Plant lipids are a major source of beneficial fatty acids (FA) in milk. Forage quality differences can affect rumen metabolism and there could be opportunities to change the composition of ruminant products through species or cultivar choice. Twelve dairy cows were used in two stall-feeding trials with fresh grass to evaluate the effect of diploid perennial ryegrass (Lolium perenne) cultivars on milk FA composition during the growing season. Six cultivars were cut daily during three 14-day periods at the same target yield. The experiments consisted of two 3x3 Latin square trials, in each of which 3 cultivars were fed to 2 groups of three cows. The six cultivars differed significantly in concentrations of water-soluble carbohydrates, neutral-detergent fibre and crude protein. However, there were no significant differences among the six cultivars in FA concentration or proportions of FA. No variation in DM intake, milk production and composition or milk FA composition was found. The latter may be due to the lack of variation in grass FA concentration and composition in the cultivars studied.
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(312 KB)Cereal forages provide both arable and livestock farmers with high yields of high quality dry matter to use as either standing or conserved strategic forage supplements where deficits occur when animal feed requirements exceed pasture growth. Crop & Food Research has breeding programmes for both single and multigrazing forage oats and triticales, and both green-chop and whole-crop silage forage oats, triticales and barleys. It also has an associated cereal forage management research and tech-transfer programme to ensure cereal forages achieve their potential under New Zealand’s variable soil and climatic conditions. This has led to the development of new cereal forage cultivars, an increased understanding of their dry matter and quality development, and management support packages including a cereal silage booklet and maturity predictor for whole-crop cereal silage
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(336 KB)The use of DNA markers to accelerate genetic improvement of forages presents a unique set of opportunities, challenges, and benefits. Our experiments in full-sib mapping populations of white clover and perennial ryegrass have detected >75 quantitative trait loci (QTLs), each with multiple marker:trait associations at specific locations in either the perennial ryegrass or white clover genome. A subset of these QTL are robust (detected in multiple years / sites / populations) and exert a substantial influence on performance, warranting exploration of development for application in Marker-assisted Selection (MAS) breeding programmes. Ryegrass QTLs associated with herbage yield, seed yield, plant size and habit, cold tolerance, seasonal regrowth, and disease have been identified, whereas QTL discovery in white clover has been focused on reproductive traits. Markers from two white clover QTLs were used to develop marker assays suitable for selection of parental plants with superior breeding value for seed yield potential. Tandem testing of the two assays over two field seasons and eight populations indicates that substantial change in seed yield may be achieved (up to 90% increase), and that the marker / allele / phase relationships to plant performance are population specific. These data point to an opportunity to develop selection tools on a population specific basis, and to a challenge to implement MAS approaches tailored for open-pollinated population breeding systems.
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(324 KB)New genes for ‘sustainability’ traits are being incorporated into ryegrass (Lolium sp.) breeding populations using marker-assisted intra- and inter- specific introgession from a wide range of genetic resources. Mapping families, substitution and introgression lines have been produced to facilitate gene transfer between Festuca and Lolium species. Advanced metabolomic phenotyping techniques (e.g. NIRS and FT-IR) can help close genotype-phenotype gaps to increase the environmental sustainability of grassland and improve the nutritional value of genotypes for forage or their chemical suitability for biofermentation/biofuel.
