial ryegrass (Lolium perenne L.)

Suspension culture performance in commercial varieties of perennial ryegrass was studied to assess the effect of variety on suspension culture response and plant regeneration. 179 suspension cultures were established from embryos of mature seeds of 21 varieties and one breeding population. Of these, 123 suspensions were morphogenic (21 varieties) and 66 suspensions (18 varieties) regenerated green plants. A number of suspension lines, originating from two different suspensions, retained the capacity for green plant formation for almost four years. Replicates performed with seed lots of different ages indicated that suspensions initiated from young seeds (1 year) were of better quality than suspensions initiated from older seeds (2–4 years). Varieties differed in their capacity to form morphogenic suspensions and suspensions capable of regenerating green plants, although the effect of variety was relatively small. It was concluded that responsive genotypes can be found within most varieties of Lolium perenne.

Independence of dry matter yield and leaf yield among perennial ryegrass varieties differing in seasonal yield distribution

AbstractFour varieties of perennial ryegrass (Lolium perenne L.), (Ba11316, Merlinda, Morgana and Talbot), with similar ear emergence dates but differing in seasonal yield distribution were compared over two harvest years (1992 and 1993) in a small plot trial employing six levels of fertilizer N (100 to 600kg Nha−1 year−1 applied monthly as split dressings). In each year, a conservation cut in May was followed by five further harvests at monthly intervals. Herbage samples from each of the twelve harvests were separated into leaf lamina and other tissues, and the yield of leaf lamina calculated. The percentage of flowering tillers was determined in May and July of each year, Ba11316 produced significantly more dry matter (DM) than the other three varieties at six of the twelve harvests, but its total DM yield over all twelve harvests was 5% less than Merlinda and 3% less than Morgana, owing to lower yields of reproductive growth in May of both years. Varieties also varied in mean leaf content of the herbage over all harvests, Ba11316 being 69 g kg−1 higher than that of Merlinda. Differences among the varieties in leaf content were primarily because of difference in proportion of flowering tillers, Ba 11316 having a lower proportion of flowering tillers than the other three varieties. However, the mean leaf content of the tetraploid Merlinda was significantly lower than that of Morgana although these two varieties had a similar mean percentage of flowering tillers. Despite its lower total DM yield, Bal 1316 produced 16% and 14% more leaf over the two harvest years than Merlinda and Morgana respectively. Total leaf yield of Talbot was significantly higher than that of Merlinda and Morgana, although Talbot had been developed twelve years earlier than the other two varieties.

Interactions between variety and the timing of conservation cuts on species balance in Lolium perenne-Trifolium repens swards

The effects of two periods of rest from grazing by sheep (either April-May or May-June) on the composition of swards of both an early-flowering (Aurora) and a late-flowering (Melle) perennial ryegrass variety grown with cither a small-leaved (Kent) or a medium-leaved (Milkanova) white clover variety are described. Compared with a continuously stocked treatment, the early rest period did not affect the mass of clover in the swards (expressed as a proportion of the total) but resulted in a subsequent decrease in its population density. The late rest period doubled clover mass in the swards at the time of cutting but did not affect the subsequent population density of clover. The magnitude of the change in mass during the late rest period depended on ryegrass variety, but not on clover variety. The adverse effect of the early rest period on the subsequent population density of clover was associated with the degree of shading experienced by clover laminae at the end of the rest period. Temperature may also have had an effect here as mean temperatures were cooler during the early rest period than during the late rest period. It is concluded that the effects of the two rest periods on the clover content of the swards were primarily due to timing, and less to inherent differences between ryegrass varieties.

Seasonal variation in growth characteristics of Lolium perenne and Trifolium repens in swards under different managements

AbstractIn a range of perennial ryegrass/white clover swards, variation in the surface heights of the grass and clover components, the rates of increase of these surface heights and the specific leaf areas (SLAs) of ryegrass and white clover were described for 1 year. The swards were of an early‐ or late‐flowering (Aurora or Melle respectively) perennial ryegrass variety growing with either a small‐ or a medium‐leaved (Kent or Milkanova) white clover and were either continuously stocked by sheep or continuously stocked apart from a rest period in April‐May (Aurora) or May‐June (Melle).The surface heights of grass and clover were not affected by the variety of their companion species, and the surface heights of the two clover varieties were similar. The grass was always taller than the clover, although the magnitude of the difference between the species varied with time of year and the timing of the rest period.Before the summer solstice the rate of increase in height of grass was greater than that of clover except at cool temperatures (5°C) and warm temperatures (16°C), and in the unrested Melle sward. After the solstice the rates of increase in height, particularly of clover, were lower than the rates seen at similar temperatures before the solstice.Overall, the SLAs of both clover varieties were greater than those of ryegrass when grown with Aurora but not when grown with Melle, and the SLAs of both species increased during the year. By October the SLAs of both grass varieties were less than those of their companion clovers.The results are discussed in relation to their implications for the species composition of the swards.

