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Phillip Nichols - One of the best experts on this subject based on the ideXlab platform.
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novel disease host resistances in the world core collection of Trifolium subterraneum
Plant Disease, 2020Co-Authors: Ming Pei You, Phillip Nichols, Roseline Katusiime, Martin J. BarbettiAbstract:Glasshouse and field investigations of the phenotypic expressions of resistance of a 97-member World Core Collection of subterranean clover (Trifolium subterraneum) collected from its native Mediterranean habitat and representing approximately 80% of the total genetic diversity within the known 10,000 accessions of the species against the most important damping-off and root rot (Phytophthora clandestina, and Pythium irregulare) and foliar (Kabatiella caulivora, Uromyces trifolii-repentis, and Erysiphe trifoliorum) pathogens were performed. An additional 28 diverse cultivars were also included. Associations of these genotypes among 18 disease parameters and 17 morphological traits, and among these disease parameters and 24 climatic and eco-geographic variables from their collection sites, were examined. Many genotypes showed strong phenotypic expression of novel host disease resistance against one or more pathogens, enabling their potential deployment as disease-resistant parents in subterranean clover breeding programs. These new sources of resistance enable future "pyramiding" of different resistance genes to improve resistance against these pathogens. Of particular value were genotypes with multiple disease-resistance across soilborne and/or foliar diseases, because many of these pathogens co-occur. All diseases had some parameters significantly correlated with one or more morphological traits and with one or more sites of origin variables. In particular, there were significant negative correlations between damping-off (i.e., germination) and 8 of the 17 morphological characters. The outcomes of these studies provide crucial information to subterranean clover breeding programs, enabling them to simultaneously select genotypes with multiple resistance to co-occurring soilborne and foliar diseases and desirable traits to offer renewed hope for re-establishing a more productive subterranean clover livestock feedbase despite multiple diseases prevailing widely.
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morphological diversity within a core collection of subterranean clover Trifolium subterraneum l lessons in pasture adaptation from the wild
PLOS ONE, 2020Co-Authors: Abdi I Abdi, Phillip Nichols, Parwinder Kaur, Bradley J Wintle, William ErskineAbstract:Subterranean clover (Trifolium subterraneum L.) is a diploid self-pollinated annual pasture legume native to the Mediterranean region and widely sown in southern Australia and other countries with Mediterranean-type climates. This study utilised a core collection of 97 lines, representing around 80% of the genetic diversity of the species, to examine morphological diversity within subterranean clover. A total of 23 quantitative agro-morphological and 13 semi-quantitative morphological marker traits were assayed on the core collection and 28 diverse Australian cultivars as spaced plants in a replicated common garden experiment. Relationships between these traits and 24 climatic and edaphic parameters at their sites of origin were also examined within the core collection. Significant diversity was present for all traits. The Australian cultivars had similar levels of diversity to the core collection for several traits. Among the agro-morphological traits, time to flowering, leaf size and petiole diameter in mid-winter, plant area in late winter, maximum stem length, content of the oestogenic isoflavone biochanin A and total isoflavone content, were correlated with seven or more environmental variables. These can be considered highly adaptive, being the result of strong environmental selection pressure over time. For the first time in a clover species, morphological markers, including leaf mark, anthocyanin pigmentation and pubescence traits, have been associated with rainfall and soil parameters. This suggests they either have an adaptive role or the genes controlling them may be linked to other genes controlling adaptive traits. This study demonstrated the value of core collections to examine diversity within much larger global collections. It also identified adaptive traits from wild plants that can be utilised to develop more productive and persistent subterranean clover cultivars. The high heritability of these traits indicates that selection gains can be readily made.
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in vitro assisted single seed descent for breeding cycle compression in subterranean clover Trifolium subterraneum l
Crop & Pasture Science, 2017Co-Authors: Maria Pazosnavarro, Phillip Nichols, Marieclaire Castello, Richard G Bennett, Janine CroserAbstract:Subterranean clover (Trifolium subterraneum L.) is widely grown for its forage and ability to fix atmospheric nitrogen. Development of new varieties is constrained by the slow turnover time of generations, with only one generation per year possible under field conditions. We present an in vitro-assisted single-seed descent (IVASSD) technique, which enabled turnover of 2.7–6.1 generations per year across a diverse range of 27 T. subterraneum cultivars encompassing subspecies subterraneum, yanninicum and brachycalycinum. The IVASSD protocol accelerated the generation cycle in two ways: (i) time to floral initiation was minimised by growth under controlled temperature and extended photoperiod; and (ii) the seed-filling period was truncated and embryo and seed-coat dormancy avoided by the in vitro germination of immature seed on B5 medium plus L6KK overlay (0.525 mg gibberellic acid and 1.5 mg indole-butyric acid L–1). For the first time, an IVASSD system was validated on a full-scale breeding population with the production of 175 F7 recombinant inbred lines from an F4 population in less than one year. All F7 plants obtained were morphologically normal and fertile.