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(353 KB)Pastoral Genomics is engaged in applying molecular mapping and functional genomics to characterise and manipulate key phenotypic traits associated with improved productivity in the commercially important forage crop white clover (Trifolium repens L.). We report on the development of a framework linkage map for white clover and the application of this map to the identification of quantitative trait loci (QTL) associated with vegetative and seed yield traits. Homologues of genes responsible for the traits of interest have been identified and cloned in order to identify ‘perfect markers’ for marker assisted breeding and to develop a cisgenic® clover cultivar. We introduce western clover (T. occidentale), a diploid perennial clover species closely related to white clover, as a stoloniferous clover model to dissect low heritability traits initially intractable in white clover. We have identified extensive genetic variation in this species, which previously has been reported to be remarkably uniform. We have developed a framework map for T. occidentale and demonstrated conservation of marker order and spacing with white clover. An ethyl methane sulfonate (EMS) mutant population has been used to isolate three distinct groups of condensed tannin (CT) mutants. We have also investigated our model’s transformation potential, achieving frequencies 2-3 fold higher than for white clover and suggest that this model is potentially useful for genomic analysis of white clover and other clonal species
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(310 KB)A number of recent reports in New Zealand have stated that restricted access to new plant genetic material from overseas is a major risk to the future growth of the primary sector. This paper reviews one part of the overall problem by discussing the historical role of exotic forage germplasm in plant improvement in New Zealand, and quantifies the current contribution of recently imported plant material to exports from the pastoral sector. In the past 30 years there has been a large increase in the number of improved cultivars. There are now 115 forage cultivars of 26 species available to farmers, compared with 20 cultivars and 12 species in the early 1970s. 65 per cent of these contain exotic germplasm. The current annual contribution of cultivars containing exotic forage germplasm to New Zealand pastoral exports of around $14 billion is $735 million. This represents an almost 6 fold increase over the figure of $128 million in 1992, which is significantly faster than the 75% increase in pastoral exports in the same period. A more important issue is the loss of future opportunities which will result from the continuation of restricted access to novel material from overseas. These include responses to climate change, biosecurity breaches and developments in biotechnology, food type and quality and endophyte. A return to the well tried system of accredited institutions carrying out field evaluations under supervision is proposed.
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(322 KB)
We have studied metabolic and gene expression responses of two white clover genotypes differing in foliar basal flavonol and anthocyanin levels subjected to moderate cold in a controlled climate chamber experiment. The main flavonols and anthocyanins accumulating in white clover leaves are conjugated to galactose and xylose. Concentrations of flavonoids and sugars including starch significantly increased during cold treatment and a strong induction of flavonoid pathway genes was observed in both genotypes. Specific sugars like glucose, fructose, and starch were significantly higher in the genotype with low basal flavonoid levels. By combining metabolic and gene expression analysis we have identified two genes probably involved in the conjugation and deconjugation of flavonoids, a flavonoid galactosyltransferase and a β- galactosidase. The selected flavonoid galactosyltransferase was up-regulated by cold treatment and was also expressed at higher levels in the red leaved genotype. The β- galactosidase studied here was down-regulated by cold and expressed less in the red leaved genotype. These results indicate a tight link between primary and secondary metabolism in clover and demonstrate the value of combined metabolome and transcriptome analysis for the identification of specific gene functions.
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(408 KB)Anthers from 32 genotypes from one line of annual ryegrass (Lolium multiflorum) and 229 genotypes from 15 cultivars of perennial ryegrass (L. perenne) were tested for the production of haploids and double haploids. Six (23%) annual and 71 (31%) perennial ryegrass genotypes produced calli ranging from 1.3-16% and 0.8- 12.2% respectively. However none of the annual ryegrass genotypes produced green plants and only one genotype (Option WH-1) of perennial ryegrass produced 16 (1.8%) green plants. The remaining produced only albino regenerates. Twelve of the 16 green plants were evaluated cytologically for chromosome numbers. Four were haploids thus confirming their origin from haploid pollen. The remaining eight were all diploids. One haploid and one diploid were tested for their homozygous condition using seven simple sequence repeat (SSR) markers and were found to be homozygous at all seven loci. In order to increase the recovery of green regenerates, we have used the responsive genotype Option WH-1 in crosses with three other perennial ryegrass genotypes and the progenies are currently been grown for anther culture
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(350 KB)Lolium perenne (ryegrass) is the most widely sown pasture grass in New Zealand providing forage for millions of sheep and cattle. Genetic improvement of Lolium species through conventional breeding has been particularly difficult because of its outbreeding and heterozygous nature. Biotechnology techniques that are not based on genetic modification technology, such as protoplast fusion, could help in the breeding of L. perenne as it enables the introgression of DNA (and associated desirable traits) from other species of plants that are otherwise unobtainable by conventional means. We intend to adapt this technology for L. perenne and report on our progress with the isolation of protoplasts, micro colony and callus formation, and shoot regeneration. Friable callus was induced from L. perenne seeds and used for isolation of protoplasts. After testing several combinations of enzyme mixtures at different molarities, a high yield of protoplasts (1.1 × 107 g-1 FW) with a viability of 82% has been obtained. Callus colonies were formed from protoplasts cultured on a nitrocellulose membrane over a feeder layer. Plating efficiencies of 0.1-0.2% were obtained. Regeneration of plantlets from these colonies were obtained on Linsmaier and Skoog medium supplemented with growth hormones. All the plants regenerated to date have an albino appearance.
