Search

Drought may impact plant–soil biotic interactions in ways that modify aboveground herbivore performance, but the outcomes of such biotic interactions under future climate are not yet clear. We performed a growth chamber experiment to assess how long‐term, drought‐driven changes in belowground communities influence plant growth and herbivore performance using a plant–soil feedback experimental framework. We focussed on two common pasture legumes—lucerne, Medicago sativa L., and white clover, Trifolium repens L. (both Fabaceae)—and foliar herbivores—cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), and two‐spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). Soil was collected from a field facility where rainfall had been manipulated for 6 years, focussing on treatments representing ambient rainfall and prolonged drought (50% reduction relative to ambient), to consider the effects of biological legacies mediated by the prolonged drought. All soils were sterilized and re‐inoculated to establish the respective home (i.e. where a given plant is cultivated in its own soil) and away (i.e. where a given plant is cultivated in another species' soil) treatments in addition to a sterile control. We found that the relative growth rate (RGR) and relative consumption of larvae were significantly lower on lucerne grown in soil with ambient rainfall legacies conditioned by white clover. Conversely, the RGR of insect larvae was lower on white clover grown in soil with prolonged drought legacies conditioned by lucerne. Two‐spotted spider mite populations and area damage (mm2) were significantly reduced on white clover grown in lucerne‐conditioned soil in drought legacies. The higher number of nodules found on white clover in lucerne‐conditioned soil suggests that root–rhizobia associations may have reduced foliar herbivore performance. Our study provides evidence that foliar herbivores are affected by plant–soil biotic interactions and that prolonged drought may influence aboveground–belowground linkages with potential broader ecosystem impacts. [ABSTRACT FROM AUTHOR]

Trifolium repens is a well-known herbaceous, perennial herb and has been extensively used in the traditional medicine system over the years. Various parts of the plant are traditionally used as a curative agent against several health ailments such as skin problems, wound healing, stomach disorders, sedative, fever, antiseptic, analgesic, expectorant, psoriasis and eczema. To maximise the plant's potential for usage in the future, the review also aims to update information about its significant pharmacological properties. The ethnomedicinal benefits of T. repens have been well studied; however, the facets of the plant have not been explored yet. The current review outlines several bioactive compounds quantified from T. repens and a few of them namely quercetin, kaempferol, myricetin, acacetin and linamarin, have been reported to have biological activities such as antibacterial, antifungal, antileishmanial, anti-inflammatory, antiaging and anti-hepatotoxic activities. A significant number of in vitro studies have been done on the plant extract, but little is known about the isolation and efficacy of the potent natural bioactive compounds of T. repens. The bioactive compounds in T. repens can be used for advanced drug development against various health disorders. [ABSTRACT FROM AUTHOR]

Copyright of Acta Prataculturae Sinica is the property of Acta Prataculturae Sinica Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

White clover (Trifolium repens L.) is an important forage and aesthetic plant species, but it is susceptible to drought and heat stress. The phytohormone auxin regulates several aspects of plant development and alleviates the effects of drought stress in plants, including white clover, by involving auxin/indole acetic acid (Aux/IAA) family genes. However, Aux/IAA genes and the underlying mechanism of auxin-mediated drought response remain elusive in white clover. To extend our understanding of the multiple functions of Aux/IAAs, the current study described the characterization of a member of the Aux/IAA family TrIAA27 of white clover. TrIAA27 protein had conserved the Aux/IAA family domain and shared high sequence similarity with the IAA27 gene of a closely related species and Arabidopsis. Expression of TrIAA27 was upregulated in response to heavy metal, drought, salt, NO, Ca2+, H2O2, Spm, ABA, and IAA treatments, while downregulated under cold stress in the roots and leaves of white clover. TrIAA27 protein was localized in the nucleus. Constitutive overexpression of TrIAA27 in Arabidopsis thaliana led to enhanced hypocotyl length, root length, plant height, leaf length and width, and fresh and dry weights under optimal and stress conditions. There was Improved photosynthesis activity, chlorophyll content, survival rate, relative water content, endogenous catalase (CAT), and peroxidase (POD) concentration with a significantly lower electrolyte leakage percentage, malondialdehyde (MDA) content, and hydrogen peroxide (H2O2) concentration in overexpression lines compared to wild-type Arabidopsis under drought and salt stress conditions. Exposure to stress conditions resulted in relatively weaker roots and above-ground plant growth inhibition, enhanced endogenous levels of major antioxidant enzymes, which correlated well with lower lipid peroxidation, lower levels of reactive oxygen species, and reduced cell death in overexpression lines. The data of the current study demonstrated that TrIAA27 is involved in positively regulating plant growth and development and could be considered a potential target gene for further use, including the breeding of white clover for higher biomass with improved root architecture and tolerance to abiotic stress. [ABSTRACT FROM AUTHOR]

The Fabaceae genus Trifolium comprises around 250 species widely distributed worldwide, with the temperate Northern Hemisphere exhibiting the highest variety. The plants in this genus are widely used as livestock fodder crops and are particularly significant economically. This study's objective included isolating bacteria from the root nodules of the Trifolium repens plant and diagnosing it at the molecular and microbiological levels. T. repens root nodules were used as the source of an endophytic bacteria isolated on Yeast Extract Mannitol (YEM) media that had solidified and diagnosed at the molecular level by DNA Sequencing technique for analysis of the sequence of the nitrogenous bases of 16S rRNA gene with the global database. The isolated bacteria were characteristic of greyish-white color after 48 hours of growth and appeared as a circular shape, slightly convex and gram-negative. The bacteria were resistant to the antibiotics 20µg/ml Aztreonam. The DNA sequencing technique for analysis of the sequence of the nitrogenous bases of 16S rRNA gene with the global database of the National Center for Biotechnology Information (NCBI) showed that the isolated bacteria was at least 96.22% similar to the species Acinetobacter baumannii As a result, it was recorded for the first time as Acinetobacter sp. AZS1 strain in NCBI. [ABSTRACT FROM AUTHOR]

Livestock farming feed in the northern highlands of Peru is based on the association of ryegrass (Lolium multiflorum L.) ecotype cajamarquino–white clover (Trifolium repens L.) Ladino variety, which constantly varies in its agronomic characteristics and nutritional value due to management considerations and its association with the soil and the animal. The objective of this study was to evaluate yield, plant height, growth rate, tillering, tiller number, spikelets, basal diameter in ryegrass, elongation rate, internode length and decline points in clover over one year. Nutritive value was represented by crude protein (CP), neutral detergent fibre (NDF), in vitro digestibility of dry matter (IVDDM) and metabolisable energy (ME) at three cutting frequencies (30, 45 and 60 days). Better yield (5588 kg DM ha) and plant height (47.1 cm) were shown by the 60-day cutting frequency; however, there was no difference (p > 0.05) between the three cutting frequencies in annual yield. There were no differences between the number of tillers and basal diameter. Clover height, elongation rate and internode length were higher at 60 days. The highest CP concentration and the lowest NDF value (p < 0.05) were achieved by clover at 30 and 45 days. Producers should consider the results when deciding when to use this association in dairy cattle feeding. [ABSTRACT FROM AUTHOR]

Abstract [Objective] Invasion of Trifolium repens occupies the living space of turfgrasses and has been seriously threatening the quality and function of turfs. Examining the impact of T . repens invasion on the functional traits of Poa pratensis and turf quality is helpful for understanding the invasion mechanism of T . repens and for establishing and maintaining gramineous turfgrass. [Methods] Taking the T . repens-invaded P . pratensis turf as object, the sample survey method was employed to investigate the differences in the functional traits and turf quality of P . pratensis under different degrees of T . repens invasion (control, low invasion, moderate invasion, and heavy invasion), and to evaluate turf quality by the membership function method. [Results] (1) With increase in degree of T . repens invasion, the carbon content of P . pratensis organs and the cost of leaf construction, as well as the ratio of carbon to nitrogen, carbon to phosphorus, and nitrogen to phosphorus were gradually decreased, while the specific leaf area and nitrogen and phosphorus content in the organs were increased. (2) At the same invasion level, the carbon, nitrogen, and phosphorus contents in the organs of P . pratensis were higher in leaves than in roots and stems, and the carbon to nitrogen ratio and carbon to phosphorus ratio were higher in roots and stems than in leaves, while the nitrogen to phosphorus ratio was higher in stems and leaves than in roots. (3) The density, texture, greenness index, and uniformity of P . pratensis turf were decreased with increase in T . repens invasion, while the aboveground biomass and belowground biomass were increased. (4) The comprehensive evaluation by the membership function method showed that turf quality was the best without T . repens invasion but the worst under heavy T . repens invasion. Leaf carbon content had the greatest influence on turf quality. [Conclusion] T . repens invasion alters P . pratensis functional traits as well as affects turf quality, landscape, and function.