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in vitro reproduction in the annual pasture legumes subterranean clover Trifolium subterraneum l and french serradella ornithopus sativus brot
Grass and Forage Science, 2016Co-Authors: Marieclaire Castello, Phillip Nichols, Katia Stefanova, B J Nutt, Clinton Revell, Janine CroserAbstract:Pasture legumes are important components of both mixed farming rotations and permanent pastures in temperate climates. Breeding of two widely sown pasture legumes, subterranean clover (Trifolium subterraneum L.) and French serradella (Ornithopus sativus Brot.), is constrained by the long generation cycle, typically enabling only one generation per year. We hypothesized manipulation of culture medium and conditions would enable the development of a laboratory-based protocol for in vitro reproduction in subterranean clover and French serradella. In vitro flowering and viable seed set was induced from both species. For subterranean clover, the most effective treatment was culturing on modified MS medium with 1 μm kinetin and 0·1 m sucrose under a 100 μmol m−2 s−1 light intensity and continuous photoperiod. For French serradella, culture on a hormone-free B5 medium with 5 mm NH4Cl and 0·1 m sucrose under a 100 μmol m−2 s−1 light intensity and 20 h photoperiod was optimum. It is expected this technique will have application in accelerating generation turnover within breeding programs, for the study of factors influencing flowering in pasture legumes, and for the propagation of valuable yet enfeebled plants such as embryo-rescued hybrids.
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high variation in the percentage of root length colonised by arbuscular mycorrhizal fungi among 139 lines representing the species subterranean clover Trifolium subterraneum
Applied Soil Ecology, 2016Co-Authors: Megan H Ryan, Adam Stefanski, Phillip Nichols, Hans Lambers, Daniel R Kidd, R A Culvenor, G A Sandral, Zongjian Yang, Rebecca E HalingAbstract:Abstract Development of more phosphorus (P)-efficient pasture legumes could improve the P balance of pasture systems. Trifolium subterraneum (subterranean clover) is the most widely-grown annual pasture legume in southern Australia and is host to arbuscular mycorrhizal fungi (AMF). To examine the potential to alter colonisation level through breeding, 97 lines from the core collection of subterranean clover (core lines) and 42 cultivars (cultivar lines) were grown in a glasshouse in a low-P sandy acid field soil with indigenous AMF (Experiment 1). To examine the robustness of rankings, two cultivars (Riverina and Woogenellup) were also grown in 11 field soils (Experiment 2). To examine whether the presence of AMF changed other root traits important for P uptake, cultivars Riverina and Woogenellup were grown in two low-P field soils (sand, sandy loam), either pasteurised to remove indigenous AMF or unpasteurised, and with and without addition of inoculum of AMF (Experiment 3). The range of colonisation for core lines and cultivar lines was similar (∼12–68% of root length), however, the core lines had higher mean colonisation (37% vs 33%) and a greater proportion of lines with >40% of root length colonised (41% vs 24% of lines). Woogenellup was more heavily colonised than Riverina in eight soils and had a similar level of colonisation in three soils. In the sand, pasteurisation resulted in shoot DM increasing by up to 100% (possibly due to reduction in root diseases). Inoculation, in pasteurised and unpasteurised soil, resulted in an increase in shoot DM, shoot P concentration and shoot P content of ∼100%, increased average root diameter by up to 13%, decreased specific root length by up 30% and decreased root mass ratio; effects on average root hair length were variable. In the unpasteurised sandy loam, shoot P concentrations were higher than in the sand, and inoculation slightly increased shoot P concentration, but not shoot DM; the effects of inoculation on root traits were mostly small. We conclude that potential may exist to select subterranean clover for higher or lower colonisation by AMF using cultivar lines. Also, indigenous AMF may be less effective at enhancing plant P uptake and growth than inoculants. Finally, key root traits for enhancing plant P-uptake may change in the presence of AMF, but not sufficiently so to warrant deliberate inclusion or exclusion of AMF when screening germplasm for such traits.
Martin J. Barbetti - One of the best experts on this subject based on the ideXlab platform.