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(312 KB)The primary breeding objective for white clover improvement in eastern Australia is more reliable persistence under summer moisture-stress while maintaining herbage production (especially winter growth). To identify elite germplasm, evaluation of candidate lines is done in situ, under field conditions for which the prospective cultivar is targeted. These conditions (e.g. moisture stress, nutrient infertility, grass competition) may impose spatial influences within the field site that as artefacts mask or alter the uniform expression of response to environment. A significant component of artefact variation which affects interpretation of the data is the spatial variation due to plot position. Failure to correct for this may give unreliable comparisons as some lines inadvertently (through randomisation) are allocated to favourable or unfavourable plots. Our methodology was developed at two sites (Glen Innes , Armidale in northern New South Wales, Australia) in an experiment which sought to identify superior lines among 20 candidate entries. Cultivars of reputed stability and spanning the expected performance range, are replicated at regular intervals through the field site. The difference amongst replicates within cultivar (that is a reduced G X E) is used to estimate spatial trends. Elite lines are identified from temporal profiles of plant performance related to the breeding objectives. We describe (i) design and analysis which allows estimation of the spatial effects, and (ii) the temporal profiling of plant performance. These statistical procedures are seminal in identifying superior breeding lines that subsequently proceed to cultivar development.
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(479 KB)
A full-sib mapping population (n=188) from a cross between cultivars ‘Grasslands Impact’ and ‘Grasslands Samson’ was used to identify quantitative trait loci (QTL) controlling seed yield and component traits in perennial ryegrass. Thirteen traits, including seed yield per plant (SYP) and five seed yield components (number of spikes (SP), spikelets per spike (SS), florets per spikelet (FSP), seed weight (SW) and floret site utilisation (FSU)), seed yield per spike (SYH) and seven other seed yield-associated traits, were phenotypically assessed in a replicated spaced plant field experiment. Interval mapping identified 35 QTL for all traits but one, spanning all linkage groups (LG). Multiple QTL were detected for most traits. QTL for SYP and component traits, as well as some seed yield-associated traits, co-located to the same genomic regions on LG 1, 2 and 6. Markers associated with these regions, in particular, will form the basis for the on-going development of MAS tools for improvement of seed yield and quality in breeding programmes. Further development will require refinement of QTL positions and effects using multiple QTL mapping (MQM), and validation of QTL and associated markers in other genetic backgrounds and environments
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(410 KB)Perennial ryegrass is the key forage component in pasture systems in New Zealand, Australia and Europe, and is typically characterised by a shallow root system. Breeding for a deeper root profile is desirable, as root depth influences drought tolerance, anchoring of plants against removal by grazing animals, and nutrient capture. Difficulties associated with conventional selection for root traits may be alleviated by developing marker-assisted selection (MAS) tools, the first stage of which is the identification of quantitative trait loci (QTL). The objective here was to detect QTL influencing vertical root distribution in ryegrass. A root distribution ratio, RTD, was measured in a replicated mapping population (n=188) grown in sand-filled tubes. Six QTL for RTD were detected on five linkage groups, individually accounting for 4 – 18% of phenotypic variation in this trait. In silico comparative analysis indicated colinearity between ryegrass RTD QTL and QTL for root traits in the rice genome. To enrich marker density specifically at RTD QTL, comparative information was used to develop sequence-tagged site (STS) markers from rice genome-aligned ryegrass expressed sequence tags, with, thus far, STS markers ppt014 and ppt019 successfully targeted to QTL qRTD-3.2 and qRTD-6, respectively. This investigation represents the first step towards developing a MAS strategy for improved root distribution and, subsequently, perennial ryegrass cultivars with superior persistence and environmental performance.