The reaction of different perennial grasses and legumes to different soil compositions is important for the selection of genotypes suitable for specific pedoclimatic areas where the grasslands are located. To this end, a laboratory experiment was performed to estimate the effect of pH on the germination and initial development of plants of two perennial legume species: Trifolium repens (white clover) - Miorița and Carpatin varieties and Lotus corniculatus (birdsfoot trefoil)-Doru and Magurele 8, varieties. In the experiment 6 pH levels were used: 2.0, 4.0, 5.0, 6.0, 8.0 and 10.0. The rate of seed germination and the subsequent development of the seedlings were determined. Seed germination was influenced by the pH level of the substrate, by the species and also by the cultivar of the same species. Lotus corniculatus was the most tolerant, germinating even on the substrate with pH 2. The biometric measurements performed - the length of the roots and shoots, revealed that Lotus corniculatus had better development of the seedlings to environments with high acidity, the Doru variety being more tolerant. In the case of Trifolium repens, the Carpatin variety had a better seed germination and seedling development on substrates with increased acidity. [ABSTRACT FROM AUTHOR]

It is estimated that up to 50 % of arable lands worldwide are acidic, and most crops are severely inhibited due to the high active aluminum (Al). Trifolium repens is an excellent legume forage with a certain acid tolerance, although it is affected by Al toxicity in acidic soil. In this study, physiological and transcriptomic responses of different white clover varieties were analyzed when exposed to a high-level of Al stress. The results revealed that Trifolium repens had a high level of Al toxicity tolerance, and accumulated nearly 70 % of Al3+ in its roots. Al toxicity significantly inhibited the root length and root activity, decreased the chlorophyll (Chl) content and photosynthetic pigments, while significantly increased the intercellular CO2 concentration (Ci). The content of malondialdehyde (MDA), electrolyte leakage (EL), proline and reactive oxygen species (ROS) were significantly accumulated under Al stress. Furthermore, a total of 27,480 differentially expressed genes (DEGs) were identified after the treatment. Gene ontology (GO) and Kyoto encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that most Al-responsive genes enriched to chloroplast thylakoid membrane, chloroplast stroma and photosynthesis in Haifa leaf while in MAG leaf highly enriched in response to regulation of defense response, which could induce the different tolerance of the two cultivars to Al stress. Besides, pectin methylesterase (PME), glycosyl transferases (GT1) and chalcone synthase genes associated with cell wall biosynthesis may improve the Al accumulation and enhance tolerance of Al toxicity. The results established here would help to understand the morphological structure, physiological and biochemical response, and molecular mechanism of white clover under Al tolerance.

The ability of plants to select effective symbiotic partners is crucial for optimum plant growth. In New Zealand, breeding programmes for white clover (Trifolium repens) have made selections largely based on above-ground characteristics, with little direct attention given to the ability of cultivars to form effective below-ground associations. The ability of three pairs of historical (1930s–1950s), and modern (2000s) cultivars of white clover, to form associations with effective strains of Rhizobium leguminosarum (rhizobia) from a mixture of strains was tested in vitro. First, the efficacy of six individual strains of rhizobia was ranked against all six clover cultivars with shoot biomass used as a direct measure of symbiotic effectiveness for each strain × cultivar combination. Next, each cultivar was inoculated with a mixture of all rhizobia strains at the same cell concentration to examine the identity and frequency of strains found on each host. There was a positive relationship between nodule occupancy and strain effectiveness for historical but not modern cultivars. Cultivars Grasslands Huia and Louisiana (both historical) had nodule occupancy increase with strain effectiveness. This study provides some evidence that historical cultivars may be better able to form associations with effective strains of rhizobia compared with modern cultivars. [ABSTRACT FROM AUTHOR]

White clover (Trifolium repens L.) is an important forage and aesthetic plant species, but it is susceptible to drought and heat stress. The phytohormone auxin regulates several aspects of plant development and alleviates the effects of drought stress in plants, including white clover, by involving auxin/indole acetic acid (Aux/IAA) family genes. However, Aux/IAA genes and the underlying mechanism of auxin-mediated drought response remain elusive in white clover. To extend our understanding of the multiple functions of Aux/IAAs, the current study described the characterization of a member of the Aux/IAA family TrIAA27 of white clover. TrIAA27 protein had conserved the Aux/IAA family domain and shared high sequence similarity with the IAA27 gene of a closely related species and Arabidopsis. Expression of TrIAA27 was upregulated in response to heavy metal, drought, salt, NO, Ca2+, H2O2, Spm, ABA, and IAA treatments, while downregulated under cold stress in the roots and leaves of white clover. TrIAA27 protein was localized in the nucleus. Constitutive overexpression of TrIAA27 in Arabidopsis thaliana led to enhanced hypocotyl length, root length, plant height, leaf length and width, and fresh and dry weights under optimal and stress conditions. There was Improved photosynthesis activity, chlorophyll content, survival rate, relative water content, endogenous catalase (CAT), and peroxidase (POD) concentration with a significantly lower electrolyte leakage percentage, malondialdehyde (MDA) content, and hydrogen peroxide (H2O2) concentration in overexpression lines compared to wild-type Arabidopsis under drought and salt stress conditions. Exposure to stress conditions resulted in relatively weaker roots and above-ground plant growth inhibition, enhanced endogenous levels of major antioxidant enzymes, which correlated well with lower lipid peroxidation, lower levels of reactive oxygen species, and reduced cell death in overexpression lines. The data of the current study demonstrated that TrIAA27 is involved in positively regulating plant growth and development and could be considered a potential target gene for further use, including the breeding of white clover for higher biomass with improved root architecture and tolerance to abiotic stress.

The paper studies the genetic diversity of microorganisms isolated from root nodules of wild populations of the legumes Lathyrus pratensis L., Vicia cracca L., Trifolium repens L., and Astragalus schelichowii Turcz. collected near Norilsk (Arctic Russia). The taxonomic position of the 19 isolates obtained was determined by sequencing the 16S rRNA gene (rrs). The isolates were assigned to four genera of the order Hyphomicrobiales: Rhizobium, Pararhizobium, Bosea and Tardiphaga. Nine fast-growing isolates belonged to the genera Rhizobium and Pararhizobium. ITS region sequencing clarified the species identity of 6 rhizobial isolates. Isolates from V. cracca nodules were identified as Pararhizobium sp., P. herbae. Microsymbionts from T. repens were assigned to Rhizobium sp. and to the species R. beringeri, while isolates from L. pratensis were identified as P. herbae and R. beringeri. Symbiotic nodA and nodC genes were found in the Rhizobium strains P8/5-2, P9/1-1 and P9/3-2 from L. pratensis and T. repens nodules, nodA gene was detected in the Pararhizobium strains P7/3-1, P7/4-1, P7/5-1 from V. cracca nodules. Nine out of ten slow-growing isolates were assigned to the genus Bosea. Three isolates from the nodules of V. cracca were assigned to the species B. psychrotolerans. Six isolates from the nodules of A. schelichowii were identified as B. vaviloviae, B. lathyri and Bosea sp. The strain P22/3-5 isolated from the nodule of A. schelichowii was identified as Tardiphaga robiniae. Simultaneous presence of strains belonging to different genera of the order Hyphomicrobiales was detected in the nodules of V. cracca and A. schelichowii. [ABSTRACT FROM AUTHOR]