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novel disease host resistances in the world core collection of Trifolium subterraneum
Plant Disease, 2020Co-Authors: Ming Pei You, Phillip Nichols, Roseline Katusiime, Martin J. BarbettiAbstract:Glasshouse and field investigations of the phenotypic expressions of resistance of a 97-member World Core Collection of subterranean clover (Trifolium subterraneum) collected from its native Mediterranean habitat and representing approximately 80% of the total genetic diversity within the known 10,000 accessions of the species against the most important damping-off and root rot (Phytophthora clandestina, and Pythium irregulare) and foliar (Kabatiella caulivora, Uromyces trifolii-repentis, and Erysiphe trifoliorum) pathogens were performed. An additional 28 diverse cultivars were also included. Associations of these genotypes among 18 disease parameters and 17 morphological traits, and among these disease parameters and 24 climatic and eco-geographic variables from their collection sites, were examined. Many genotypes showed strong phenotypic expression of novel host disease resistance against one or more pathogens, enabling their potential deployment as disease-resistant parents in subterranean clover breeding programs. These new sources of resistance enable future "pyramiding" of different resistance genes to improve resistance against these pathogens. Of particular value were genotypes with multiple disease-resistance across soilborne and/or foliar diseases, because many of these pathogens co-occur. All diseases had some parameters significantly correlated with one or more morphological traits and with one or more sites of origin variables. In particular, there were significant negative correlations between damping-off (i.e., germination) and 8 of the 17 morphological characters. The outcomes of these studies provide crucial information to subterranean clover breeding programs, enabling them to simultaneously select genotypes with multiple resistance to co-occurring soilborne and foliar diseases and desirable traits to offer renewed hope for re-establishing a more productive subterranean clover livestock feedbase despite multiple diseases prevailing widely.
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Genetic improvement of subterranean clover (Trifolium subterraneum L.). 2. Breeding for disease and pest resistance
Crop and Pasture Science, 2014Co-Authors: Phillip Nichols, Roger A. C. Jones, T.j. Ridsdill-smith, Martin J. BarbettiAbstract:Subterranean clover (Trifolium subterraneum L.) is the most widely sown pasture legume in southern Australia and resistance to important diseases and pests has been a major plant-breeding objective. Kabatiella caulivora, the cause of clover scorch, is the most important foliar fungal pathogen, and several cultivars have been developed with resistance to both known races. Screening of advanced breeding lines has been conducted to prevent release of cultivars with high susceptibility to other important fungal foliar disease pathogens, including rust (Uromyces trifolii-repentis), powdery mildew (Oidium sp.), cercospora (Cercospora zebrina) and common leaf spot (Pseudopeziza trifolii). Several oomycete and fungal species cause root rots of subterranean clover, including Phytophthora clandestina, Pythium irregulare, Aphanomyces trifolii, Fusarium avenaceum and Rhizoctonia solani. Most breeding efforts have been devoted to resistance to P. clandestina, but the existence of different races has confounded selection. The most economically important virus diseases in subterranean clover pastures are Subterranean clover mottle virus and Bean yellow mosaic virus, while Subterranean clover stunt virus, Subterranean clover red leaf virus (local synonym for Soybean dwarf virus), Cucumber mosaic virus, Alfalfa mosaic virus, Clover yellow vein virus, Beet western yellows virus and Bean leaf roll virus also cause losses. Genotypic differences for resistance have been found to several of these fungal, oomycete and viral pathogens, highlighting the potential to develop cultivars with improved resistance. The most important pests of subterranean clover are redlegged earth mite (RLEM) (Halotydeus destructor), blue oat mite (Penthaleus major), blue-green aphid (Acyrthosiphon kondoi) and lucerne flea (Sminthurus viridis). New cultivars have been bred with increased RLEM cotyledon resistance, but limited selection has been conducted for resistance to other pests. Screening for disease and pest resistance has largely ceased, but recent molecular biology advances in subterranean clover provide a new platform for development of future cultivars with multiple resistances to important diseases and pests. However, this can only be realised if skills in pasture plant pathology, entomology, pre-breeding and plant breeding are maintained and adequately resourced. In particular, supporting phenotypic disease and pest resistance studies and understanding their significance is critical to enable molecular technology investments achieve practical outcomes and deliver subterranean clover cultivars with sufficient pathogen and pest resistance to ensure productive pastures across southern Australia.
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amelioration of root disease of subterranean clover Trifolium subterraneum by mineral nutrients
Crop & Pasture Science, 2012Co-Authors: Tiernan A Orourke, Krishnapillai Sivasithamparam, Megan H Ryan, Tim Scanlon, Martin J. BarbettiAbstract:Subterranean clover (Trifolium subterraneum) is a key pasture legume across southern Australia and elsewhere. Decline in subterranean clover pastures was first recognised in Australia during the 1960s and manifests as an increase in weeds and a decrease in desirable legume species. While both root disease and poor nutrition contribute to subterranean clover pasture decline, the relationships between root disease and nutrition have not been determined. The objective of this study was to define these relationships. Field experiments were undertaken to determine the nutritional and pathogen status of soils and subterranean clover from three Western Australian field sites. Subsequently, controlled environment experiments were undertaken to determine the relative severities of tap and lateral root disease and growth of plants when soil cores taken from these three field sites were amended with a complete nutrient solution or a range of individual macro- or micronutrient treatments. Application of a ‘Hoaglands’ complete nutrient solution decreased the severity of tap root disease by an average of 45% and lateral root disease by 32%. Amendment with K alone reduced the severity of tap root disease an average of 32%; while the application of N alone reduced the severity of tap root disease by 33% and lateral root disease by 27%. Application of Hoaglands, K, N or Zn increased shoot and root dry weight, while Mo only increased shoot dry weight. This is the first report to show that mineral nutrients can substantially ameliorate root disease in subterranean clover. The results demonstrate that while root disease limits plant growth, improvement in the nutritional status of nutrient-impoverished soils can significantly reduce root disease. There is significant potential to incorporate nutrient amendments into an integrated and more sustainable approach to better manage root disease and to increase productivity of pasture legumes where soils are inherently nutrient deficient in one or more nutrients.