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(399 KB)New Zealand perennial ryegrass germplasm originated largely from seed introduced from the UK during the 1800s. Modern breeding began in the 1930s and soon utilised selections from the best ecotypes as “mother” seed for the seed industry and after numerous reselections this resulted in the release of Grasslands Ruanui 1955. Winter growth was improved by hybridising with Italian ryegrass to produce the “short rotation hybrid” cultivar Grasslands Manawa, released in 1943. Further introgression to perennial ryegrass led to the development of Grasslands Ariki “long rotation hybrid”, functionally a perennial, released in 1965. The identification of a valuable ecotype from the Mangere district in Northern New Zealand in the late 1960s had a substantial impact on ryegrass breeding in New Zealand and has subsequently been widely used in all Australasian ryegrass breeding programs. Germplasm from mild oceanic regions of North West Spain, collected in the 1980s, has provided a valuable combination of winter growth with late flowering behaviour. This has been used in many recent breeding programs. Considerable research has gone into endophytes of ryegrass to develop safe and persistent pastures. The lack of chemical diversity within endophytes of New Zealand ecotypes has required considerable sourcing of overseas germplasm for endophyte discovery. In recent years breeders have introgressed a wider range of germplasm, including winter active Mediterranean material, cold tolerant Northern European material, as well as Italian ryegrass and meadow fescue. Tetraploid perennial ryegrass cultivars have been released in the last 20 years, based largely on New Zealand diploid cultivars but also using some European tetraploids. Today a full range of cultivars from early flowering diploids to late flowering tetraploids is available to the farming industry. The use of a wider range of germplasm is discussed in relation to advances in our knowledge of genetic origins of perennial ryegrass. Genetic advances should be achievable from more diverse germplasm by using a combination of traditional breeding techniques and new technologies, such as marker assisted selection. However, lifting overall pasture performance still remains a challenge as ryegrass cultivars are used in mixtures with white clover and any increase in the ryegrass yield is often partially cancelled by decreased clover yields
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(335 KB)Fifteen plants, replicated twice, of each of 20 half-sib families of perennial ryegrass were grown in deep sand tubes irrigated with a low ionic strength nutrient solution in a glasshouse. Top growth was measured. Roots were turned out, cut into 10 cm profile increments, washed free of sand, dried and weighed. For top growth, total root growth and root-shoot ratio, there were significant differences among families translating to narrow sense heritability coefficients between 0.3 and 0.4. However, the ratio between root in the top 10 cm and total root, and a parameter for a well-fitting exponential model describing root profile showed variation between individuals but very little or no variation between families. This translated to narrow sense heritability coefficients of less than 0.1.
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(309 KB)
Neotyphodium lolii is a fungal endophyte that lives entirely within the intercellular spaces of its grass host, perennial ryegrass (Lolium perenne L.). Infection is symptomless and the endophyte relies on the host plant for dissemination via the seed. The association is mutually beneficial since the endophyte confers a number of biotic and abiotic advantages to the host. This paper will present an overview of the multidisciplinary approach we are using at AgResearch to dissect the molecular basis of this symbiosis. Topics covered will include how we intend to link the knowledge gained from basic biology and cytology with the fields of Genomics, Transcriptomics, Proteomics and Metabolomics. To achieve this we are using isogenic ryegrass lines infected or uninfected with endophyte in combination with a suite of molecular biology tools, including Expressed Sequence Tags (ESTs), Microarray analysis, 2D-gel electrophoresis (to identify novel proteins associated with symbiosis), and metabolic profiling. To aid our proteomics approach, we have also generated both fungal genomic and fungal EST resources. By linking these approaches we hope to identify genes which are important in both the establishment and maintenance of symbiosis. In addition, by combining transcriptomic with metabolomic approaches, we intend to elucidate how endophyte infection influences host secondary metabolism. We hypothesise the latter is correlated with many of the endophyte-conferred enhancements to its host
