Clover Species Research Articles

Source of variation of isoflavone concentrations in perennial clover species.

Introduction:Clover has attracted considerable interest not only as a valuable livestock forage plant, but also as an important source of isoflavones. The current study was aimed to assess the variation of concentration of three isoflavones in clover species grown under a cool temperate climate environment in Lithuania.Materials and Methods:Isoflavone contents were quantified in the plant parts of 21 accessions belonging to five perennial species of genus Trifolium (T. pratense, T. repens, T. medium, T. rubens, and T. pannonicum). Daidzein, formononetin, and genistein concentrations were quantified in separate plant parts by reversed-phase high-performance liquid chromatography. The analyte extraction was performed from dried and ground leaves, stems, flowers, and roots. The procedure included acid hydrolysis of isoflavone glycosides to aglycones.Results:According to the averaged sum of the three isoflavones quantified in leaves-stems-flowers, the five clover species ranked as follows: T. medium (7.54-3.62-2.31 mg/g) >T. pratense> T. rubens> T. pannonicum> T. repens (0.191-0.204-0.171 mg/g). The contribution of individual compound to the total isoflavone content depended on the species, accession, and plant part. The major part of the isoflavones is concentrated in leaves or stems; however, there is a great variation also.Conclusion:There exists a large variation in the total as well as in individual concentration of isoflavones among the clover species and plant parts and within species. With regard to isoflavone concentration and variability within species, some accessions of T. medium and T. pratense can be considered a highly promising source of phytoestrogens.

Reproductive development of four top flowering annual clovers

A series of field experiments aimed to quantify reproductive development of four clover species, arrowleaf (Trifolium vesiculosum), balansa (T. michelianum), gland (T. glanduliferum) and Persian (T. resupinatum), for introduction to New Zealand dryland pastures. The duration from emergence to flowering was related to the length of, and direction of change in, photoperiod at the time of first trifoliate leaf appearance. Autumn-sown crops that emerged into a decreasing photoperiod had a longer vegetative growth before they turned reproductive. The time to flower became shorter with increasing photoperiod until the longest day of the year, before it began to slow down as photoperiod decreased towards late summer. Prima gland clover flowered earlier (500–1216 degree-days) than Bolta balansa (600–1733 degree-days), Cefalu arrowleaf (940–1834 degree-days) and Mihi Persian (1047–2610 degree-days) clovers. The duration from pollination to physiological maturity was 274–689 degree-days for Cefalu, 185 degree-days for Bolta, 256 degree-days for Prima, and 425 degree-days for Mihi. The differences in flowering time suggests the suitability of Prima gland clover for areas that dry out quickly in late spring, Bolta balansa clover for areas of wet winter and dry summer, and Cefalu arrowleaf and Mihi Persian clovers for areas that receive higher spring rainfall.

Distribution data on the family Melittidae (Hymenoptera) of Turkey with considerations about their importance as pollinators

The examination of specimens collected from various parts of Turkey, mainly from East Anatolia, and an overview of the literature allows us to reach the conclusion that the Melittidae of Turkey are represented by 3 genera, Dasypoda (14 species), Macropis (2 species), and Melitta (9 species), with a total of 25 species including Dasypoda toroki Michez, 2004, a new record for the Turkish fauna. Dasypoda hirtipes (Fabricius, 1793), Melitta (Melitta) leporina (Panzer, 1799), and M. dimidiata Morawitz, 1876 are the most widespread and abundant species. Dasypoda friesana Schletterer, 1890; D. longigena Schletterer, 1890; D. patinyi Michez, 2002; D. visnaga (Rossi, 1790); Melitta rasmonti Michez, 2007; M. nigricans Alfken, 1905; M. singular Michez, 2012; M. haemorrhoidalis; and M. melanura (Nylander, 1852) are very rare species and most are known from one locality only. The rest of the species are moderately distributed in Turkey. Five species of Dasypoda and 3 species of Melitta have type localities from Anatolia; of these, D. longigena, M. bicollaris, M. singular, M. rasmonti, and D. warnckei are endemic to Anatolia. New distribution areas were added for each species and the plant species visited were included. Although the genus Dasypoda visits mostly wild flowers, D. hirtipes also frequently visits sunflowers and it is an important pollinator of this plant. In the case of the genus Macropis, females collect oil and pollen from the flowers of Lysimachia (Primulaceae) as larval food. Melitta leporina, M. dimidiata, and M. bicollaris are important pollinators of fodder crops, such as alfalfa, sainfoin, and various clover species and some other legumes.