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taxonomic and pathogenic characteristics of a new species aphanomyces trifolii causing root rot of subterranean clover Trifolium subterraneum in western australia
Crop & Pasture Science, 2010Co-Authors: Tiernan A Orourke, Martin J. Barbetti, Megan H Ryan, Krishnapillai Sivasithamparam, Jamshid FatehiAbstract:Subterranean clover (Trifolium subterraneum) is grown extensively as a pasture legume in agronomic regions with Mediterranean-type climates in parts of Africa, Asia, Australia, Europe, North America and South America. Root diseases of subterranean clover, especially those caused by oomycete pathogens including Aphanomyces, Phytophthora and Pythium, greatly reduce productivity by significantly decreasing germination, seedling establishment, plant survival and seed set. For this reason, experiments were conducted to determine the species of Aphanomyces causing root disease on subterranean clover in the high-rainfall areas of south-west Western Australia. The effects of flooding, temperature and inoculum concentration on the development of root disease on subterranean clover caused by this Aphanomyces sp. were also investigated as was its host range. Morphological and molecular characteristics were used to identify the pathogen as a new species Aphanomyces trifolii sp. nov. (O’Rourke et al.), which forms a distinct clade with its nearest relative being A. cladogamus. A. trifolii caused significant lateral root pruning as well as hypocotyl collapse and tap root disease of subterranean clover. The level of disease was greater in treatments where soil was flooded for 24 h rather than for 6 h or in unflooded treatments. The pathogen caused more disease at 18/13oC than at lower (10/5oC) or higher (25/20oC) temperatures. The pathogen caused more disease at 1% inoculum than at 0.5 or 0.2% (% inoculum : dry weight of soil). In greenhouse trials, A. trifolii also caused root disease on annual medic (M. polymorpha and M. truncatula), dwarf beans (Phaseolus vulgaris) and tomatoes (Solanum lycopersicum). However, the pathogen did not cause disease on peas (Pisum sativum), chickpea (Cicer arietinum), wheat (Triticum aestivum), annual ryegrass (Lolium rigidium) or capsicum (Capsicum annuum). A. trifolii is a serious pathogen in the high-rainfall areas of south-west Western Australia and is likely a significant cause of root disease and subsequent decline in subterranean clover pastures across southern Australia.
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infection processes and involvement of defense related genes in the expression of resistance in cultivars of subterranean clover Trifolium subterraneum to phytophthora clandestina
Phytopathology, 2010Co-Authors: Krishnapillai Sivasithamparam, Martin J. BarbettiAbstract:ABSTRACT Studies on infection processes and gene expression were done to determine differential responses of cultivars of Trifolium subterraneum resistant and susceptible to infection by races of Phytophthora clandestina. In the infection process study, one race was inoculated onto the roots of T. subterraneum cvs. Woogenellup and Junee (compatible or incompatible interactions, respectively). There were no differences in relation to the processes of cyst attachment, germination, and hyphal penetration. There were, however, major differences in infection progression observed post-penetration between compatible and incompatible interactions. In susceptible cv. Woogenellup, hyphae grew into the vascular bundles and produced intercellular antheridia and oogonia in the cortex and stele by 4 days postinoculation (dpi), oospores in the cortex and stele by 8 dpi, when sporangia were evident on the surface of the root. Infected taproots were discolored. Early destruction of taproots prevented emergence of lateral ...
Parwinder Kaur - One of the best experts on this subject based on the ideXlab platform.