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(527 KB)Neotyphodium endophytes usually confer resistance on their host grasses to insect attack, but can also occasionally increase host plant susceptibility to particular insects. In either case host plant genotype interaction with the endophyte appears to play a role in determining the strength of the interactions between the insect and its host. An example of this is the relationship between the root aphid, Aploneura lentisci and perennial ryegrass infected with different strains of endophyte. Aphid numbers on individual ryegrass plants infected with the Wild-type endophyte are generally similar to, or less than, those on endophyte-free (Nil) ryegrass whereas populations on plants infected with the AR1 endophyte are significantly higher. By analysing for differences between individual plants using data from five different samplings, significant differences in both the total number of root aphid per plant and aphid loading (number/g of root) were found among 20 plants infected with either the Wild-type or AR1 (P<0.01). Host plant genotype of Nil plants also significantly affected aphid numbers (P<0.05) but not aphid loading. Population growth of aphids subsequently showed a strong effect of plant genotype for AR1-infected plants but not for Nil plants. In a further trial using cloned plants from half-sibling families of both AR1 and Wild-type, there were significant family effects on aphid numbers/plant, suggesting heritable variation for host control and that selections could be made for AR1 plants that supported low numbers of this insect. There was no comparable variation amongst families infected with Wild-type endophyte in the same experiment
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(317 KB)Peramine concentrations in a range of ryegrass/ AR1 endophyte associations have been measured during pre-market safety testing. While concentrations for diploid perennial ryegrass cultivars were in excess of 15ppm a small number of associations were below 10ppm. These proved to be tetraploid ryegrass. When assessing the effectiveness of a ryegrass/AR1 association to deter ASW, and other invertebrate pasture pests, the host ryegrass cultivar or genotype and consequent peramine concentrations need to be taken into consideration.
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(314 KB)Italian ryegrass (Lolium multiflorum) and short-term hybrid ryegrass (L. boucheanum) have reliable establishment and high cool season growth, but varying persistence after the first summer. In Northland, there is increased stress on ryegrass from invertebrate insect attack. Selected strains of endophyte (Neotyphodium lolii) have been identified that protect perennial ryegrass from invertebrate attack. Two of these endophyte strains (AR1 and AR37) were inoculated into two Italian ryegrass cultivars (Status and Corvette) and compared in a small plot agronomic trial with the same cultivars free or low in the naturally-occurring endophyte N. occultans. From April 2004 to June 2005, ryegrass plots with these endophyte-cultivar combinations were measured for dry matter yields and plant survival under summer/autumn insect pressure in Northland. In autumn/winter 2005, novel endophytes resulted in greater plant survival and yield advantages (82%) than the same cultivars with no/low N. occultans endophyte. These effects were consistent across cultivars. Increased agronomic performance corresponded with lower damage from African black beetle larvae (Heteronychus arator). This result has implications for extending the persistence and potential yields of Italian/hybrid ryegrass pastures subject to pest attack.
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(319 KB)
In the colder parts of the United States, in late winter after disappearance of snow cover, red clover (Trifolium pratense) is often broadcast seeded into forage legume-depleted grass pastures to increase pasture forage quality. This method of establishment is referred to as frost seeding. However, in an estimated 30-40% of frostseeded pastures in Wisconsin, USA the legumes fail to establish. In this study 40 red clover halfsib families from one breeding population and six check populations were evaluated for spring 2005 establishment by 1) broadcast seeding into existing pasture under frost-seeded conditions and 2) standard drill seeding into 15 cm-spaced rows. In June 2005 seedling counts and heights were measured on halfsib family plots. Narrow sense heritability estimates on a halfsib family basis for seedling stand counts under frost- and drill-seeded establishment were h2 = 0.02 and 0.21 respectively. Heritabilities for seedling height under frost- and drill-seeded establishment were h2 = 0.50 and 0.26. Genetic correlations between seedling counts and heights under frost- and drill-seeded establishment were rA = 0.42 and 0.19 respectively. No significant genetic correlations between frost- and drill-seeded heights (rA = -0.09) or seedling counts (rA = 0.20) were detected. These results suggest that seedling performance in frost-seeded conditions is a distinct trait from seedling performance in standard drill-seeded conditions and that each needs a separate selection program.