Productivity and seedling recruitment of naturalised annual clovers versus sown clovers Trifolium repens and Trifolium subterraneum

Abstract Naturalised annual clover (NAC) species (suckling clover, cluster clover, striated clover, and haresfoot clover) are commonly present to locally abundant in summer dry hill and high country areas where white and subterranean (sub) clover abundance is limited. This field trial investigated NAC species dry matter production and seedling regeneration compared to white and sub clover. Autumn seedling recruitment was measured in response to low (75 kg/ha) or high (200 kg/ ha) superphosphate (SP) application. Over two growing seasons, NAC species contributed >90% to pasture legume content while white and sub clover contributed

Phosphorus Inflow into Two Species of Clover Root with Different Morphology Colonized by AM Fungi

The effects of arbuscular mycorrhizal (AM) fungi on growth and phosphorus (P) inflow into two species of clover plant with different root morphology were studied. The experiment was arranged as a randomized complete block design consisting of a 2×3×3 factorial combination of two clover species (Trifolium alexandrinum L. and Trifolium pratense L.), three mycorrhiza states (without mycorrhiza, Glomus intraradices and Glomus mosseae) and three harvests (20, 40 and 60 days after transplanting) with 4 replications. In this experiment, plant dry matter, root colonization and P uptake in terms of P inflow and mycorrhizal P response (MPR) were determined. Results showed that mycorrhizal growth response (MGR) of T. alexandrinum was greater than that of T. pratense. This was mainly attributed to the higher root length of T. alexandrinum which provides a greater surface area for colonization compared to T. pratense. The highest P inflow was observed during the first harvest period (0-20 d). In this harvest period and during the treatment with T. alexandrinum, P inflow into non-colonized roots, roots colonized by G. mosseae and G. intraradices were 1.9, 6.8 and 8.01 pM m-1 s-1, respectively being 3.6 and 4.2 times greater than the control plants. The greater effect of G. intraradices compared to G. mosseae on increasing P inflow might be due to the superior ability of G. intraradices to spread into the soil and absorb more P beyond the P depletion zones around the roots and/or might be due to the higher intensity of arbuscules and intra-radical hyphae per unit length of colonized root. In conclusion, T. alexandrinum was more responsive to mycorrhizal colonization than T. pratense which, in turn, resulted in better P nutrition of T. alexandrinum colonized by G. intraradices.

Thermal time requirements for germination of four annual clover species

Germination of ‘Cefalu’ arrowleaf, ‘Bolta’ balansa, ‘Prima’ gland and ‘Mihi’ Persian clovers was determined from constant temperature (5–40 °C) from incubator experiments. A ‘broken stick’ regression of germination rates against temperature was used to quantify thermal time (Tt) requirements and cardinal (base, optimum and maximum) temperatures. Tt requirements for 75% germination were higher for ‘Cefalu’ arrowleaf (34 °Cd) than ‘Bolta’ balansa (32 °Cd), ‘Prima’ gland (28 °Cd) and ‘Mihi’ Persian (25 °Cd) clovers. All species had a base temperature of 0 °C. ‘Mihi’ Persian clover had an optimum temperature (Topt) of 33 °C and a maximum temperature (Tmax) of 45 °C, while all the other species had Topt between 16–20 °C and Tmax of c. 34 °C. The maximum final germination percentage was above 60% for ‘Cefalu’ arrowleaf clover and 80% for the other three species.

Genome sequence of the clover-nodulating Rhizobium leguminosarum bv. trifolii strain SRDI943.