Abstract Background White clover (Trifolium repens L.), an excellent perennial legume forage, is an allotetraploid native to southeastern Europe and southern Asia. It has high nutritional, ecological, genetic breeding, and medicinal values and exhibits excellent resistance to cold, drought, trample, and weed infestation. Thus, white clover is widely planted in Europe, America, and China; however, the lack of reference genome limits its breeding and cultivation. This study generated a white clover de novo genome assembly at the chromosomal level and annotated its components. Results The PacBio third-generation Hi-Fi assembly and sequencing methods generated a 1096 Mb genome size of T. repens, with contigs of N50 = 14 Mb, scaffolds of N50 = 65 Mb, and BUSCO value of 98.5%. The newly assembled genome has better continuity and integrity than the previously reported white clover reference genome; thus provides important resources for the molecular breeding and evolution of white clover and other forage. Additionally, we annotated 90,128 high-confidence gene models from the genome. White clover was closely related to Trifolium pratense and Trifolium medium but distantly related to Glycine max, Vigna radiata, Medicago truncatula, and Cicer arietinum. The expansion, contraction, and GO functional enrichment analysis of the gene families showed that T. repens gene families were associated with biological processes, molecular function, cellular components, and environmental resistance, which explained its excellent agronomic traits. Conclusions This study reports a high-quality de novo assembly of white clover genome obtained at the chromosomal level using PacBio Hi-Fi sequencing, a third-generation sequencing. The generated high-quality genome assembly of white clover provides a key basis for accelerating the research and molecular breeding of this important forage crop. The genome is also valuable for future studies on legume forage biology, evolution, and genome-wide mapping of quantitative trait loci associated with the relevant agronomic traits.

Premise: β‐Cyanoalanine synthase (β‐CAS) and alternative oxidase (AOX) play important roles in the ability of plants to detoxify and tolerate hydrogen cyanide (HCN). These functions are critical for all plants because HCN is produced at low levels during basic metabolic processes, and especially for cyanogenic species, which release high levels of HCN following tissue damage. However, expression of β‐CAS and Aox genes has not been examined in cyanogenic species, nor compared between cyanogenic and acyanogenic genotypes within a species. Methods: We used a natural polymorphism for cyanogenesis in white clover to examine β‐CAS and Aox gene expression in relation to cyanogenesis‐associated HCN exposure. We identified all β‐CAS and Aox gene copies present in the genome, including members of the Aox1, Aox2a, and Aox2d subfamilies previously reported in legumes. Expression levels were compared between cyanogenic and acyanogenic genotypes and between damaged and undamaged leaf tissue. Results: β‐CAS and Aox2a expression was differentially elevated in cyanogenic genotypes, and tissue damage was not required to induce this increased expression. Aox2d, in contrast, appeared to be upregulated as a generalized wounding response. Conclusions: These findings suggest a heightened constitutive role for HCN detoxification (via elevated β‐CAS expression) and HCN‐toxicity mitigation (via elevated Aox2a expression) in plants that are capable of cyanogenesis. As such, freezing‐induced cyanide autotoxicity is unlikely to be the primary selective factor in the evolution of climate‐associated cyanogenesis clines. [ABSTRACT FROM AUTHOR]

In addition to improving soil quality, the fertilisation of grassland with cattle slurry is often associated with seed dispersal. Most studies focus on the effects of cattle slurry on the germination and early development of weed species, but less is known about how slurry affects the germination process of grasses and forage legumes. The aim of Experiment I of our study was therefore to investigate the influence of soaking time in cattle slurry of different concentrations on Lolium multiflorum, Dactylis glomerata, Trifolium pratense and Trifolium repens. Seeds were soaked in undiluted (100%) and diluted cattle slurries (50% and 25%) for 14, 28, 42, 56, 70 and 84 days. Experiment II was conducted to study the initial growth of studied plants from seeds soaked in cattle slurry of different concentrations for 14 days. After the germination test, which was carried out under controlled conditions, the germination index (GI) was calculated. The results (Experiment I) show that a short soaking in cattle slurry (14 days) has no negative effect on the germination process for all species. However, a longer soaking resulted in significantly reduced and delayed germination, especially in undiluted slurry for grasses and diluted slurries for clovers. The slurry concentration (Experiment II) only influenced the root growth of L. multiflorum. Seedlings grown from seeds soaked in undiluted slurry had a 17% higher relative root length than the control and developed significantly longer root systems than the other two slurry concentrations. [ABSTRACT FROM AUTHOR]

Mixed-species grassland containing legumes were suggested to increase yield compared to monocultures. Furthermore, some legumes were suggested to be able to sustain growth, even under drought conditions. The first aim of the current study was to measure if multispecies grassland with legumes is also more productive when their N input due to symbiotic N2 fixation is taken into account. Our second aim was to determine the benefit of grass–legume mixtures in terms of dry matter production under naturally occurring drought conditions. Mixed-species grasslands, consisting of monocultures and variable mixtures of (a) Trifolium pratense, (b) Trifolium. repens, (c) Lolium perenne, and (d) a mixture of drought-tolerant grasses (GSWT based), were assessed for their dry matter production over two years with contrasting weather patterns. The legume–grass seeding mixtures received either a fixed (180 kg N ha−1) or adapted N-fertilizer application (0–180 kg N ha−1), with the latter taking the assumed symbiotic N2 fixation by legumes into account. Mixed-species grassland showed improved yield compared to monocultures both in comparably humid and drought-affected years. The benefits of multispecies grass–legume mixtures were considerably more obvious under a fixed but still measurable under an adapted N-fertilizer regime. The species diversity effect appears to be significantly dependent on the additional N supply enabled by legumes’ symbiotic N2-fixation. Legumes and drought-tolerant grasses yielded equally well under drought conditions, although legumes showed major advantages during moderate drought and humid conditions. White and red clover, although both legumes, differed significantly in their persistence under elevated-N and their dry matter production under low-N fertilizer application, but were equal in their tolerance towards drought.

AbstractWhite clover (Trifolium repens L.) is an important legume forage, which is widely distributed in cool-season regions. Therefore, cold stress is a major environmental factor limiting its growth and production, while little is known about the its cold tolerance at molecular level. In the present study, we performed time-course RNA-seq analysis under cold stress. RNA-seq results suggested that genes associated with “oxidoreductase activity” and “transcription regulator activity” are more likely related to the response of white clover to cold stress. To identify the specific gene modules and the hub genes of white clover in response to cold stress, we applied weighted gene co-expression network analyses (WGCNA) to transcriptome data. We also found that gene modules that focus on protein kinase activity, DNA-binding transcription factor activity and oxidoreductase activity, are more likely to be involved in the response of white clover to cold stress. Especially, we identified several AP2/ERF TF genes and CDPK genes as pivotal genes in white clover in response to cold stress, which would provide helpful insights into the molecular mechanisms underlying the response of white clover to cold stress.