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(411 KB)Determining the impact of inbreeding on white clover growth will assist in determining the optimal breeding strategies for future population improvement. A dominant self-fertility allele (Sf) at the S locus was used to inbreed white clover to nearhomozygosity (F=0.99). Inbreeding depression was higher in the glasshouse experiment than was observed under sheep grazing in the field. It was also higher for comparable generations with a 54% reduction in herbage yield of the S1 generation in the glasshouse compared with 29% yield reduction under grazing. The level of inbreeding depression for herbage yield of the S1 and S2 generations observed in the glasshouse were consistent with the theoretical reduction in yield. However in later generations the actual herbage yield was consistently higher than expected. This may be due to heterozygosity being maintained during inbreeding or to the elimination of weaker individuals under higher competition and grazing experienced under field conditions. The degree to which inbreeding depression is overcome by outcrossing (heterosis) in white clover will determine whether hybrids or semi-hybrid cultivars can be successfully developed
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(314 KB)The effect of leaf feeding by adult clover root weevils on the isoflavonoid content of red and white clovers was investigated in a glasshouse experiment. Lines of both clovers previously selected for variation in formononetin content were used. A higher percentage of white clover leaves than red clover leaves were damaged by the weevils, and the high formononetin red clover was least readily eaten. The formononetin content of the white clovers did not differ between the selections, was much lower than in the red clovers, and did not change in response to weevil feeding. In both red clover lines, formononetin and biochaninA levels rose in response to weevil feeding, suggesting that both compounds have antifeedant properties against clover root weevil. Because high foliar levels of oestrogenic compounds like formononetin threaten fertility of grazing sheep it is concluded that plant breeding programmes should increase the levels of formononetin and/or biochaninA in clover roots to mitigate the impact of weevil larval feeding on roots and nodules.
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(343 KB)Plant cuticular waxes play an important role in protecting aerial organs from damage caused by multiple environmental stresses such as drought, cold, UV radiation, pathogen infection, and insect attack. We characterized a novel AP2 domain-containing transcription factor gene, designated WXP1, from the model legume plant Medicago truncatula. The gene is able to activate wax production and confer drought tolerance in alfalfa (Medicago sativa). The predicted protein of WXP1 has 371 aa; it is one of the longest peptides of all the single AP2 domain proteins in M. truncatula. Transcript level of WXP1 is inducible by cold, ABA and drought treatment in shoot tissues. Overexpression of WXP1 under the control of CaMV35S promoter led to a significant increase in cuticular wax loading on leaves of transgenic alfalfa. Transgenic leaves showed reduced water loss and chlorophyll leaching. Transgenic alfalfa plants with increased cuticular waxes showed enhanced drought tolerance demonstrated by delayed wilting after watering was ceased and quicker and better recovery when the dehydrated plants were re-watered.
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(780 KB)White clover is used worldwide to improve the nutritive value of pastures and is an increasingly important component of environmentally-sustainable grassland ecosystems. In 1991, a white clover breeding program involving two New Zealand companies (AgResearch and Midlands Seed) and a European company (Barenbrug), was initiated to develop new varieties for agricultural systems in the United Kingdom. This collaborative international program has been very successful with three improved varieties, Crusader, Barblanca and Makuri, being released and listed in the United Kingdom. The improved persistence and productivity of these varieties has enabled them to secure a significant share of the UK proprietary seed market. In particular, the medium-leaved Crusader produces at least 30% more DM than any other small or medium-leaved white clovers in UK Recommended List trials. Changes in agricultural subsidies within the EU Common Agricultural Policy and the growing pressure to use environmentally sustainable agricultural practices should increase demand for new generation white clover varieties that can maximise both pasture production and animal productivity.
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(316 KB)Application of molecular marker technology to identify Quantitative Trait Loci (QTL) associated with key root traits is expected to enhance white clover breeding programmes, to improve characteristics such as increased efficiency in phosphorous (P) uptake and summer moisture stress tolerance. The phenotypic diversity for a range of root morphological traits among 500 mapping family (F1) progeny was characterised using plants grown hydroponically. The root traits measured were: dry weight, length, surface area, diameter, volume, numbers of root tips and root forks. Variance component analysis indicated significant (P<0.005) genotypic variance among the 500 progeny for all the root traits measured. For most root traits the differences between the minimum and maximum values also indicated a large range of phenotypic variation among the 500 progeny. Pattern analysis helped identify progeny groups as well as providing a graphical representation of the association among the root traits. One of the progeny groups contained members with root trait morphology indicating the potential to enhance soil penetration per unit volume of soil, which could result in improved soil P uptake. The genotype-by-root trait matrix of individual progeny means generated from this study will be used for preliminary QTL analysis.
