165 research outputs found

    Application of Molecular Markers Derived from \u3cem\u3eMedicago Truncatula\u3c/em\u3e in White Clover (\u3cem\u3eTrifolium Repens\u3c/em\u3e L.)

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    White clover is the major forage legume of temperate areas. Genome maps have been produced recently (Jones et al., 2003; Barrett et al., 2004) and the location of QTL for important agricultural traits reported (Abberton et al., 2004). White clover is closely related to the model legume Medicago truncatula and there is likely to be considerable benefit in applying genomic resources from model to crop. However, the extent of synteny between the species must be established. Here we present preliminary results detailing progress towards this goal

    Breeding White Clover With Improved Tolerance of Nitrogen Fertiliser

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    White clover (Trifolium repens L.) is often considered a forage legume with a primary use in \u27low input/ low output\u27 systems. One facet of this is the perception that the persistency of this species is poor when Nitrogen (N) fertiliser is applied. However, new varieties of white clover are able to play a significant role in highly productive systems (Williams et al., 2000) and show consistent yields over ten years at a range of applied N levels (Williams et al., 2003). Germplasm improvement for nitrogen tolerance has been carried out with the aim of not only allowing white clover to perform well under applied N but also to dampen the oscillations in clover yield that may be a consequence of the build up of N fixed by the clover itself. The former aspect is illustrated in this paper with respect to the variety AberConcord

    Grass and Forage Improvement: Temperate Forages

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    Key points 1. Plant breeding has contributed significantly to the development of effective grassland production systems. 2. New technologies offer enhanced precision in breeding and access to wider genetic variation. 3. The requirement for more sustainable production systems will require genetic improvements in complex traits where the use of new technology will be vital

    Changes in Gene Expression During Acclimation to Cold Temperatures in White Clover (\u3cem\u3eTrifolium Repens\u3c/em\u3e L.)

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    White clover is an important component of many temperate pastures and improved winter hardiness is a major objective of breeding programmes in many countries. Exposure to cold and fluctuations in temperature are components of winter stress and although some studies have investigated the agronomic and physiological mechanisms of cold tolerance, little research has been carried out to identify the genes involved. We are complementing mapping of quantitative trait loci (QTL) responsible for cold tolerance with studies of variation in gene expression between plants growing at different temperatures. In particular we are initially focusing on the process of acclimation by analysing plants subjected to low but above zero temperatures

    Towards a Comparative Map of White Clover (Trifolium Repens) and Barrel Medic (Medicago Truncatula)

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    Grassland is of pivotal importance to the Irish agricultural industry. This dependence of grass is reflected in the large proportion of land area under grass, approx. 80% of the total land acreage in Ireland. The presence of white clover (Trifolium repens L.) in grassland significantly improves the overall nutritional value of the forage by increasing the relative amounts of nitrogen present. Genetic improvement of white clover through breeding of varieties should increase the productivity of grasslands. Advances in plant biotechnology offer the possibility of developing tools that will radically enhance our ability to breed improved plant varieties. The objective of this study is (1) to construct a genetic map of white clover and (2) to assess the level of genome synteny of white clover and M. truncatula (the model for legume species) with the use of different molecular markers developed in M. truncatula

    Grass and Forage Improvement: Temperate Forages

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    Plant breeding has contributed significantly to the development of effective grassland production systems. New technologies offer enhanced precision in breeding and access to wider genetic variation. The requirement for more sustainable production systems will require genetic improvements in complex traits where the use of new technology will be vital

    Root Senescence in Red Clover (\u3cem\u3eTrifolium Pratense\u3c/em\u3e L.)

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    Legume root systems form a mosaic of living, ageing and dead roots and nodules. The balance between these stages alters during plant development. Stressful events (drought, temperature change, reduced carbon supply, etc.) disturb the balance (Butler et al., 1959). Effects of root and nodule death on soil structure, composition and leaching and on plant persistency are understood poorly. Plants with differing senescence patterns are useful tools to study these effects. Molecular studies of root senescence need detailed knowledge of the process and timing of root senescence and death. Biochemical and histochemical markers of senescence were used to generate preliminary results of the effects of reduced carbon input, temporary (by defoliation, D) or permanent (by defoliation and shading, DS) on red clover shoot survival and root death

    Evaluation of a White Clover Variety With Increased Resistance to Stem Nematode (\u3cem\u3eDitylenchus Dipsaci\u3c/em\u3e) Under Sheep Grazing and Cutting

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    Stem nematode (Ditylenchus dipsaci (Kühn) Filipjev) is a major pest of white clover (Trifolium repens L.) in UK pastures (Cook et al., 1992a) and in other parts of the world. In a previous trial, resistant and susceptible selections yielded the same in three years in the absence of the nematode but, on infested plots, the susceptible yielded the same as the resistant selection in year 1 but only 68 and 58% in years 2 and 3, as the nematode infestation increased (Cook et al., 1992b). We have now developed varieties with enhanced resistance to this pest by screening under controlled conditions (Plowright et al., 2002). We describe an experiment to test the hypothesis that stress imposed on the plant by grazing as opposed to cutting management would exacerbate the effects of nematode infestation and accentuate the advantages of resistance through longer survival of clover plants

    Drought Tolerance of Interspecific Hybrids between \u3ci\u3eTrifolium repens\u3c/i\u3e and \u3ci\u3eTrifolium ambiguum\u3c/i\u3e

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    Hybrids between the stolonifeous white clover (Trifolium repens L., 2n=4x=32) and rhizomatous Caucasian clover (T. ambiguum M.Bieb, 2n=4x=32) have been produced. A backcross 2 (BC2) generation with white clover as the recurrent parent combines the growth habit of both parent species with the objective of increasing the persistency of large leaved T. repens varieties under grazing. T. ambiguum is more drought tolerant than T. repens. The drought tolerance of the hybrids in comparison with the parental species was compared in deep soil bins over a four week drought cycle. Soil moisture content, leaf relative water content (RWC), and leaf water potential were measured on plants subjected to drought and those watered normally and maintained at field capacity. T. ambiguum and the backcross hybrids were able to maintain a higher leaf RWC and leaf water potential than T. repens at comparable levels of soil moisture. The dry matter production of the hybrids and parental species was also compared in field plots sown with a perennial ryegrass companion. In the first harvest year, under a cutting regime, the yield of T. repens was highest and T. ambiguum lowest with the hybrids intermediate between the parents, with the BC2 approaching the yield of T. repens. These hybrids will be evaluated over further years and under grazing. The implications of these results for T. repens germplasm improvement programmes are discussed

    Quantifying the Variation in Protein Content in White Clover (\u3cem\u3eTrifolium Repens\u3c/em\u3e L.)

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    White clover (Trifolium repens L.) is the main legume in temperate pastures. It has relatively low levels of water-soluble carbohydrate but produces forage of high quality with a high crude protein (CP) content and dry-matter digestibility (Beever, 1993). Some studies have suggested that the forage quality of white clover can be problematic because its high CP content may contribute to inefficient use of nitrogen in the rumen and exacerbate diffuse pollution via excreta (Waghorn & Caradus, 1994). The development of white clover germplasm with lower CP content would potentially benefit forage production and grassland management. A study was carried out to quantify the variation in CP content within an existing gene pool and develop high throughput techniques for protein determination appropriate to a plant breeding programme
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