Rhizobium leguminosarum bv. trifolii SRDI943 (strain syn. V2-2) is an aerobic, motile, Gram-negative, non-spore-forming rod that was isolated from a root nodule of Trifolium michelianum Savi cv. Paradana that had been grown in soil collected from a mixed pasture in Victoria, Australia. This isolate was found to have a broad clover host range but was sub-optimal for nitrogen fixation with T. subterraneum (fixing 20-54% of reference inoculant strain WSM1325) and was found to be totally ineffective with the clover species T. polymorphum and T. pratense. Here we describe the features of R. leguminosarum bv. trifolii strain SRDI943, together with genome sequence information and annotation. The 7,412,387 bp high-quality-draft genome is arranged into 5 scaffolds of 5 contigs, contains 7,317 protein-coding genes and 89 RNA-only encoding genes, and is one of 100 rhizobial genomes sequenced as part of the DOE Joint Genome Institute 2010 Genomic Encyclopedia for Bacteria and Archaea-Root Nodule Bacteria (GEBA-RNB) project.

Nodule occupancy by Rhizobium leguminosarum strain WSM1325 following inoculation of four annual Trifolium species in Canterbury, New Zealand

The genotype of nodule occupants in four annual clovers – balansa (Trifolium michelianum), Persian (Trifolium resupinatum), gland (Trifolium glanduliferum) and arrowleaf (Trifolium vesiculosum) – was investigated. The clovers were inoculated with the ALOSCA® group C granule preparation of strain WSM1325. A total of 224 strains were recovered from root nodules with between 55 and 58 strains for each clover species. Genotyping showed that no strains had fingerprints identical to strain WSM1325. The nodule occupants were diverse with 26, 35, 31 and 32 genotypes identified on arrowleaf, balansa, gland and Persian clovers, respectively. Arrowleaf clover had some specificity for genotype A with 43% of nodules occupied by this strain. The most dominant strain for the other three clovers ranged between 13%–18% occupancy. This work demonstrates a high diversity of naturalized rhizobia strains in New Zealand soils that had the ability to nodulate these top flowering annual clover species.

Characterization and quantification of secondary metabolite profiles in leaves of red and white clover species by NIR and ATR-IR spectroscopy

Different varieties of two clover species (Trifolium pratense L. and Trifolium repens L.), cultivated in 2008 and 2009 were analysed by near-infrared (NIR) and mid-infrared (MIR) spectroscopy for establishing a fast and reliable quantification protocol for isoflavones and phenolic acids. Based on HPLC–UV/MS reference data, good results were obtained by PLS regression for the prediction of total isoflavone (R2=0.90) as well as for glycitin content (R2=0.88). Because of the lower concentration of formononetin and phenolic acids, their prediction quality was generally slightly lower (R2=0.73 and R2=0.64, respectively) compared to those of the isoflavones. The applicability of ‘leave one out’ cross validation for such a large data set is proven by comparison to an averaged randomized test-set validation leading to similar results. Additionally, the large sample set (n=624) was screened by hierarchical cluster analysis allowing a fast evaluation of influences resulting from different cultivation parameters on the isoflavone and phenolic acid content. Climatic changes (cultivation year, date of harvest) seem to have the most impact on the metabolic profile as indicated by higher variability in the referring spectra when both cultivation years were simultaneously regarded. This work offers a new vibrational spectroscopic approach for the qualitative and quantitative determination of isoflavone and phenolic acid profiles, directly performed in the plant material without any laborious sample preparation and time-consuming chromatography. Once validated by HPLC reference, MIR and NIR spectroscopy can be used for the reliable prediction of secondary metabolites in clover as well as for fast screening and pre-evaluation of the diversity of a large sample set, aiming to reduce analytical costs, chemical waste and expenditure of time.