Background: White clover (Trifolium repens L.), an excellent perennial legume forage, is an allotetraploid native to southeastern Europe and southern Asia. It has high nutritional, ecological, genetic breeding, and medicinal values and exhibits excellent resistance to cold, drought, trample, and weed infestation. Thus, white clover is widely planted in Europe, America, and China; however, the lack of reference genome limits its breeding and cultivation. This study generated a white clover de novo genome assembly at the chromosomal level and annotated its components. Results: The PacBio third-generation Hi-Fi assembly and sequencing methods generated a 1096 Mb genome size of T. repens, with contigs of N50 = 14 Mb, scaffolds of N50 = 65 Mb, and BUSCO value of 98.5%. The newly assembled genome has better continuity and integrity than the previously reported white clover reference genome; thus provides important resources for the molecular breeding and evolution of white clover and other forage. Additionally, we annotated 90,128 high-confidence gene models from the genome. White clover was closely related to Trifolium pratense and Trifolium medium but distantly related to Glycine max, Vigna radiata, Medicago truncatula, and Cicer arietinum. The expansion, contraction, and GO functional enrichment analysis of the gene families showed that T. repens gene families were associated with biological processes, molecular function, cellular components, and environmental resistance, which explained its excellent agronomic traits. Conclusions: This study reports a high-quality de novo assembly of white clover genome obtained at the chromosomal level using PacBio Hi-Fi sequencing, a third-generation sequencing. The generated high-quality genome assembly of white clover provides a key basis for accelerating the research and molecular breeding of this important forage crop. The genome is also valuable for future studies on legume forage biology, evolution, and genome-wide mapping of quantitative trait loci associated with the relevant agronomic traits. [ABSTRACT FROM AUTHOR]

International seed trading provides a significant introductory pathway for weed seeds, and many globally established weeds originated as contaminants in agricultural seed lots. Management of these trade systems helps minimize agricultural losses and is an important means of preventing future biological incursions. Forage crop seed lots could be considered higher risk than seed lots of arable and vegetable crops, as they have been found to have a higher percentage of contaminated seed lots. Two of the most commonly used temperate forage crops worldwide are perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). New Zealand is one of the top producers of these crop seeds globally, and both species are commonly used in New Zealand pastures. Using historical and current seed lot analytical purity test results, we examined the frequency, identity and temporal changes of weed seeds found within agricultural seed lots of perennial ryegrass and white clover grown in New Zealand from 1912 to 2019. Overall, the percentage of contaminated forage seed lots decreased between approximately three to sixfold over the study period, indicating that herbicide availability, seed certification and improved crop management have been effective for weed control. However, we identified a handful of annual weed species that could become more problematic in the future, either because they showed an increasing presence trend in seed lots or were identified as the most common contaminants. In 2019, Vulpia bromoides was the most common contaminant in perennial ryegrass seed lots, and Chenopodium album was the most common in white clover seed lots. Sherardia arvensis and Poa annua, both significant species with an increasing presence trend, had the largest increases in perennial ryegrass seed lots over the study period. Conversely, Rumex acetosella had the largest presence decline for both crop species. There was a significant difference between the percentage of contaminant species that were grass weeds between study crops, where perennial ryegrass seed lots had approximately four times more grass species than white clover. Considering New Zealand trades crop seed with approximately half of the world's countries and contributes substantially to the global supply of forage seed, our study provides a unique insight into changes of the weed spectrum throughout the seed for sowing system over the last century. [ABSTRACT FROM AUTHOR]

Mixed-species grassland containing legumes were suggested to increase yield compared to monocultures. Furthermore, some legumes were suggested to be able to sustain growth, even under drought conditions. The first aim of the current study was to measure if multispecies grassland with legumes is also more productive when their N input due to symbiotic N2 fixation is taken into account. Our second aim was to determine the benefit of grass–legume mixtures in terms of dry matter production under naturally occurring drought conditions. Mixed-species grasslands, consisting of monocultures and variable mixtures of (a) Trifolium pratense, (b) Trifolium. repens, (c) Lolium perenne, and (d) a mixture of drought-tolerant grasses (GSWT based), were assessed for their dry matter production over two years with contrasting weather patterns. The legume–grass seeding mixtures received either a fixed (180 kg N ha−1) or adapted N-fertilizer application (0–180 kg N ha−1), with the latter taking the assumed symbiotic N2 fixation by legumes into account. Mixed-species grassland showed improved yield compared to monocultures both in comparably humid and drought-affected years. The benefits of multispecies grass–legume mixtures were considerably more obvious under a fixed but still measurable under an adapted N-fertilizer regime. The species diversity effect appears to be significantly dependent on the additional N supply enabled by legumes' symbiotic N2-fixation. Legumes and drought-tolerant grasses yielded equally well under drought conditions, although legumes showed major advantages during moderate drought and humid conditions. White and red clover, although both legumes, differed significantly in their persistence under elevated-N and their dry matter production under low-N fertilizer application, but were equal in their tolerance towards drought. [ABSTRACT FROM AUTHOR]

Context: Plant secondary metabolites are of increasing interest for agriculture due to their diverse beneficial ecological functions. The forage crop white clover (Trifolim repens L.) has been intensively studied for its heritable polymorphism in the production of hydrogen cyanide (HCN), a toxic defense phytochemical. In fodder production, white clover accessions are selected for biomass production, whereby HCN production is an unwanted trait. Aim: Although white clover is a legume crop species of global importance, little is known about the linkage between cyanogenesis and growth traits, in particular in combination with resistance-related phytochemicals, such as flavonoids. We aimed to identify differences in biomass production, estimated leaf flavonoid content, and trait correlations in cyanogenic (HCN-producing) and acyanogenic (not HCN-producing) individuals and accessions of white clover. Methods: We analysed 51 white clover accessions from a German germplasm collection for variability in selected traits: cyanogenesis as equivalent electrode potential, estimated leaf flavonoid content, root and shoot production, leaf area, specific leaf area, and number of leaves produced. Key results: Most accessions considered as cyanogenic were heterogeneous for HCN production. Chemical–morphological trait correlations differed between cyanogenic and acyanogenic plants. Acyanogenic individuals and accessions produced more and larger leaves compared to cyanogenic ones. Within cyanogenic accessions, the higher the HCN level of a plant, the fewer but larger leaves were produced. Conclusions: Our results highlight the variation in HCN production within the selected accessions, which calls for a consistent approach for cyanogenesis-based categorisation. Implication: This study demonstrates the potential of combining phytochemical traits with biomass production in white clover when selecting material in a breeding program. White clover is a widely grown legume and of particular interest as a forage and pasture crop due to its high nutritional value. Besides this, the ability to produce hydrogen cyanide, a toxic chemical compound involved in herbivore defence, represents a trait which entails advantages and disadvantages for agricultural practice. Plants producing this compound differ in growth from those not producing it, indicating the potential to integrate the linkage of this chemical trait with plant growth into future selection for breeding. [ABSTRACT FROM AUTHOR]

Trifolium repens (white trefoil) is an important perennial leguminous species from permanent and artificial pastures. White trefoil is usually cultivated in mixture with a grass species, respectively Lolium perenne because they are forming together a balanced source of forage from nutritional point of view. The research analyses the variation of the seasonal growth of Trifolium repens and Lolium perenne in pure stands and as mixture in the conditions of grazing with sheep and cutting. The research was performed at Research and Development Station for Sheep and Goats Breeding Caransebeș on an albic luvisol, pseudo-gleyic, low acid, moderate provisioned with phosphorus and potassium. The formation, growth and development of Trifolium repens stolons was assessed at every grazing cycle and after every cut. Also, there was assessed the plant height before every cutting or grazing cycle. The experimental factors considered were exploitation mode (cutting, grazing 2 LU/ha and 4 LU / ha) and distance between rows at seeding (12.5 and 25 cm). The assessed features for Trifolium repens were: length of the stolons per plant, number of nodes per stolon and the distance between two nodes per 10 plants from each replicate. Distance between rows hasn’t been influenced by the analysed stolons features. Also, once with the increase of the nodes number decreases the length of an internode, these two features of the stolons being corelated negatively. [ABSTRACT FROM AUTHOR]