The Relationship Between Progeny Seed Yield in Drilled Plots and Maternal Spaced‐Plant Traits in Perennial Ryegrass (Lolium perenne L.)

AbstractSeed production in perennial ryegrass, Lolium perenne L., is low. Early selection for high seed yield carried out in spaced plants would be valuable for breeders, but only if this potential is also expressed in derived progenies sown later in drilled plots. Therefore, spaced‐plant traits assessed on clonal ramets of 31 genotypes in each of two perennial ryegrass varieties in four environments were related to seed production characteristics in drilled plots of open‐pollinated progenies of these plants.Significant differences were found among these half‐sib families for seed yield, thousand‐grain weight, spring performance and earliness. The number of spikelets per ear in the maternal plants was negatively correlated with the seed yield of the progenies, explaining 17 % of the variation for seed yield in the cv. ‘Barenza’ and 14 % in the cv. ‘Wendy’. Multiple regression analyses revealed that no combinations of plant traits consistently explained a major portion of the variation for seed yield of the progenies.The results indicate that in these varieties, spaced‐plant data are of limited value in predicting seed production. Direct selection for seed yield in drills of progenies in later stages of the breeding programme remains the best method for obtaining varieties with sufficient seed production.

Breeding for management adaptation in perennial ryegrass (Lolium perenne L). I. Assessment of yield under contrasting cutting frequencies and relationships with leaf morphogenesis components

Summary — The potential yield under contrasting cutting frequencies was assessed among 18 diploid or tetraploid varieties of perennial ryegrass and 53 half-sibs progenies from a broad-based polycross. Simultaneously, a survey of the genetic variability of leaf morphogenesis components was carried out among the varieties. Both among varieties and progenies, the yield appeared to be negatively correlated between cutting frequencies and, compared with progenies, varieties were generally found to be more productive under infrequent cutting than under frequent cutting. Diploid and tetraploid varieties were discriminated only by morphogenetic traits related to tiller size and leaf elongation, as expected, with some association with the yield under frequent cutting and tiller density in the plots under the same management. The results suggested that there was a potentially high productivity under frequent cutting which should be considered but seemed to be systematically counterselected by plant breeders, probably due to the procedure of assessment of varieties for registration.

White clover contribution to continuously stocked sheep pastures in association with contrasting perennial ryegrasses

AbstractWhite clover content and herbage production in grass/clover swards were studied at contrasting altitudes in Wales. The lowland experiment (1) compared the performance of three clover varieties grown with four diploid perennial ryegrass (Lolium perenne) varieties with a range of heading dates. In the upland experiment (2) the productivity and persistence of Aberystwyth S184 (small‐leaved) clover was studied in association with three perennial ryegrasses.In experiment I. clover content and dry matter production with Aurora (very early) ryegrass was superior to that with Frances (early), Talbot (intermediate) and Melle (late). Furthermore, the performance of Kent wild white clover (small‐leaved) was better than that of medium‐leaved Menna and Grasslands Huia. Averaged over two years (1985 and 1986) mean clover content of Kent was 22% compared with 9% and 10% of Menna and Huia.Performance of S184 clover during the five years (1986–90) of experiment 2 was better with Meltra (late tetraploid) than with Aberystwyth S23 (late diploid) and intermediate with Aurora. Clover stolon length and growing point number declined to a low level in 1988 but increased dramatically in 1989 and 1990 after cessation of applying fertilizer N.Results from both sites were related to animal performance data previously published. It is concluded that small‐leaved clover varieties are needed to ensure a high proportion of clover in sheep pastures and also that choice of companion ryegrass can have a significant effect on the performance of the legume component.

Transient and stable expression of gusA fusions with rice genes in rice, barley and perennial ryegrass.

Transcriptional and translational fusions were made between the reading frame coding for beta-D-glucuronidase and sequences of either a constitutively expressed rice gene (GOS2) involved in initiation of translation or a light-inducible rice gene (GOS5). The transient expression of the fusions was studied via particle bombardment of seedling tissues of rice, perennial ryegrass and barley. Furthermore, the results of transient and stable expression were compared for cell suspensions of four rice varieties, one barley variety and one perennial ryegrass variety. The GOS2-gusA fusions were active in all three monocots studied. Best results were obtained for a construct having both a transcriptional and a translational fusion as well as intron and exon sequences (PORCEHyg). The level of GUS activity was in the range of activities as obtained by the 35S CaMV promoter transcriptionally fused to gusA. The gusA fusion with the light-inducible gene (GOS5) was active in green seedling tissues of all monocots studied. Also a weak expression compared to the GOS2 constructs was found in stably transformed rice callus. The gusA fusions with the mannopine synthase promoters 1' and 2' of the TR-DNA were transiently expressed at lower levels in cell suspensions than PORCEHyg. For stably transformed rice callus the expression of the GOS2-gusA fusion often decreased during prolonged subculture. This decrease in GUS activity and the various GUS-staining phenotypes of transgenic calli are explained by the presence of different cell types in the suspensions used and in the calli. It is presumed that the nature of the cells and their relative contribution in the calli change drastically upon further subculture.