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an improved protocol for agrobacterium mediated transformation in subterranean clover Trifolium subterraneum l
International Journal of Molecular Sciences, 2021Co-Authors: Fernando Perez Rojo, William Erskine, Sumedha Seth, Parwinder KaurAbstract:Subterranean clover (Trifolium subterraneum) is the most widely grown annual pasture legume in southern Australia. With the advent of advanced sequencing and genome editing technologies, a simple and efficient gene transfer protocol mediated by Agrobacterium tumefaciens was developed to overcome the hurdle of genetic manipulation in subterranean clover. In vitro tissue culture and Agrobacterium transformation play a central role in testing the link between specific genes and agronomic traits. In this paper, we investigate a variety of factors affecting the transformation in subterranean clover to increase the transformation efficiency. In vitro culture was optimised by including cefotaxime during seed sterilisation and testing the best antibiotic concentration to select recombinant explants. The concentrations for the combination of antibiotics obtained were as follows: 40 mg L-1 hygromycin, 100 mg L-1 kanamycin and 200 mg L-1 cefotaxime. Additionally, 200 mg L-1 cefotaxime increased shoot regeneration by two-fold. Different plant hormone combinations were tested to analyse the best rooting media. Roots were obtained in a medium supplemented with 1.2 µM IAA. Plasmid pH35 containing a hygromycin-resistant gene and GUS gene was inoculated into the explants with Agrobacterium tumefaciens strain AGL0 for transformation. Overall, the transformation efficiency was improved from the 1% previously reported to 5.2%, tested at explant level with Cefotaxime showing a positive effect on shooting regeneration. Other variables in addition to antibiotic and hormone combinations such as bacterial OD, time of infection and incubation temperature may be further tested to enhance the transformation even more. This improved transformation study presents an opportunity to increase the feeding value, persistence, and nutritive value of the key Australian pasture.
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morphological diversity within a core collection of subterranean clover Trifolium subterraneum l lessons in pasture adaptation from the wild
PLOS ONE, 2020Co-Authors: Abdi I Abdi, Phillip Nichols, Parwinder Kaur, Bradley J Wintle, William ErskineAbstract:Subterranean clover (Trifolium subterraneum L.) is a diploid self-pollinated annual pasture legume native to the Mediterranean region and widely sown in southern Australia and other countries with Mediterranean-type climates. This study utilised a core collection of 97 lines, representing around 80% of the genetic diversity of the species, to examine morphological diversity within subterranean clover. A total of 23 quantitative agro-morphological and 13 semi-quantitative morphological marker traits were assayed on the core collection and 28 diverse Australian cultivars as spaced plants in a replicated common garden experiment. Relationships between these traits and 24 climatic and edaphic parameters at their sites of origin were also examined within the core collection. Significant diversity was present for all traits. The Australian cultivars had similar levels of diversity to the core collection for several traits. Among the agro-morphological traits, time to flowering, leaf size and petiole diameter in mid-winter, plant area in late winter, maximum stem length, content of the oestogenic isoflavone biochanin A and total isoflavone content, were correlated with seven or more environmental variables. These can be considered highly adaptive, being the result of strong environmental selection pressure over time. For the first time in a clover species, morphological markers, including leaf mark, anthocyanin pigmentation and pubescence traits, have been associated with rainfall and soil parameters. This suggests they either have an adaptive role or the genes controlling them may be linked to other genes controlling adaptive traits. This study demonstrated the value of core collections to examine diversity within much larger global collections. It also identified adaptive traits from wild plants that can be utilised to develop more productive and persistent subterranean clover cultivars. The high heritability of these traits indicates that selection gains can be readily made.
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genetic diversity linked to haplotype variation in the world core collection of Trifolium subterraneum for boron toxicity tolerance provides valuable markers for pasture breeding
Frontiers in Plant Science, 2019Co-Authors: Hediyeh Tahghighi, William Erskine, Maria Pazosnavarro, Richard G Bennett, Philipp E Bayer, Parwinder KaurAbstract:In alkaline soils in arid and semi-arid areas toxic concentrations of the micronutrient boron (B) are problematic for many cereal and legume crops. Molecular markers have been developed for B toxicity in cereals and Medicago. There is a need for such tools in clovers – Trifolium. To this end we undertook a genome-wide association study (GWAS) with a diversity panel of subterranean clover (Trifolium subterraneum L.), an established model pasture legume for genetic and genomic analyses for the genus. The panel comprised 124 T. subterraneum genotypes (97 core collection accessions and 27 Australian cultivars). Substantial and useful diversity in B toxicity tolerance was found in T. subterraneum. Such variation was continuously distributed and exhibited a high broadsense heritability H2 = 0.92. Among the subspecies of T. subterraneum, ssp. brachycalycinum was most susceptible to B toxicity (P<0.05). From the GWAS the most important discoveries were Single Nucleotide Polymorphisms (SNPs) located on Chr 1, 2 and 3 which mapped to haplotype blocks providing potential genes for a B toxicity tolerance assay and meriting further inverstigation. A SNP identified on Chr 1 aligned with Medicago truncatula respiratory burst oxidase-like protein (TSub_ g2235). This protein is known to respond to abiotic and biotic stimuli. The identification of these novel potential genes and their use to design markers for marker-assisted selection offer a pathway in pasture legumes to manage B toxicity by exploiting B tolerance.