White clover (Trifolium repens L.) is a perennial species, it is part of the Fabaceae family, it grows as a creeping, branched perennial plant. It is widespread in a wide range of climates in the temperate and subtropical regions of the northern and southern hemispheres. Sustainable agricultural practices include the use of white clover or legumes to supply nitrogen to the soil in a crop rotation strategy to limit the use of agrochemicals. The species is frequently used as a cover crop, which serves as manure and is also included in mixtures with other forage plants in cattle feed. Several studies have reported the suppressive effects of white clover on weed and disease pressure or unexplained failure of over-seeded grasses in clover-dominated pastures. The polyploidy and genetic diversity of white clover have made it difficult to make rapid progress in genetic and genomic studies. Molecular genetic studies have been carried out for the last quarter of a century, and at the initial stage, segregation, and diversity analyses were performed with restriction fragment length polymorphism (RFLP) markers, random amplified polymorphic DNA (RAPD), and markers by amplified fragment length polymorphism (AFLP). The first linkage map was constructed with 78 SSR and 57 AFLP markers using an F2 mapping population cross between parental inbred lines. A linkage map suggesting homeologous pairing of linkage groups was subsequently reported, which consisted of 493 SSR loci on 16 homeologous linkage groups of 1144 cM. [ABSTRACT FROM AUTHOR]

Biochar has wide application prospects as a good soil conditioner, leguminous plants can fix nitrogen and improve soil available nutrients. However, it is not clear how adding biochar when planting leguminous plants affects soil bacterial community and soil available nutrients. This study investigates the effects of biochar addition on the content of ammonia nitrogen, Olsen-P, and available potassium in northeastern farmland soils under the plantation of Trifolium repens and then compared with the application of organic fertilizer. A 90-day incubation experiment was conducted to compare the changes in the structure and relative abundance of soil microflora under varied biochar additions. It was found that the addition of biochar could affect the structure of the microflora and the available nutrients in the soil. When compared with soil planted with T. repens without the addition of biochar, with the application of 3% biochar increased the content of ammonia nitrogen, Olsen-P, and available potassium in the soil by 31.71%, 21.40%, and 11.51%, respectively. High throughput sequencing revealed that the relative abundance of functional bacteria such as azotobacter, rhizobacteria, and phosphorus solubilizing bacteria in the soil increased with the addition of biochar. Furthermore, the effect was more obvious with the addition of organic fertilizers. The addition of biochar improved the microbial community structure and increased the relative abundance of functional bacteria and the content of available nutrients in the soil. This is expected to reduce the application of chemical fertilizers, thereby protecting the environment and conserving natural resources. [ABSTRACT FROM AUTHOR]

Copyright of Acta Prataculturae Sinica is the property of Acta Prataculturae Sinica Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Transcriptional activity of genes related to ionizing radiation responses in chronically irradiated plant populations at radioactively contaminated territories can be a cost-effective and precise approach for stress response evaluation. However, there are limits to studying non-model plants in field conditions. The work studies the transcriptional activity of candidate genes of adaptation to chronic radiation exposure in plant populations from radioactively contaminated territories of the Chernobyl. In this work, we studied plant species with different sensitivity to acute irradiation: Trifolium repens L., Taraxacum officinale Wigg., and Dactylis glomerata L., sampled in the Chernobyl exclusion zone. The differential expression of several candidate genes of adaptation to chronic radiation exposure in the leaves of these species was analyzed, including homologs of Arabidopsis thaliana genes SLAC1, APX1, GPX2, CAB1, NTRB, PP2-B11, RBOH-F, HY5, SnRK2.4, PDS1, CIPK20, SIP1, PIP1, TIP1. All studied species were characterized by upregulation of the CAB1 homolog, encoding chlorophyll a/b binding protein, at radioactively contaminated plots. An increase in the expression of genes associated with water and hydrogen peroxide transport, intensity of photosynthesis, and stress responses (homolog of aquaporin TIP1 for T. repens; homologs of aquaporin PIP1 and transcription factor HY5 for D. glomerata; homolog of CBL-interacting serine/threonine protein kinase CIPK20 for T. officinale) was revealed. The methodological approach for studying gene expression in non-model plant species is described, which may allow large-scale screening studies of candidate genes in various plant species abundant in radioactively contaminated areas. [ABSTRACT FROM AUTHOR]

This study was carried out to determine the effectiveness of some herbicides on weed species and weed population in the landscape area of Iğdır University Şehit Bülent Yurtseven Campus in 2021. In the study, herbicides with active ingredients, 2,4-D amine, Bromoxynil + MCPA, 2,4-D tri-isopropyl amine salt + Picloram, dicamba + triasulfuron, 2,4-D EHE + florasulam, Halosulfuron-methyl and Fluazifop-p-butyl as well as Bromoxynil + MCPA + dicamba + triasulfuron and 2,4-D amine + Fluazifop-p-butyl herbicide mixtures were used. The percentage effects of the herbicides applied in the study on weed dry weights, weed species, and the percentage effects of herbicides on these weed species were determined according to the 3 counts made at certain intervals for the weed species with a density of 1 weeds/m2 and above in the census.As a result of the study, a total of 14 weed species belonging to 8 families were determined in the trial area. Of these detected weed species, Trifolium repens L. (5.49 weed/m2), Cynodon dactylon (L.) Pers. (3.24 weed/m2), Trifolium pratense L. (1.23 weed/m2), Melilotus albus Medik. (1.07 weed/m2) and Convolvulus arvensis L. (1.03 weed/m2), the density of 5 of them was determined as 1 weeds/m2 and above. As a result of the study, the lowest weed dry weights (2.12 g/m2) and the highest percentage effect (94.50%) were obtained in the 2,4-D tri-isopropyl amine salt + Picloram plots. The percentage effects of the herbicides applied in the study on the weed species varied according to the weed species and the herbicides used.

Introduction Turfgrasses, as one of the important components of urban landscapes, have played a vital role in this regard. However, the main problems of turfgrass development are the cost of turfgrass seeds, maintenance costs such as moving, as well as the high water requirement in arid and semi-arid regions. Thus, the reduction of lawn culture in the landscape is one of the decision has taken in parks and green spaces organization of Tehran, Isfahan and even Mashhad. For over ten years, researchers have been looking for alternatives to conventional grass lawns to reduce the high cost of maintenance especially irrigation cost in urban landscapes. According to many researches, one of the potential ground cover alternatives that might be used instead of turfgrass is White Clover. Clover (Trifolium spp.) from Fabaceae family is a genus of about 300 species. Materials and Methods The aim of this experiment was to compare three common turfgrasses with two clover varieties as turf replacement to reduce landscape maintenance cost specially moving cost. So, some growth and qualitative factors of clover lawn: Trifolium repens var. Calway and Trifolium repens var. Pipolina (micro clover) and three turfgrasses of Festuca arundinacea L. and Lolium perenne L. and commercial sport turf mixture (from NAk-Nederland Ltd.) were compared together. This research was conducted in randomized complete block design with three replications in the research field of the Department of Horticultural Science and Landscape Engineering‚ Faculty of Agricultural‚ Ferdowsi University of Mashhad‚ Mashhad‚ Iran, during 2016 and 2017. The site (59º 38′ E and 36º 16 ′ N; elevation 989 m) is located in an arid and semi- arid region with mean annual rainfall 233.8 mm and long term averages of maximum and minimum temperature are 22.5 ºC and 9.3 ºC‚ respectively. Turfgrass plots were established by directly sowing the seeds in April, 2016. The planting rate of the seedling considering their pure live seeds (PLS) were 45 g.m-2 for Lolium perenne, 34 g.m-2 for Festuca arundinacea, 6.5 g.m-2 for Trifolium repens, 5.5 g.m-2 for micro clover and 39 g.m-2 for commercial mixture of sport turf. The plots were 1 m2 (1m×1m) in size and were prepared after plowing and leveling the soil. The seeds were hand sown and covered with a thin layer of leaf compost and sand. Results and Discussion According to the results in the first evaluation of emergence percentage, Lolium perenne had the highest emergence percentage. After 36 days from culture, all plants had 92-98 % coverage which did not have any significant difference among grasses with clover lawns. In terms of density, uniformity and weed density, there was no significant difference between the studied plants. In the other hands, white clover showed the best quality after clipping in both years. At the point of growth index, which have done in this experiment by measuring height and dry weight of clipping, grass lawns had the higher growth index in compered to clover lawn in both years. Festuca arundinacea and Lolium perenne had the highest growth index and white and micro clover had the lowest growth. Also, with air warming, Festuca arundinacea became dominated plant in height and clipping dry weight. In July, Festuca arundinacea produced the highest clipping dry weight by 40 gr.m-2, Lolium perenne (19.52), commercial sport turf (15.68), white clover (6.24) and micro clover (0.36) gr.m-2. Conclusion One of the problems of landscape is reduction of maintenance costs such as mowing. So, the low growth of white and micro clover is a positive factor in reduction of the moving costs than turfgrasses. Also, the coverage and proper density of clover lawns are similar to grass lawns and did not have a significant difference with them. The character of low growth can be effective in reduction of irrigation costs in white and micro clover, which requires more research and examination in future. This is a positive point in the white clover and micro clover that do not need to move or cut every months. Almost, clover moving is recommended for removing their flower. Therefore, it is recommended to use white and micro clover as a replacement with less maintenance costs in landscape. Finally, the results of cultivation of grass and clover as monoculture in this study can be used to produce clover-grass mixtures suitable for the climate of our country (arid and semi-arid regions), instead of importing turf mixtures from European countries.