Molecular characterization of five betacryptoviruses infecting four clover species and dill

The family Partitiviridae includes plant (Alphacryptovirus and Betacryptovirus), fungal (Partitivirus) and protozoan (Cryspovirus) viruses with bisegmented dsRNA genomes and isometric virions. Cryptic viruses commonly occur in different plant species without causing any symptoms. So far, numerous sequences have been determined for viruses of the genus Alphacryptovirus, but no sequence is available for any assigned member of the genus Betacryptovirus. Following extraction, cloning and sequence analysis of double-stranded RNA in this study, we report the molecular properties of three assigned members of the genus Betacryptovirus, white clover cryptic virus 2, red clover cryptic virus 2 and hop trefoil cryptic virus 2, and two new putative betacryptoviruses found in crimson clover and dill. Betacryptoviruses share sequence motifs with members of the genus Partitivirus. In phylogenetic analyses, members of the genus Betacryptovirus formed a new sub-cluster within the clusters containing members of the genus Partitivirus. Our results provide evidence for a distinct evolutionary lineage of dsRNA viruses of plants and fungi.

Differential Response of FourTrifoliumSpecies to Common Broadleaf Herbicides: Implications for Mixed Grass-Legume Swards

Clovers are commonly included as utility plants within mixed grass swards, such as pastures and roadside right-of-ways. As such, they provide supplemental nitrogen, quality forage, and insect habitat. Yet weed control within mixed swards is often hampered by the lack of selective herbicides that are tolerated by clovers. Differential tolerance of legumes to common row-crop and pasture herbicides has previously been reported, yet little information is available that is specific to clover species. Herbicide injury of clover is often inconsistent, hypothetically due to differential species tolerance. Field and greenhouse experiments were conducted with the objective of testing differential tolerance amongst four clover species. Our experiments suggest varying tolerances amongst clover species and common broadleaf herbicides. Only imazaquin control differed due to species; however, treatment by clover interactions were further demonstrated due to variable reductions in clover height. Imazaquin, 2,4-D, 2,4-DB, and triclopyr height reductions differed due to clover species. Differential clover response to herbicide treatment should be an important consideration when managing mixed grass–clover swards and should be accounted for in future research. On a more practical level, our experiments demonstrate a range of herbicides that effectively control clover species, including atrazine, dicamba, clopyralid, 2,4-D, triclopyr, metsulfuron, and trifloxysulfuron. However, results suggest that 2,4-DB, imazethapyr, and bentazon are candidate herbicides for weed control in scenarios in which clover is a desirable crop.

The occurrence of isoflavones in some domestic clover varieties

Preliminary investigations were carried out in order to ascertain the occurrence of isoflavonoid compounds characterized by estrogenic activity, in five domestic species of clover: <i>Trifolium pratense</i> L., <i>T. repens</i> L., <i>T. incarnatum</i> L., <i>T. resupinatum</i> L. and <i>T. hybridum</i> L. Large amounts of biochanin A (0.8% d.m.) and formononetin (0.7% d.m.) and small amounts of genistein were identified in the green parts of red clover. In the remaining species, small amounts of formononetin and genistein were found. In all the species of clover, free isoflavonoid aglycones and glycosides were found. Laboratory tests carried out on mice showed that only <i>T. pratense</i> contained high estrogen activity. Red clover also had an unidentified factor which inhibited the increase of the body weight of young mice.

The impact on grass vegetation of materials reducing gravel road dustiness

Materials used to reduce dustiness on gravel roads affect both the gravel road surfacing and the neighbouring vegetation. Materials used to reduce dustiness may access vegetation directly (when sprayed on gravel roads) and indirectly (when leached out by precipitation). The investigation examined a new substance, the aqueous solution Safecote (of different concentrations) and its mixtures with calcium chloride. 10%, 20% and 30% concentrations of Safecote and 36.5% of calcium chloride were used. The mixture ratio was 1:1 by volume. The investigation addressed the impact of the applied solutions on the length and viability of the above-ground part of plants. The timothy grass, white clover and crimson clover species of grass vegetation were selected for the investigation. The choice was determined by the fact that these species frequently grow in pastures by gravel roads. As it was determined during the investigation the viability of the selected plants in non-contaminated soil was 85-89%, in soil contaminated with dust reducing agent was 67-88% using solution Safecote, and 0-1% when applying mixtures of solutions. After 6 weeks of growth the length of above-ground part was 6.41-8.57 cm in uncontaminated soil, 4.22-8.18 cm in soil contaminated with Safecote solution and 0.00-2.07 cm in soil contaminated with the mixture.