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genetic improvement of subterranean clover Trifolium subterraneum l 1 germplasm traits and future prospects
Crop & Pasture Science, 2013Co-Authors: Phillip Nichols, Kioumars Ghamkhar, Kevin Foster, Parwinder Kaur, E Piano, Luciano Pecetti, W J CollinsAbstract:Subterranean clover (Trifolium subterraneum L.) is the most widely sown annual pasture legume species in southern Australia, valued in the livestock and grains industries as a source of high-quality forage and for its ability to fix atmospheric nitrogen. From its initial accidental introduction into Australia in the 19th Century and subsequent commercialisation in the early 1900s, 45 cultivars have been registered in Australia. These consist of 32 cultivars of ssp. subterraneum, eight of ssp. yanninicum, and five of ssp. brachycalycinum and range in flowering time from 77 to 163 days from sowing, enabling the species to be grown in a diversity of rainfall environments, soil types, and farming systems. Eleven of these cultivars are introductions from the Mediterranean region, 15 are naturalised strains collected in Australia,18aretheproductsofcrossbreeding,andoneisderivedfrommutagenesis.CultivarsdevelopedinItalyhavebeen commercialised for the local market, whereas other cultivars developed in Spain, Portugal, and France have not had commercial seed production. Important traits exploited include: (i) selection for low levels of the oestrogenic isoflavone formononetin, which causes reduced ewe fertility; (ii) increased levels of dormancy imposed by seed-coat impermeability (hard seeds) for cultivars aimed at crop rotations or unreliable rainfall environments; (iii) strong burr-burial ability to maximise seed production; (iv) resistance to important disease pathogens for cultivars aimed at medium- and high-rainfall environments,particularlytoKabatiellacaulivoraandrootrotpathogens;(v)resistancetopests,particularlyredleggedearth mites;and(vi)selectionforuniqueleafmarkingsandothermorphologicaltraits(wherepossible)toaidcultivaridentification. Cultivardevelopmenthasbeenaidedbyalargegeneticresourceof~10000accessions,assembledfromitscentreoforiginin theMediterranean Basin,WestAsia, andtheAtlanticcoast ofWestern Europe,inaddition tonaturalisedstrains collected in Australia. The development of a core collection of 97 accessions, representing almost 80% of the genetic diversity of the species,andageneticmap,providesaplatformfordevelopmentoffuturecultivarswithnewtraitstobenefitthelivestockand grains industries. New traits being examined include increased phosphorous-use efficiency and reduced methane emissions fromgrazingruminantlivestock.Economicanalysesindicatethatfuturetraitdevelopmentshouldfocusontraitscontributing to increased persistence and autumn-winter productivity, while other potential traits include increased nutritive value (particularlyofsenescedmaterial),increasedN2 fixationability,andtolerancetocheapherbicides.Beneficialcompoundsfor animal and human health may also be present within the species for exploitation.
Megan H Ryan - One of the best experts on this subject based on the ideXlab platform.
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differences in nutrient foraging among Trifolium subterraneum cultivars deliver improved p acquisition efficiency
Plant and Soil, 2018Co-Authors: Rebecca E Haling, Adam Stefanski, Hans Lambers, Daniel R Kidd, Megan H Ryan, Lawrie K Brown, G A Sandral, Timothy S George, Richard J SimpsonAbstract:The growth and root morphology responses to soil phosphorus (P) fertility by five cultivars of Trifolium subterraneum (a temperate annual pasture legume) were examined to assess whether differences in root morphology and/or root acclimation to P stress influenced P-acquisition by the clover varieties, or their critical P requirements (i.e. the rate of P supply needed for maximum shoot yield). The clovers were grown as microswards in soil with P stratified in a topsoil layer to mimic growth conditions and soil P availability in a pasture. Yield and P content of shoots, and roots from the topsoil and subsoil layers was determined after 5 weeks growth in a controlled-environment cabinet. The lengths, diameters, and root hair lengths of nutrient foraging roots from the topsoil layer were quantified. The shoot yield of the cultivars was similar when grown with high soil P fertility. However, the cultivars varied up to 1.5-fold in their ability to yield at low levels of soil P supply, and by 1.6-fold in their critical P requirements. All cultivars acclimated to low P soil by increasing root length density in the topsoil but those that yielded relatively well did so by maintaining a large root hair cylinder volume (i.e. they explored more soil) under low soil P conditions. This was associated with maintenance of dry matter allocations to topsoil roots and higher specific root lengths. Both factors assisted development of high root length density for nutrient foraging. Root acclimation responses to P were compared among the cultivars at equivalent relative shoot yields to assess the influence of plant P stress as a trigger for nutrient foraging. The least P-efficient cultivars slowed their allocation of dry matter to foraging roots at lower levels of P stress. The results suggest variation within T. subterraneum for root proliferation and specific root length could be targeted in breeding for improved P-acquisition efficiency.
