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1.
Inbred lines of white clover (Trifolium repens L.) have been produced utilising the rare self-fertility (Sf) allele. Twenty-two
lines of four distinct groups have been maintained through five generations of selfing by single seed descent. Fourteen lines
were used in crosses to produce F1s. Both parents and hybrids were analysed for a range of morphological characters. Positive heterosis for dry matter production
was observed in half the hybrids. No other trait showed significant heterosis. The degree of heterosis appears to be related
to the extent of variation in morphological characters between the parental lines, some combinations of lines yielding heterotic
hybrids in all cases, others in none. The majority of the F1 hybrids are superior in terms of dry matter production to eight control varieties.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
A.H. Marshall T.P.T. Michaelson-Yeates M.T. Abberton A. Williams H.G. Powell 《Euphytica》2002,126(2):195-201
Interspecific hybridisation with Trifolium nigrescens Viv. is a possible strategy to improve the reproductive potential of white clover (Trifolium repens L.). Following the development of a fertile F1 hybrid, three generations of backcrossing have been carried out usingT. repens as the recurrent parent. Vegetative characteristics, stolon growth and seed yield components of the backcross (BC) 2 and
3 generations, as well as the parental species were measured on spaced plants grown in the field. Leaf size and plant spread
of the BC2 and BC3 generations were less than T. repens but there was no difference in plant fresh weight. Numbers of inflorescences per plant and florets per inflorescence of the
backcrosses were greater than T. repens however this was not reflected indifferences in seed yield per plant asT. repens had more seeds per floret and per plant than the backcrosses. Differences in stolon length, the proportion of flowering nodes
and the pattern of axillary bud development were observed between T. repens and the backcrosses. Significant variation among the BC 3 generation for vegetative and reproductive traits was observed.
Individual plants among the BC 3 generation were identified that combine high forage yield, substantial inflorescence production
and good fertility, and these will form the basis of further selection.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
Winters AL Minchin FR Michaelson-Yeates TP Lee MR Morris P 《Journal of agricultural and food chemistry》2008,56(8):2817-2824
Polyphenol oxidase (PPO) activity in leaf extracts of wild type (WT) red clover and a mutant line expressing greatly reduced levels of PPO (LP red clover) has been characterized. Both latent and active forms of PPO were present, with the latent being the predominant form. PPO enzyme and substrate (phaselic acid) levels fluctuated over a growing season and were not correlated. Protease activation of latent PPO was demonstrated; however, the rate was too low to have an immediate effect following extraction. A novel, more rapid PPO activation mechanism by the enzyme's own substrate was identified. Rates of protein breakdown and amino acid release were significantly higher in LP red clover extracts compared with WT extracts, with 20 versus 6% breakdown of total protein and 1.9 versus 0.4 mg/g FW of free amino acids released over 24 h, respectively. Inclusion of ascorbic acid increased the extent of protein breakdown. Free phenol content decreased during a 24 h incubation of WT red clover extracts, whereas protein-bound phenol increased and high molecular weight protein species were formed. Inhibition of proteolysis occurred during wilting and ensilage of WT compared with LP forage (1.9 vs 5 and 17 vs 21 g/kg of DM free amino acids for 24 h wilted forage and 90 day silage, respectively). This study shows that whereas constitutive red clover PPO occurs predominantly in the latent form, this fraction can contribute to reducing protein breakdown in crude extracts and during ensilage. 相似文献
4.
Toby A. Joyce Michael T. Abberton T.P.T. Michaelson-Yeates John W. Forster 《Euphytica》1999,107(3):159-165
The RAPD-PCR technique has been used to generate DNA amplification profiles from a set of advanced generation inbred lines
of white clover ( Trifolium repens L.). The genetic distances between lines have been estimated and have been compared with
the extent of positive heterosis for dry matter yield in hybrid crosses. The analysis clearly separated the four major groups
(H, J, R and S), with little within group variation. Heterosis, previously shown to be positively correlated with the extent
of phenotypic variation between parental lines, was greatest between lines from groups showing the least genetic distance.
The lack of correlation between heterosis and genetic divergence is discussed in the context of results from other systems.
Additionally, the data allow a comparison of the extent of phenotypic variation for a trait under selective pressure with
the degree of variation at the DNA level detected with the RAPD technique.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
Nitrogen Fixation by Hybrids of White Clover (Trifolium repens L.) and Trifolium nigrescens 总被引：1，自引：0，他引：1
M. T. Abberton J. H. MacDuff A. H. Marshall T. P. T. Michaelson-Yeates 《Journal of Agronomy and Crop Science》1999,183(1):27-33
Development of hybrids between white clover ( Trifolium repens L.) and Trifolium nigrescens provides a novel route for genetically improving the reproductive capacity of white clover, provided the hybrids are agronomically viable, particularly with respect to N2 fixation. A comparative study of growth and rates of N2 fixation over 21 days was conducted with the parental species, F 1 hybrids and backcross hybrids, in flowing solution culture, without a supply of mineral N to the plants. T. nigrescens was unable to fix N2 in association with the strains of Rhizobium leguminosarum biovar. trifolii selected for inoculation. Rates of N2 fixation per plant increased in the order T. nigrescens < F 1 hybrid < T. repens < backcross 1. Specific rates of N2 fixation (days 0–21) increased in the order T. nigrescens < F 1 hybrid < backcross 1 < T. repens . Dry matter production and nodule biomass per plant increased at a higher rate in backcross 1 hybrids than in T. repens. The results suggest that the potential for N2 fixation by backcross 1 hybrids is at least as great as that by T. repens . 相似文献
6.