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(388 KB)The clover root-knot nematode, Meloidogyne trifoliophila (Mt), debilitates white clover (Trifolium repens) in New Zealand pastures. Genetic resistance (R) to Mt in white clover is complexly inherited and difficult to utilise in breeding programmes. Single-gene, dominant, and complete R to Mt has been identified at the TRKR locus in T. semipilosum. The current study aimed to characterise the T. semipilosum reaction to three additional root-knot nematode species, viz. M. hapla, M. javanica, and M. incognita and if resistant, to determine if TRKR was the R source. Tests were conducted in peat-based potting mix in a temperature-controlled glasshouse using a subset of Mt-resistant and Mt-susceptible plants from the full-sib T. semipilosum population used to map TRKR. Mt resistant and susceptible white clover plants were challenged with Mt, M. hapla, M. incognita, and M. javanica for comparison. Experiments confirmed that T. semipilosum was able to host the four Meloidogyne species. Some T. semipilosum plants exhibited R to M. javanica and M. incognita whereas all were uniformly susceptible to M. hapla. There were no correlated reactions among the full-sib plants to challenge by the four nematode species, suggesting the genetic factor(s) conferring R to M. javanica and M. incognita are independent of the TRKR locus. Furthermore, the R to Mt is complete, with no galls formed on challenged plants whereas the observed R to M. javanica and M. incognita is apparently partial. White clover plants either resistant or susceptible to Mt were uniformly susceptible to M. hapla and M. javanica. These experiments suggest that T. semipilosum is a source of multiple nematode R loci. We plan to characterise further nematode resistances at loci in Trifolium genomes, and to investigate transfer of R alleles from T. semipilosum to white clover and other economic species.
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(326 KB)Adaptation to different grazing systems is an important attribute in white clover breeding. A set of 41 white clover breeding lines and nine commercial cultivars were evaluated under two grazing systems, sheep and cattle, in Manawatu. The objective was to identify lines with either specific or broad adaptation to these two different grazing systems. The trials were established in late autumn 1997 and completed in autumn 2000. Visual scores of clover yield for spring, summer, autumn and winter of year 2 and spring, summer and autumn of year 3 were analysed. There was significant (P<0.05) genotypic variation among lines and cultivars for yield across all seasons within each grazing system. Variance component analysis across all seasons and grazing treatments, indicated significant (P<0.05) genotypic variation among the lines and cultivars, and also significant (P<0.05) genotype-by-grazing system interaction. There was a lack of genetic correlation between the sheep and dairy grazing treatments. Breeding lines with specific adaptation to the sheep and dairy grazing systems were identified. Also, there were breeding lines with superior broad adaptation across the two grazing systems. All the breeding lines identified, were significantly (P<0.05) superior in performance to the best performing commercial controls in each grazing system, indicating successful achievement of genetic advance for specific and broad adaptation. These superior breeding lines were experimental synthetics developed using germplasm with New Zealand and European background
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(424 KB)White clover is an important forage legume in temperate areas of South America but the common cultivars used are winter-active, profuse flowering types and only persist for 2-3 years due to frequent moisture stress and hot summer conditions. A breeding programme was initiated to develop new types for intensive dairy and extensive cattle grazed pastures. Wide scale screening and crossing of germplasm from international and local sources revealed the potential of Ladino and ladino x local cultivar material for use in intensive pastures with good soils and grazing management. Improved persistence was a major objective for the extensive pastures and ecotype material collected from local farms together with crosses involving ladino and SE USA ecotypes were the best combinations. Experimental selections were developed for the two target environments and evaluated in ‘scope’ trials at three contrasting sites to determine herbage production and persistence potential. A ladino x local cultivar selection with large leaves, high herbage yields, extended winter to summer growth and ability to persist for at least 3 years was released as the cultivar ‘Goliath’ for intensive dairy-type pastures. A local ecotype selection with medium leaf size, slower establishment but high stolon density aiding persistence, and high seed yields was released as the cultivar ‘Aquiles’ for use in extensive pastures
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(314 KB)