• Trifolium repens is a green alternative to toxic corrosion inhibitors. • The inhibitor achieves 98 % inhibition efficiency at 20 ppm in 3.5 % NaCl medium and acts as a mixed-type inhibitor with a strong cathodic effect. • The corrosion inhibition mechanism is driven by physical adsorption of the inhibitor onto the metal surface, following the langmuir adsorption isotherm. • Trifolium repens forms a protective layer which is confirmed by electrochemical and surface analyses. Material degradation is a major issue that has been the subject of intense research and investigation by the scientific community. It has harmful consequences that require serious and careful intervention. However, restrictions on the use of inhibitors containing toxic compounds pose a significant challenge to the implementation of effective corrosion treatments. This has necessitated a continuous search for new and innovative ways to protect against material damage. Plant-derived natural inhibitors offer several advantages, including potent inhibitory effects, lack of toxicity, biodegradability, and environmentally sustainable origins. The purpose of this research was to evaluate the corrosion resistance of API5LX60 carbon steel in a 3.5 % NaCl environment using Trifolium repens as an environmentally friendly inhibitor. The inhibitor extract was analysed using Fourier Transform Infrared (FTIR) spectroscopy. However, gravimetry and electrochemical methods (potentiodynamic polarization and electrochemical impedance spectroscopy (EIS)) were used to investigate the corrosion behaviour. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to examine the surface morphology. After testing a range of concentrations in a 3.5 % NaCl medium, the highest level of inhibition (98 %) was obtained at 20 ppm, confirming the mixed action of the inhibitor with predominantly cathodic action. The inhibition mechanism involved physical adsorption on metal surfaces according to the Langmuir model, which enhances the corrosion-inhibiting ability; the extract forms a protective layer that successfully inhibits corrosion, as confirmed through electrochemical and surface analysis. These results demonstrate that the extract acts as a potent anticorrosive agent. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract Introduction Globally, soil‐borne plant pathogens are a significant contributor to plant yield loss in agricultural systems, including pasture production. The extent of soil biological constraints in high‐value dairy systems was assessed across three major dairying regions of New Zealand. Materials and Methods Regional measures of disease pressure were obtained by comparing white clover, perennial ryegrass and plantain growth in 30 farm soils with (non‐pasteurised) or without (microwave pasteurised) their normal complement of microbial and nematode pathogens. Results Pasteurising soils from the Waikato region led to significant average increases in clover (35%) and ryegrass (19%) shoot dry matter. Individual site yields increased up to 74% for clover and 38% for ryegrass. For Canterbury and Southland, there was no increase in plant yield with pasteurisation on a regional basis, but increases in either clover or ryegrass were significant at three individual farm sites. Across all regions, negative linear relationships between disease pressure (% growth change) and a proxy of soil organic matter quality (anaerobically mineralizable nitrogen:total nitrogen ratio were found for both clover and ryegrass, accounting for 34% of the variation in both clover and ryegrass growth. A positive linear relationship was found between disease pressure and Heterodera cyst nematode abundance, accounting for 33% and 17% of the variation in clover and ryegrass growth change, respectively. The most prevalent putative fungal and oomycete pathogens isolated from the roots and stem bases of clover and ryegrass seedlings were Fusarium oxysporum, Fusarium culmorum, and various Pythium species. Conclusion Our results suggest that root pathogens on New Zeland dairy farms are most prevalent and damaging in the Waikato region where economic modelling estimated clover and ryegrass root disease to cost 211 kg MS ha−1 year−1 in milk production and $909 ha−1 year−1 in farm profitability. Given the scale of these costs, targeted management of soil borne disease could present an economically viable approach to improving the resilience of these multi‐plant multi‐pathogen ecosystems.

● Application of plant defense inducers against tea diseases. ● Application of natural enemies against insect pests. ● Application of Trifolium repens against weeds. The application and development of ‘green’ preventive technologies in tea plantations is an important means of ensuring tea quality and ecological safety. Ecological, agronomic and biological controls are the main preventive measures used in Guizhou Province. This paper summarizes the ‘green’ preventive technologies being applied in Guizhou tea plantations, including the use of plant defense inducers to regulate tea plant responses to pathogens, natural enemies to control pest species causing damage to shoots and Trifolium repens to control the main weed species. In addition, it summarizes the integrated ‘green’ preventive technologies being used in Guizhou and provides a foundation for the ecological maintenance of tea plantations.

Background and objectives: In Iran, as in other countries, social and economic factors have led to land use changes depending on regional conditions. The Taleghan watershed, due to its proximity to population centers such as Tehran and Karaj, construction of the Taleghan Dam in 2001, and becoming a tourist center, has undergone significant changes. Many studies have been conducted to evaluate land use changes in this area, but these studies have investigated changes only until the time of dam water withdrawal in 2005 or until 2016 at most. Thus, this research investigates and analyzes land use changes in the Taleghan watershed over a period of thirty years (1987-2017). Methodology: The study focuses on land use changes in the middle Taleghan watershed. A land use map was prepared for the last thirty years (1987, 1998, 2008, and 2017) using Landsat satellite imagery. The hybrid classification method (a combination of supervised and unsupervised methods) was used, and accuracy was measured using Kappa and overall accuracy, yielding acceptable results in percentages. The T index was used to calculate land use changes. Results: The study shows that the abandoned dryland area (12.08%) is the largest after pasture land use (71.06%). The area of villa construction increased, while the garden area decreased over the thirty-year period. The T index calculation reveals that barelands experienced the most changes during the thirty-year period. Conclusion: Spatial patterns of land use changes were estimated using spatial statistics and the calculation of the share of changes in various land uses. Location quotients were used to analyze the data, and it was calculated for the land uses that experienced the most changes in each subwatershed in 1987, 1998, 2008, and 2017. The results of the LQ show that the rangeland area was almost constant during the period of 1987-2017. The areas of irrigated and rainfed agriculture fluctuated due to emigration and immigration during this period. The area of residential land also increased significantly due to the construction of villas and promenades around the lake by indigenous and non-indigenous people. Investigating the variations of the spatial pattern of different land uses revealed that the most changes occurred in the sub-watershed around the dam lake and the main river. [ABSTRACT FROM AUTHOR]

Copyright of Tropical Grasslands / Forrajes Tropicales is the property of International Centre for Tropical Agriculture - CIAT and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