A. H. Marshall T. A. Williams M. T. Abberton T. P. T. Michaelson-Yeates P. Olyott H. G. Powell 《Grass and Forage Science》2004,59(1):91-99
Interspecific hybrids between white clover (Trifolium repens L.) and Caucasian clover (Trifolium ambiguum M. Bieb.) have been developed to introgress the rhizomatous growth habit into white clover, to increase persistence and drought tolerance. The forage quality of T. repens, T. ambiguum and the backcross 1 (BC1) and backcross 2 (BC2) hybrids and companion grass, when grown in mixtures with an intermediate perennial ryegrass (Lolium perenne L.) under a cutting‐only management, was measured. In vitro dry‐matter digestibility (DMD), water‐soluble carbohydrate (WSC) and crude protein (CP) concentrations of the legume and grass fractions were measured throughout the growing season over three harvest years. Trifolium repens had a lower WSC but a higher CP concentration than the perennial ryegrass companion in all harvest years and at all cuts. The legume fractions from the BC1 and BC2 hybrid plots had a higher WSC and a lower CP concentration but an in vitro DMD value comparable with white clover throughout the growing season and in each harvest year. The grass fractions from the mixtures with the backcross hybrids had a higher WSC and a lower CP concentration than the grass fraction from the T. repens plots, in all harvest years and throughout the growing season. No difference in in vitro DMD between parental species and backcross hybrids was observed. The implications of these results for the development of these hybrids and animal performance are discussed. 相似文献
7.
Nitrogen Fixation in Hybrids of White Clover (Trifolium repens L.) and Caucasian Clover (Trifolium ambiguum M. Bieb) 总被引：2，自引：0，他引：2
M. T. Abberton J. H. MacDuff S. Vagg A. H. Marshall T. P. T. Michaelson-Yeates 《Journal of Agronomy and Crop Science》2000,185(4):241-247
Hybrids between white clover (Trifolium repens L.) and Caucasian clover (or Kura clover, Trifolium ambiguum M. Bieb) are a potential route for the improvement of drought tolerance and persistence in white clover. However, to be agronomically viable they must show no significant reduction in their potential for nitrogen fixation relative to white clover. A comparative study of growth rate and nitrogen fixation was carried out in flowing solution culture without a supply of mineral nitrogen to the plants. The two parental species and two generations of backcross hybrids, with white clover as the recurrent parent, were assessed. The growth rate and N content of T. ambiguum were significantly lower than those of the other lines. However, dry matter production, nodule biomass per plant and rates of fixation were similar in second‐generation backcross plants and white clover. The results suggest that the agronomic potential of this novel germplasm is not compromised by limitations with respect to nitrogen fixation. 相似文献
8.
A diallel cross amongst four contrasting white clover varieties was used to provide genetic information on those characters which affect the productivity of white clover-perennial ryegrass mixtures when grown under a cutting-only management regime. Generally speaking those characters recorded on the clover families and in mixtures exhibited highly significant additive and non-ad dative genetic effects, though for1 sortie characters the latter could not be ascribed solely to dominance effects. For two of the clover characters, stolon and leaf number, the genetic picture was radically altered in mixtures by the effects of inter-specific competition Pseudo-genetic effects were also detected for the grass characters, bur it was suggested that the two ryegrass varieties used here were exhibiting phenotypic plasticity. As a group the four intra-varietal crosses performed significantly better than the six intra-varietal crosses for all clover and mixture characters. Only one of the inter-varietal crosses had significantly positive specific combining ability effects for most characters and that was between the two long established varieties ‘S. 184’ and ‘S. 100’. The implications of these results for the breeding of white clover varieties for use in mixtures are briefly discussed. 相似文献
9.
Growth, dry matter partitioning between shoots and roots, and extent of nodulation were characterised in four novel self-fertile
highly inbred lines (referred to as A, B, C and D) of white clover (Trifolium repens L.) thought to differ fundamentally in
their nitrogen relations and therefore regarded as candidate material for genetic mapping. Plants were inoculated with a mixture
of three strains of Rhizobium and grown in flowing nutrient solutions without N for 18 d. Half the plants were then supplied
with 20 μM NO3
- during a 36 d treatment period, the remaining plants acting as ‘controls’ solely dependent upon N2 fixation for acquisition of N. Total dry matter production and shoot:root ratios were similar in all lines supplied with
NO3
- and in control plants of lines B and C. Growth was severely reduced in control plants of line D and to a lesser extent in
control line A. These effects were attributed to a failure to develop effective N2 fixation capacity after apparently normal infection. Mean nodule size, nodule numbers and nodule d.w. per plant were extremely
low in line D compared with the other lines, irrespective of whether NO3
- was supplied. Lines A, B and C differed in the severity with which NO3
- decreased mean d.w. per nodule and total nodule d.w. per plant relative to corresponding control plants, with line C being
least sensitive. Nitrate also decreased the total number of nodules per plant relative to control plants after day 14 in all
lines except C, and most severely in line B.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
10.
A diallel crossing programme amongst tour contrasting white clover varieties was used to generate material for studying the interrelationships amongst those characters which affect the productivity of white clover- perennial ryegrass mixtures under a cutting-only management regime. Such a regime favoured clover growth. All the clover characters exhibited strong positive correlations with mixture yield. However, this combination of clover characters did not promote growth of the grass companion. For this a low growing variety with a dense stolon network appeared preferable. Path analysis indicated that differences existed between the two companion grass varieties used for this experiment in their upon clover characters. 相似文献