Population changes were measured over 17 years within a highly variable bulk hybrid population of subterranean clover in a short and long growing season mediterranean-type environment in Western Australia. Flowering time was used as an indicator of evolutionary change and was highly responsive to environment. Markedly different populations evolved, with rapid selection for early flowering at the short growing season site and later flowering at the long growing season site. The use of bulk hybrid populations is suggested as a low-input means of breeding and selecting annual pasture legumes adapted to target environments and farming systems. While adapted genotypes can be selected after just 3 seasons, further adaptive fine-tuning occurs with increased homozygosity. The success of the method hinges on the original parents containing genes for desirable characters, trial sites being representative of target environments and trial management being representative of typical farm practice
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(382 KB)
Breeding tall fescue with rhizomes has the potential to improve turf persistence and recovery from wear. Most northern European and North American tall fescue cultivars can produce a few short rhizomes although they are considered to be non-rhizomatous. In contrast, almost all tall fescue plants from north-west Spain and northern Portugal have a high number of long rhizomes. Use of this rhizomatous germplasm in New Zealand turf grass breeding has been shown to provide valuable features, including winter activity, wear recovery and the ability to maintain a desirable winter green colour under our mild winter climate. The extent of rhizomatous spread within this germplasm responds readily to selection
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(314 KB)Modest and unreliable seed yield limits the usefulness of some forage tall fescue cultivars. In preliminary experiments, significant correlations for seed weight per panicle but not panicle number were established between spaced plants and sown rows of half-sib progeny derived from them. However, seed yield of the sown rows in the second year was not correlated with first year values. Half-sibling families of an elite breeding pool were sown in rows at three contrasting sites in autumn 1999. The following spring, panicle numbers were counted and in summer seed was harvested and weight per panicle calculated. Families varied significantly for seed yield and yield components, and family values were correlated between sites. Seedlings were raised from remnant seed of the best performing families (based on first year data at the 3 sites) and assessed pre-anthesis for panicle number. Selected plants were isolated and seed harvested. After progeny tests, three sub-sets of elite plants were isolated to produce improved selections. Plot trials sown at Lincoln (New Zealand) and at Pergamino (Argentina), showed significant seed yield improvements from the selections compared with “Grasslands Advance,” a standard cultivar derived from the same breeding pool
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(327 KB)Phalaris (Phalaris aquatica L.) is a perennial grass of Mediterranean origin used widely by the sheep and cattle industries of south-eastern Australia. Winter-active cultivars released since the 1970’s have the potential for higher herbage productivity than the earlier, semi-winter dormant cultivars but have been reported to be less persistent under sub-optimal grazing management and soil conditions. To improve genetic potential for persistence in winter-active phalaris, a program of recurrent selection was conducted by subjecting three populations of half-sib families to two cycles of selection for persistence under heavy, largely continuous grazing pressure. Cycle 2 progeny families and bulked seedlots of each generation were grown in separate grazed plot trials in Western Victoria and the Southern Tablelands and North-West Slopes of New South Wales from 1999-2003 to assess response to selection. Positive linear response to selection was observed in all populations at the Western Victorian and Southern Tablelands sites. Response to selection was absent and persistence was very low under higher temperature and drought stress on the North-West Slopes. This high level of genotype × environment interaction for persistence was also observed among final generation families. Families with better persistence than current winteractive cultivars at the two southern sites were identified in each population and a new cultivar is being formed from the parents.
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(407 KB)Hardinggrass has the potential to provide grazing during the fall to spring months in the south central USA. Here we describe a breeding program focused on developing improved hardinggrass cultivars for this region. More than 300 accessions were evaluated for persistence under heavy grazing in Oklahoma. The most promising of these accessions were evaluated for genetic diversity using AFLP markers. Accessions clustered closely in agreement with geographic origins with populations from Morocco representing a potentially novel source of germplasm. Two distinct breeding populations were constructed using this information. Additional populations, constructed using recurrent selection for survival under heavy grazing, have shown significantly greater persistence than currently available cultivars including ‘Grasslands Maru’. Research is underway to develop high throughput methods to profile alkaloid composition and concentration in hardinggrass. These methods will be applied to determine genotype and genotype x environment effects on alkaloid composition of elite breeding populations and commercial cultivars. Results of these evaluations, along with animal safety trials, will be critical in determining which populations to release as improved hardinggrass cultivars for the south central USA.
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