Phytotoxic Effect, Uptake, and Transformation of Biochanin A in Selected Weed Species

Certain isoflavones are plant growth inhibitors, and biochanin A is a major isoflavone in clover species used for weed management. The effect of biochanin A on the monocot weed species Echinochloa crus-galli L. and Lolium perenne L. and dicot species Silene noctiflora L., Geranium molle L., and Amaranthus caudatus L. was evaluated in agar medium bioassays. S. noctiflora and G. molle root growth was progressively inhibited with increasing concentrations of biochanin A, whereas the monocot species were unaffected. With regard to the dicot species, S. noctiflora (EC(50) = 35.80 μM and EC(25) = 5.20 μM) was more susceptible than G. molle (EC(50), EC(25) > 400 μM). S. noctiflora, G. molle, and E. crus-galli root and shoot samples, representing a susceptible, a less susceptible, and a nonsusceptible species, respectively, were analyzed by LC-MS to quantify biochanin A and its transformation products. Biochanin A and its known transformation products genistein, dihydrobiochanin A, pratensein, and p-coumaric acid were quantified. Sissotrin was identified and quantified while assigning unknown peaks. The treated root samples contained more biochanin A, genistein, pratensein, and dihydrobiochanin A than shoot samples.

Identifying abnormalities in symbiotic development between Trifolium spp. and Rhizobium leguminosarum bv. trifolii leading to sub-optimal and ineffective nodule phenotypes.

Legumes overcome nitrogen limitations by entering into a mutualistic symbiosis with N(2)-fixing bacteria (rhizobia). Fully compatible associations (effective) between Trifolium spp. and Rhizobium leguminosarum bv. trifolii result from successful recognition of symbiotic partners in the rhizosphere, root hair infection and the formation of nodules where N(2)-fixing bacteroids reside. Poorly compatible associations can result in root nodule formation with minimal (sub-optimal) or no (ineffective) N(2)-fixation. Despite the abundance and persistence of strains in agricultural soils which are poorly compatible with the commercially grown clover species, little is known of how and why they fail symbiotically. The aims of this research were to determine the morphological aberrations occurring in sub-optimal and ineffective clover nodules and to determine whether reduced bacteroid numbers or reduced N(2)-fixing activity is the main cause for the Sub-optimal phenotype. Symbiotic effectiveness of four Trifolium hosts with each of four R. leguminosarum bv. trifolii strains was assessed by analysis of plant yields and nitrogen content; nodule yields, abundance, morphology and internal structure; and bacteroid cytology, quantity and activity. Effective nodules (Nodule Function 83-100 %) contained four developmental zones and N(2)-fixing bacteroids. In contrast, Sub-optimal nodules of the same age (Nodule Function 24-57 %) carried prematurely senescing bacteroids and a small bacteroid pool resulting in reduced shoot N. Ineffective-differentiated nodules carried bacteroids aborted at stage 2 or 3 in differentiation. In contrast, bacteroids were not observed in Ineffective-vegetative nodules despite the presence of bacteria within infection threads. Three major responses to N(2)-fixation incompatibility between Trifolium spp. and R. l. trifolii strains were found: failed bacterial endocytosis from infection threads into plant cortical cells, bacteroid differentiation aborted prematurely, and a reduced pool of functional bacteroids which underwent premature senescence. We discuss possible underlying genetic causes of these developmental abnormalities and consider impacts on N(2)-fixation of clovers.

Some chemical and morphological properties of five clover species (Trifolium sp.) at different aspect of pasture in Belovets village (Razgrad), Bulgaria