There is increasing evidence that environmental change associated with urbanization can drive rapid adaptation. However, most studies of urban adaptation have focused on coarse urban vs. rural comparisons or sampled along a single urban–rural environmental gradient, thereby ignoring the role that within‐city environmental heterogeneity might play in adaptation to urban environments.In this study, we examined fine‐scale variation in the presence of hydrogen cyanide (HCN)—a potent anti‐herbivore defence—and its two underlying genes (Ac and Li) between park green spaces and surrounding suburban habitats for five city parks in the Greater Toronto Area.We show that fine‐scale urbanization has driven the formation of micro‐clines in HCN on a scale of <2 km, though the presence and strength of micro‐clines varied across parks. Interestingly, these micro‐clines were driven by lower HCN frequencies inside park green spaces, and are therefore in the opposite direction to that predicted based on previously described patterns of HCN frequency change along urban–rural gradients.Synthesis: These results suggest larger scale, adaptive urban–rural clines occur across a complex matrix of environmental heterogeneity within cities that drives fine‐scale adaptive microclines of varying strengths and directions. [ABSTRACT FROM AUTHOR]

Heat shock transcription factors (HSF) are divided into classes A, B and C. Class A transcription factors are generally recognized as transcriptional activators, while functional characterization of class B and C heat shock transcription factors have not been fully developed in most plant species. We isolated and characterized a novel HSF transcription factor gene, TrHSFB2a (a class B HSF) gene, from the drought stress-sensitive forage crop species, white clover (Trifolium repens). TrHSFB2a was highly homologous to MtHSFB2b, CarHSFB2a, AtHSFB2b and AtHSFB2a. The expression of TrHSFB2a was strongly induced by drought (PEG6000 15% w/v), high temperature (35 °C) and salt stresses (200 mM L−1 NaCl) in white clover, while subcellular localization analysis showed that it is a nuclear protein. Overexpression of the white clover gene TrHSFB2a in Arabidopsis significantly reduced fresh and dry weight, relative water contents (RWC), maximum photosynthesis efficiency (Fv/Fm) and performance index on the absorption basis (PIABS), while it promoted leaf senescence, relative electrical conductivity (REC) and the contents of malondialdehyde (MDA) compared to a wild type under drought, heat and salt stress conditions of Arabidopsis plants. The silencing of its native homolog (AtHSFB2a) by RNA interference in Arabidopsis thaliana showed opposite trends by significantly increasing fresh and dry weights, RWC, maximum photosynthesis efficiency (Fv/Fm) and performance index on the absorption basis (PIABS) and reducing REC and MDA contents under drought, heat and salt stress conditions compared to wild type Arabidopsis plants. These phenotypic and physiological indicators suggested that the TrHSFB2a of white clover functions as a negative regulator of heat, salt and drought tolerance. The bioinformatics analysis showed that TrHSFB2a contained the core B3 repression domain (BRD) that has been reported as a repressor activator domain in other plant species that might repress the activation of the heat shock-inducible genes required in the stress tolerance process in plants. The present study explores one of the potential causes of drought and heat sensitivity in white clover that can be overcome to some extent by silencing the TrHSFB2a gene in white clover. [ABSTRACT FROM AUTHOR]

【Objective】The flower color of plant was mainly determined by anthocyanins that were regulated by dihydroflavonol 4-reductase (DFR), a key regulatory enzyme in the biosynthetic pathway of anthocyanins. It was important for white clover breeding to explore TrDFR properties and its role in the formation of white clover flower color. 【Method】The petals from the wild-type and red-flowered white clover were used as materials to clone the TrDFR sequence, and the bioinformatics analysis and tissue expression analysis were carried out.【Result】The open reading frame of TrDFR sequence was 969 bp in length, encoding 322 amino acids. The molecular weight of DFR protein in white clover mutant was 36.59 kD, which showed an unstable hydrophilic non-secreted protein. The secondary structure was mainly α-helix and random coil, indicating the closest evolutionary relationship with red clover. Tissue expression analysis demonstrated that TrDFR gene was abundantly expressed in petals, petioles and pedicels of white clover, and the expression levels in stems and petals of red flower mutant were significantly higher than those in wild type (P<0.01). 【Conclusion】The gene TrDFR could be involved in the biosynthesis of anthocyanins in white clover petals, which provided a theoretical basis for further research on the functional mechanism of TrDFR in white clover. [ABSTRACT FROM AUTHOR]

Objective. To evaluate the botanical composition of grasslands of kikuyu (Cenchrus clandestinus) compared to tall fescue (Lolium arundinaceum cv. Cajun II), each one in association with white clover (Trifolium repens cv. Ladino), in two independent experiments conducted during two seasons, autumn 2018 and winter 2019. Methodology. Two independent experiments under small-scale milk production system (SMPS) were established in the municipality of Aculco, State of Mexico, during autumn 2018 and winter 2019. The botanical composition of grasslands under intensive continuous grazing by breeding cows was evaluated. One grassland planted with tall fescue cv. Cajun II and the other invaded by kikuyu; each grassland was associated with white clover cv. Ladino. The botanical composition of both experiments was analyzed using a complete randomized experimental design. Results. The kikuyu grassland recorded significant differences (p<0.05) with a higher proportion of forage during the winter 2018. Whereas the tall fescue cv. Cajun II grassland recorded a proportion of forage (p<0.05) higher than its proportion of dead tissue during autumn 2019. Study Implications: The study of the botanical composition of mixed grasslands destined for livestock grazing allows to identify, propose and define strategies for forage production facing agroclimatic and management conditions in order to generate a better and higher forage yield. Conclusions: The proportion of kikuyu was higher than that of tall fescue cv. Cajun II during the two seasons and years evaluated. This highlights the adaptability of kikuyu grass under agroecological conditions such as the absence of rains and high temperatures, coupled with the high stocking densities of the milk production systems in the study region. [ABSTRACT FROM AUTHOR]

One of the most efficient measures that contributes to forage improvement is represented by the temporary pastures consisted of legumes and perennial gramineae. Beside Agrostis tenuis, Festuca rubra is the forage gramineae with the largest spread and dominance in our country. That is why its introduction in various associations with forage legumes leads to qualitative and quantitative improvement of the yields obtained on temporary pastures.

The amount of N species of perennial legumes fixed for each harvest and the total annual crop was assessed on a 2-year period, in a mixture with Festuca arundinaceea. There are using different nitrogenous fertilizer levels: N0; N50; N100; N150. The amount of biological N is positively correlated with the percentage of participation of legumes. During the growing, amount of N increases from cycle I (CI) towards cycle III (CIII), being registered for CI - 15 % N, CII - 32% N and CIII - N 53% of the total nitrogen fixed of species Trifolium repens. For Trifolium pratense and Lotus corniculatus species, the maximum amount of N fixed is achieved at CII, registering a distribution harvest cycles thus 28% N - CI, 40% N - CII and 32% N-CIII for Trifolium pratense , 25 % N - CI, 45 % N - CII and 30 % N - CIII for Lotus corniculatus. The annual amount of N fixed averaged 85 kg / ha in Trifolium repens, 210 kg / ha in Trifolium pratense and 68 kg / ha in Lotus corniculatus. The fertilization with nitrogen at level of 100 and 150 kg / ha negatively influenced symbiotic nitrogen fixation in Trifolium repens and Lotus corniculatus species.