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root morphology acclimation to phosphorus supply by six cultivars of Trifolium subterraneum l
Plant and Soil, 2017Co-Authors: Robert P Jeffery, Richard J Simpson, Hans Lambers, Daniel R Kidd, Megan H RyanAbstract:Trifolium subterraneum L. is the predominant annual pasture legume in southern Australia. Cultivars with improved phosphorus (P) foraging ability would improve the P-use efficiency of agricultural systems. We therefore investigated variation in root traits related to P-uptake among six cultivars. Micro-swards were grown at six levels of P in field soil with indigenous arbuscular mycorrhizal (AM) fungi for six weeks. Dry matter yield, tissue P concentration, rhizosphere carboxylates, AM fungal colonisation and root morphological traits were measured. The cultivars showed similar shoot and root yield responses to P supply. Average root diameter did not change, specific root length (SRL) increased and root tissue density (RTD) decreased with increased P supply. Amounts of total rhizosphere carboxylates were low (<1.2 nmol cm−1 root). The percentage of root length colonised by AM fungi was greatest (29–43 %) at an intermediate level (8 mg kg−1 dry soil) of P supply. Most differences among cultivars were reasonably consistent across P supply levels, indicating greater numbers of lines could be screened reliably at a single P level. Low colonisation by AM fungi at low P supply deserves consideration when selecting soils for cultivar comparisons. Increased SRL and decreased RTD at high P supply likely result from self-shading within the micro-swards and warrant further investigation.
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high variation in the percentage of root length colonised by arbuscular mycorrhizal fungi among 139 lines representing the species subterranean clover Trifolium subterraneum
Applied Soil Ecology, 2016Co-Authors: Megan H Ryan, Adam Stefanski, Phillip Nichols, Hans Lambers, Daniel R Kidd, R A Culvenor, G A Sandral, Zongjian Yang, Rebecca E HalingAbstract:Abstract Development of more phosphorus (P)-efficient pasture legumes could improve the P balance of pasture systems. Trifolium subterraneum (subterranean clover) is the most widely-grown annual pasture legume in southern Australia and is host to arbuscular mycorrhizal fungi (AMF). To examine the potential to alter colonisation level through breeding, 97 lines from the core collection of subterranean clover (core lines) and 42 cultivars (cultivar lines) were grown in a glasshouse in a low-P sandy acid field soil with indigenous AMF (Experiment 1). To examine the robustness of rankings, two cultivars (Riverina and Woogenellup) were also grown in 11 field soils (Experiment 2). To examine whether the presence of AMF changed other root traits important for P uptake, cultivars Riverina and Woogenellup were grown in two low-P field soils (sand, sandy loam), either pasteurised to remove indigenous AMF or unpasteurised, and with and without addition of inoculum of AMF (Experiment 3). The range of colonisation for core lines and cultivar lines was similar (∼12–68% of root length), however, the core lines had higher mean colonisation (37% vs 33%) and a greater proportion of lines with >40% of root length colonised (41% vs 24% of lines). Woogenellup was more heavily colonised than Riverina in eight soils and had a similar level of colonisation in three soils. In the sand, pasteurisation resulted in shoot DM increasing by up to 100% (possibly due to reduction in root diseases). Inoculation, in pasteurised and unpasteurised soil, resulted in an increase in shoot DM, shoot P concentration and shoot P content of ∼100%, increased average root diameter by up to 13%, decreased specific root length by up 30% and decreased root mass ratio; effects on average root hair length were variable. In the unpasteurised sandy loam, shoot P concentrations were higher than in the sand, and inoculation slightly increased shoot P concentration, but not shoot DM; the effects of inoculation on root traits were mostly small. We conclude that potential may exist to select subterranean clover for higher or lower colonisation by AMF using cultivar lines. Also, indigenous AMF may be less effective at enhancing plant P uptake and growth than inoculants. Finally, key root traits for enhancing plant P-uptake may change in the presence of AMF, but not sufficiently so to warrant deliberate inclusion or exclusion of AMF when screening germplasm for such traits.
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hotspots and gaps in the world collection of subterranean clover Trifolium subterraneum l
The Journal of Agricultural Science, 2015Co-Authors: Kioumars Ghamkhar, Phillip Nichols, William Erskine, R Snowball, M Murillo, R Appels, Megan H RyanAbstract:Subterranean clover (Trifolium subterraneum L.) is the most important annual pasture legume in the winter-dominant rainfall areas of Southern Australia. Systematic germplasm collections of subterranean clover from its centre of origin have been made since the 1950s, particularly by Australian scientists, in order to broaden the genetic base of the species. The present study reports on a meta-analysis of the distribution of the world collection of subterranean clovers and their relationships to eco-geographic variables of the collection sites in their native habitat. Diversity hotspots (areas rich in number of accessions and containing a high diversity of sub-species) and also gaps (areas with particular traits un- or under-represented in collections) were identified. This was achieved using a stratified data system to evaluate eco-geographical and agro-morphological data which incorporated three tiers of information for the subterranean clover collection: (1) information from each collection site, including ecological data; (2) information on the phenotypic diversity within each collection site; and (3) plant agro-morphological data from each sample grown under controlled conditions. Correlations were found between some eco-geographic conditions and agronomic performance. These included correlations between latitude and flowering time, mean temperature in winter and winter productivity and precipitation in summer and seed dormancy. The present study concluded that subterranean clover versatility is greater than suggested in the past. The results of the current analysis provide a guide for future collecting missions to specific regions towards areas of maximum diversity (hotspots) and unknown diversity (gaps).