The aim of investigation was to determine the effects of aspect (north and south) on some morphological [plant height (cm), number of stems per plant, main stem diameter (mm), number of leaves per main stem, petiole length (cm), leaflet length (cm), leaflet width (cm), leaf: stem ratio] and chemical [crude protein (%), crude cellulose (%), calcium (%), phosphorus (%), potassium (%) and magnesium (%) ratios] properties of five clover species [hare’s-food clover (Trifolium arvense L.), field clover (T. campestre Schreb.), suckling clover (T. dubium Sibth.), alsike clover (T. hybridum L.) and zigzag clover (T. medium L.)] in pasture vegetation. The plant height, main stem diameter, number of leaves per main stem, petiole length, leaflet length, leaflet width, leaf: stem, crude protein, crude cellulose, calcium and potassium ratios were affected by aspect. The maximum plant height (65.53 cm), leaf: stem ratio (1.17) and crude protein ratio (20.00%) were found in zigzag clover on north-facing of pasture. The highest magnesium ratio (0.41%) and lowest number of stems per plant (4.85) were determined from the zigzag clover. The hare’s-food clover showed lower values (P<0.01) than the other clovers for phosphorus content (0.275%). The main stem diameter ranged from 3.53 to 5.27 mm. The north-facing of pasture had highest number of leaves per main stem (17.07) and petiole length (1.83 cm). The maximum leaflet length (3.50 cm) and width (2.55 cm) were measured for alsike clover on north-facing of pasture. The highest crude cellulose (28.23%) and calcium (3.13%) ratios were determined in hare’s-food clover on south-facing of pasture, whereas the lowest potassium ratio (2.37-2.39) was found in same clover species on each aspect of pasture.

Extracts from Trifolium pallidum and Trifolium scabrum aerial parts as modulators of blood platelet adhesion and aggregation

A growing number of reports indicate that some species of clover (Trifolium) may have remarkable medical importance; however, the effects of these plants on blood platelets and hemostasis are inadequately recognized. This work was designed to study the effects of Trifolium pallidum and Trifolium scabrum extracts on the functions of human blood platelets in vitro. Platelet suspensions were preincubated with extracts from aerial parts of T. pallidum (phenolic fraction and clovamide fraction) and T. scabrum (phenolic fraction) at the final concentrations of 12.5, 25, and 50 µg/ml. Then, for platelet activation thrombin (0.1 U/ml), thrombin receptor activating peptide (TRAP; 20 µM), or adenosine diphosphate (ADP; 1 µM) were used. The effects of Trifolium extracts on adhesion of blood platelets to fibrinogen and collagen were determined by enzyme-linked immunosorbent assay (ELISA) method. Platelet aggregation was monitored on a dual-channel Chronolog aggregometer. In these studies, we also compared the action of tested plant extracts with the effects of another antiplatelet plant-derived compound – resveratrol (3,4′,5-trihydroxystilbene). The performed assays demonstrated that the tested extracts might influence the platelet functions in vitro. The inhibitory, concentration-dependent effects of all tested extracts on adhesion of thrombin-stimulated platelets to collagen was found. Both extracts from T. pallidum and from T. scabrum reduced the thrombin-induced platelet adhesion to fibrinogen. Furthermore, in the presence of all three extracts, the platelet aggregation induced by thrombin was slightly inhibited. Our results also indicate that the tested plant extracts (at the highest concentrations used of 50 µg/ml), similar to purified resveratrol, inhibit selected steps of platelet activation stimulated by both proteolytic (thrombin) and nonproteolytic agonists (TRAP or ADP). In the comparative studies, T. pallidum and T. scabrum extracts was not found to be more effective antiaggregatory factor, than resveratrol. Extracts from T. pallidum and T. scabrum aerial parts reveal antiplatelet properties: the antiadhesive effect was similar to that of the reference compound resveratrol, whereas the antiaggregant effect was less marked. The results obtained suggest that these plants may be a promising source of natural compounds, valuable in the prevention of the enhanced activity of blood platelets in numerous cardiovascular diseases, observed in menopausal or postmenopausal women.

Comparative Genetic Mapping and Discovery of Linkage Disequilibrium Across Linkage Groups in White Clover (Trifolium repens L.).