The main objective of this study was to investigate whether the most common wild plant species of urban grassland can be used for phytoremediation of soils polluted with heavy metals. The study was conducted in the city of Varaždin, in northern Croatia. The content of heavy metals (Cd, Cu, Fe, Mn, Ni, Pb, Zn) was determined in soil samples as well as in unwashed and washed plant samples (Taraxacum officinale, Plantago lanceolata, Trifolium repens). The results show that the most polluted site is the railway station, while most sites are polluted by road traffic. The soils are most enriched with Pb, Cu, Zn and Cd. The bioconcentration factors for all three plant species are <1, indicating the relatively low capacity of phytoextraction. A considerable amount of heavy metals is found in the dust deposited on the plant surface, which is confirmed by a statistically significant difference between washed and unwashed plant samples. In addition, the biomass of each plant species that can be removed (in t/ha year), the mass of specific heavy metal that can be removed (in kg/ha), and the years required for phytoremediation are reported. In conclusion, phytoremediation with only common plant species of urban grassland is not possible within a reasonable period of time. [ABSTRACT FROM AUTHOR]

Leaves are the primary and critical feed for herbivores. They directly determine the yield and quality of legume forage. Trifolium repens (T. repens) is an indispensable legume species, widely cultivated in temperate pastures due to its nutritional value and nitrogen fixation. Although the leaves of T. repens are typical trifoliate, they have unusual patterns to adapt to herbivore feeding. The number of leaflets in T. repens affects its production and utilization. The KNOX gene family encodes transcriptional regulators that are vital in regulating and developing leaves. Identification and characterization of TrKNOX gene family as an active regulator of leaf development in T. repens were studied. A total of 21 TrKNOX genes were identified from the T. repens genome database and classified into three subgroups (Class I, Class II, and Class M) based on phylogenetic analysis. Nineteen of the genes identified had four conserved domains, except for KNOX5 and KNOX9, which belong to Class M. Varying expression levels of TrKNOX genes were observed at different developmental stages and complexities of leaves. KNOX9 was observed to upregulate the leaf complexity of T. repens. Research on TrKNOX genes could be novel and further assist in exploring their functions and cultivating high-quality T. repens varieties. [ABSTRACT FROM AUTHOR]

Tailings that are generated by gold mining activities are frequently abandoned to let nature initiate ecological succession processes. Given the slowness of natural processes, colonization mechanisms could be accelerated through assisted revegetation with herbaceous species as pioneer species prior to reintroduction of native woody species to stabilize them and reduce their transport in the environment. Application of biochar increasingly has been suggested as a means of supporting germination, emergence and growth of seedlings on mine tailings. In this study, we assessed the effects of two types of biochar on the germination and growth of Avena sativa, Festuca rubra and Trifolium repens that were hydroseeded onto waste rock and fine tailings from gold mining. The first biochar was made through pyrolysis of maple bark at 700 °C and the second biochar was derived from pyrolysis of hardwood chips (< 75% sugar maple), at temperatures of 500 °C. Seeds were placed separately on fine and waste rock tailings in 9-cm diameter Petri dishes and the germination test was conducted in a growth chamber. The growth mesocosm experiment was conducted in the greenhouse, where the three plant species were mixed in two hydroseeding ratios. In petri-plate tests, biochar application improved the germination of plant species, depending upon the type of biochar and plant species. Avena sativa best responded to biochar application, with the highest germination rate (up to 94%). In the greenhouse, plant growth in hydroseeding mixtures was also affected by biochar type. The first biochar (Award-Maple-700) enhanced root and aboveground biomass of plants in hydroseeding mixtures compared to the level without biochar. It also enhanced aboveground biomass of Festuca rubra and Trifolium repens individually compared to the level without biochar. However, the second biochar did not consistently enhance the growth of species. On one hand, these results underscore the potential for biochar to improve initial revegetation of mining residues using herbaceous species; on the other hand, its effect varies with both the type of biochar and plant species. Larger, longer term studies are recommended to test observed effects in situ, with the aim of revegetating gold mining tailings at operational scales.Article Highlights: Two biochar with different physicochemical properties were compared for their effects on germination and growth of three herbaceous species on gold mine tailings. One of the biochar stood out, with a marked effect on plant germination and productivity. We show that the application of biochar as amendment for revegetation of mine tailings can be very beneficial for plant growth, provided that the appropriate type of biochar is carefully selected. [ABSTRACT FROM AUTHOR]

Ecological interactions between flowers and pollinators greatly affect the reproductive success. To facilitate these interactions, many flowers are known to display their attractive qualities, such as scent emission, flower rewards and floral vertical direction, in a rhythmic fashion. However, less is known about how plants regulate the relationship between these flower traits to adapt to pollinator visiting behavior and increase reproduction success. Here we investigated the adaptive significance of the flower bending from erect to downward in Trifolium repens. We observed the flowering dynamic characteristics (changes of vertical direction of florets, flowering number, pollen grain numbers, pollen viability and stigma receptivity over time after blossom) and the factors affecting the rate of flower bending in T. repens. Then we altered the vertical direction of florets in inflorescence of different types (upright and downward), and compared the pollinator behaviors and female reproductive success. Our results showed that florets opened sequentially in inflorescence, and then bend downwards slowly after flowering. The bending speed of florets was mainly influenced by pollination, and bending angle increased with the prolongation of flowering time, while the pollen germination rate, stigma receptivity and nectar secretion has a rhythm of "lowhigh-low" during the whole period with the time going. The visiting frequency of all the four species of pollinators on upward flowers was significantly higher than that of downward flowers, and they especially prefer to visit flowers with a bending angle of 30°-60°, when the flowers was exactly of the highest flower rewards (nectar secretion and number of pollen grains), stigma receptivity and pollen germination rate. The seed set ratio and fruit set ratio of upward flowers were significantly higher than downward flowers, but significantly lower than unmanipulated flowers. Our results indicated that the T. repens could increase female and male fitness by accurate pollination. The most suitable flower angle saves pollinators' visiting energy and enables them to obtain the highest nectar rewards. This coordination between plants and pollinators maximizes the interests of them, which is a crucial factor in initiating specialized plant-pollinator relationships. [ABSTRACT FROM AUTHOR]

It is estimated that up to 50 % of arable lands worldwide are acidic, and most crops are severely inhibited due to the high active aluminum (Al). Trifolium repens is an excellent legume forage with a certain acid tolerance, although it is affected by Al toxicity in acidic soil. In this study, physiological and transcriptomic responses of different white clover varieties were analyzed when exposed to a high-level of Al stress. The results revealed that Trifolium repens had a high level of Al toxicity tolerance, and accumulated nearly 70 % of Al3+ in its roots. Al toxicity significantly inhibited the root length and root activity, decreased the chlorophyll (Chl) content and photosynthetic pigments, while significantly increased the intercellular CO 2 concentration (Ci). The content of malondialdehyde (MDA), electrolyte leakage (EL), proline and reactive oxygen species (ROS) were significantly accumulated under Al stress. Furthermore, a total of 27,480 differentially expressed genes (DEGs) were identified after the treatment. Gene ontology (GO) and Kyoto encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that most Al-responsive genes enriched to chloroplast thylakoid membrane, chloroplast stroma and photosynthesis in Haifa leaf while in MAG leaf highly enriched in response to regulation of defense response, which could induce the different tolerance of the two cultivars to Al stress. Besides, pectin methylesterase (PME), glycosyl transferases (GT1) and chalcone synthase genes associated with cell wall biosynthesis may improve the Al accumulation and enhance tolerance of Al toxicity. The results established here would help to understand the morphological structure, physiological and biochemical response, and molecular mechanism of white clover under Al tolerance. [Display omitted] • Trifolium repens roots accumulated most Al and localized mainly in cell wall. • Many genes involved in metal chelation were identified to be Al-induced DEGs. • Organic acid play an important role in Al tolerance of Trifolium repens. [ABSTRACT FROM AUTHOR]

Pollen abnormalities frequency of Scots pine and pollen sterility of white clover, common columbine, and greater celandine growing in the Bryansk and Gomel' regions radioactively contaminated after the accident at the Chernobyl nuclear power plant (NPP) were assessed. The frequency of abnormal pine pollen at the most contaminated plots significantly exceeded the control level and positively correlated with the total absorbed dose and the absorbed dose from β -radiation. No sustainable significant changes in pollen sterility of the herbaceous plants studied were found in the exclusion zone of the Chernobyl NPP. • Pine abnormal pollen frequency, in some cases, increased near the Chernobyl NPP. • Frequency of pine abnormal pollen positively correlated with the absorbed dose. • Radiation levels near the ChNPP did not induce steady changes in pollen sterility. [ABSTRACT FROM AUTHOR]