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do arbuscular mycorrhizas or heterotrophic soil microbes contribute toward plant acquisition of a pulse of mineral phosphate
Plant and Soil, 2013Co-Authors: Nazanin K Nazeri, Hans Lambers, Mark Tibbett, Megan H RyanAbstract:Aims We investigated the role of arbuscular mycorrhizal fungi (AMF) and heterotrophic soil microbes in the uptake of phosphorus (P) by Trifolium subterraneum from a pulse.
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foliar zinc biofortification effects in lolium rigidum and Trifolium subterraneum grown in cadmium contaminated soil
PLOS ONE, 2017Co-Authors: M J Poblaciones, Paul Damon, Zed RengelAbstract:Zinc (Zn) is an important micronutrient that can alleviate cadmium (Cd) toxicity to plants and limit Cd entry into the food chain. However, little is known about the Zn-Cd interactions in pasture plants. We characterized the effects of foliar Zn application and Cd uptake by ryegrass (Lolium rigidum L.) and clover (Trifolium subterraneum L.) grown on Cd-contaminated soils; all combinations of foliar Zn applications (0, 0.25 and 0.5% (w/v) ZnSO4·7H2O) and soil Cd concentrations (0, 2.5 and 5 mg Cd kg-1) were tested. For both plant species, soil concentrations of DTPA-extractable Cd and Zn increased with an increase in the Cd and Zn treatments, respectively. Compared with L. rigidum, T. subterraneum accumulated, respectively, 3.3- and 4.1-fold more Cd in the 2.5-Cd and 5-Cd treatments and about 1.3-, 2.3- and 2.8-fold more Zn in the No-Zn, 0.25-Zn and 0.5-Zn treatments. Also, DTPA-Zn concentration was higher in soil after T. subterraneum than L. rigidum growth regardless of Zn applications. Foliar application of 0.25% (w/v) Zn significantly decreased the total Cd concentration in shoots of both species grown in the Cd-contaminated soil and ameliorated the adverse effects of Cd exposure on root growth, particularly in T. subterraneum.
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biomass yield nutritive value and accumulation of minerals in Trifolium subterraneum l as affected by fungal endophytes
Plant and Soil, 2016Co-Authors: Santiago Lledo, Sara Rodrigo, M J Poblaciones, O SantamariaAbstract:Trifolium subterraneum is a legume species which is valuable for feeding livestock and frequently used as a forage crop in countries with temperate or Mediterranean-like climates. The aim of the present work was to evaluate the effect of six leaf fungal endophytes on biomass production, nutritive value and mineral status of T. subterraneum forage. Plants were inoculated with each of seven treatments (six endophytes + control) at two different growth stages. After inoculation, two experiments (under greenhouse and field conditions) were established. Endophytes affected biomass yield, nutritive value and mineral status of T. subterraneum forage, but effects varied between experiments and depended on fungal species. E202 (Chaetosphaeronema sp.) increased forage productivity by around 80 % in the field. Fusarium lateritium and E244 (Pleosporales) reduced Al concentration, and Epicoccum nigrum reduced Pb of the forage in the greenhouse experiment. An increase in essential nutrients, such as Zn, was mainly produced by Stemphylium globuliferum. This study demonstrated that inoculation with endophytes can increase forage productivity and help reduce potential nutrient deficiencies and/or potential mineral toxicity in T. subterraneum.
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endophytic mycobiota associated with Trifolium subterraneum growing under semiarid conditions
Annals of Applied Biology, 2016Co-Authors: Santiago Lledo, O Santamaria, Sara Rodrigo, M J PoblacionesAbstract:Endophytic fungi were isolated from leaves and stems of Trifolium subterraneum at 10 sites in Extremadura (southwestern Spain), with the aims of (a) determining the fungal composition and its genetic variability and (b) analysing the effect of sampling site and tissue type on fungal diversity, frequency and species distribution. A total of 773 endophytic isolates were obtained from 100 plant specimens. Based on their morphological characteristics and internal transcribed spacer region (ITS) sequencing, a total of 54 species were identified. Most taxa were included in phylum Ascomycota, prevailing classes Dothideomycetes and Sordariomycetes. Almost 70% of the species showed a clear preference for one of the tissue types, showing clear organ specificity, and many of them had a very local distribution. For environmental variables, Mg in soil and precipitation had a significant influence on fungal diversity and species distribution. The leaf/stem fungal endophytes of T. subterraneum have been characterised for the first time. The results provide a reliable framework for further research on the functional roles of endophytes and eventual applications focused on this pasture species.