White clover (Trifolium repens L.) is an allotetraploid species (2n = 4X = 32) that is widely distributed in temperate regions and cultivated as a forage legume. In this study, we developed expressed sequence tag (EST)–derived simple sequence repeat (SSR) markers, constructed linkage maps, and performed comparative mapping with other legume species. A total of 7982 ESTs that could be assembled into 5400 contigs and 2582 singletons were generated. Using the EST sequences that were obtained, 1973 primer pairs to amplify EST-derived SSR markers were designed and used for linkage analysis of 188 F1 progenies, which were generated by a cross between two Japanese plants, ‘273-7’ and ‘T17-349,’ with previously published SSR markers. An integrated linkage map was constructed by combining parental-specific maps, which consisted of 1743 SSR loci on 16 homeologous linkage groups with a total length of 2511 cM. The primer sequences of the developed EST-SSR markers and their map positions are available on http://clovergarden.jp/. Linkage disequilibrium (LD) was observed on 9 of 16 linkage groups of a parental-specific map. The genome structures were compared among white clover, red clover (T. pratense L.), Medicago truncatula, and Lotus japonicus. Macrosynteny was observed across the four legume species. Surprisingly, the comparative genome structure between white clover and M. truncatula had a higher degree of conservation than that of the two clover species.

Contributions of Overseeded Clovers to Bermudagrass Pastures in Several Environments

ABSTRACTBermudagrass [Cynodon dactylon (L.) Pers.], a base forage in southeastern United States livestock production, often fails to meet nutrient requirements of some classes of livestock. Contributions of arrowleaf (Trifolium vesiculosum Savi), ball (Trifolium nigrescens Viv.), berseem (Trifolium alexandrinum L.), crimson (Trifolium incarnatum L.), red (Trifolium pratense L.), and white (Trifolium repens L.) clovers to overseeded bermudagrass swards were compared with monoculture bermudagrass receiving 0, 112, or 225 kg ha−1 of N fertilizer on a range of sites. Berseem and crimson clovers produced up to 2.2 Mg ha−1 in March and early April, with berseem particularly reliable on fertile silt loam soils. Red clover was about 3 wk later with growth continuing until July most dependably at the more northern of the loam‐soil locations. Intermediate white clover, although not managed optimally for the species, was a productive late clover only at the southern location. All clovers overseeded on Darley fine sand were unsuccessful both years. Variable responses among clover species and sites from overseeded bermudagrass indicate that this clover production approach is very site specific in the lower southeastern United States.

Preliminary assessment of bladder clover (Trifolium spumosum L.) as an annual legume for ley farming systems in southern Australia

Trifolium spumosum L. (bladder clover) is an aerial seeding annual legume that is adapted to fine-textured soils throughout the Mediterranean Basin. This article is the first of two papers that describe the process of domestication of T. spumosum as a new species to commercial agriculture. This paper describes a broad range of investigations into the ecology, agronomy and rhizobiology of this new species. Through a series of five experiments, we have tested the general hypothesis that T. spumosum accessions demonstrate a range of sought-after agronomic traits and offer an alternative to annual Medicago spp. for ley farming systems in the medium to low rainfall areas of the mixed crop/livestock zone of southern Australia. T. spumosum presents seeds at the top of the canopy in heads that do not readily shatter, so seed can be harvested using conventional cereal harvesters instead of the specialist suction equipment required for harvest of seed from annual T. subterraneum and Medicago spp. T. spumosum was found to be relatively fecund and had high levels of biomass production in comparison to the other annual legumes that were tested. The species also demonstrated high levels of within-season hardseededness (remaining hard in summer and softening in autumn) so seedbanks would be protected from summer rainfall events. In addition, T. spumosum showed high levels of between-season dormancy, which allows the species to carry a seedbank through a cropping phase or series of poor seasons. A herbicide experiment showed that clover species varied in tolerances, with T. spumosum the least sensitive of all of the legumes tested to Flumetsulam. A cross-inoculation experiment to measure symbiotic effectiveness revealed that WSM1325 (current clover strain) surpasses WSM409 (previous strain) in its relationship with the annual clovers of contemporary interest, while being highly effective at nitrogen fixation with T. spumosum. The results of this study and an associated investigation into feeding value indicate that T. spumosum offers a productive alternative to annual Medicago spp. on fine-textured soils. Of the T. spumosum accessions tested, the most promising has been released under the cultivar name of AGWEST Bartolo.