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Summary: Melilotus species are used as green manure and rotation crops worldwide and contain abundant pharmacologically active coumarins. However, there is a paucity of information on its genome and coumarin production and function. Here, we reported a chromosome‐scale assembly of Melilotus albus genome with 1.04 Gb in eight chromosomes, containing 71.42% repetitive elements. Long terminal repeat retrotransposon bursts coincided with declining of population sizes during the Quaternary glaciation. Resequencing of 94 accessions enabled insights into genetic diversity, population structure, and introgression. Melilotus officinalis had relatively larger genetic diversity than that of M. albus. The introgression existed between M. officinalis group and M. albus group, and gene flows was from M. albus to M. officinalis. Selection sweep analysis identified candidate genes associated with flower colour and coumarin biosynthesis. Combining genomics, BSA, transcriptomics, metabolomics, and biochemistry, we identified a β‐glucosidase (BGLU) gene cluster contributing to coumarin biosynthesis. MaBGLU1 function was verified by overexpression in M. albus, heterologous expression in Escherichia coli, and substrate feeding, revealing its role in scopoletin (coumarin derivative) production and showing that nonsynonymous variation drives BGLU enzyme activity divergence in Melilotus. Our work will accelerate the understanding of biologically active coumarins and their biosynthetic pathways, and contribute to genomics‐enabled Melilotus breeding. [ABSTRACT FROM AUTHOR]

Melilotus albus Medik. is a legume species with potential to be used as a forage or conserved fodder in Northwest China. Breeding M. albus as a forage crop is focused on simultaneously improving forage yield and reducing coumarin (Cou) content. The goal of the present study was to estimate genotypic variation for several key agronomic traits and to evaluate the impact of single-trait selection and Smith--Hazel-index-based multitrait selection for herbage dry weight (DW), plant height (PH), stem number (SN), and leaf area (LA). A quantitative genetic analysis was conducted on trait measurements from 25 half-sib (HS) families evaluated at Yuzhong and Linze, in China. Significant (P < 0.05) genotypic variation among the HS families for all traits was observed. There was also significant (P < 0.05) genotype x environment interaction for all traits except for LA. The predicted genetic gain, based on estimated genotypic variance, for single-trait selection varied from 2.3 to 30.3% per selection cycle. Pattern analysis of the HS family ´ multitrait best linear unbiased prediction matrix provided a graphical summary of the association among the traits, as well as the four HS family groups generated from clustering. Some members within Group 1 could be crossed to generate a breeding population to be used in recurrent selection for M. albus cultivar development in Northwest China. The applicability of a Smith--Hazel selection index to increase expression of the traits DW, PH, and SN and reduce LA, indirectly reducing Cou content, was confirmed. This index enabled identification of families for increasing key biomass traits and decreasing Cou production. [ABSTRACT FROM AUTHOR]

• Aerenchymatous phellem (secondary aerenchyma) has rarely been studied in roots. Its formation and role in internal aeration were evaluated for Melilotus siculus, an annual legume of wet saline land. • Plants were grown for 21 d in aerated or stagnant (deoxygenated) agar solutions. Root porosity and maximum diameters were measured after 0, 7, 14 and 21 d of treatment. Phellem anatomy was studied and oxygen (O2) transport properties examined using methylene blue dye and root-sleeving O2 electrodes. • Interconnecting aerenchymatous phellem developed in hypocotyl, tap root and older laterals (but not in aerial shoots), with radial intercellular connections to steles. Porosity of main roots containing phellem was c. 25%; cross-sectional areas of this phellem were threefold greater for stagnant than for aerated treatments. Root radial O2 loss was significantly reduced by complete hypocotyl submergence; values approached zero after disruption of hypocotyl phellem below the waterline or, after shoot excision, by covering hypocotyl phellem in nontoxic cream. • Aerenchymatous phellem enables hypocotyl-to-root O2 transport in M. siculus. Phellem increases radially under stagnant conditions, and will contribute to waterlogging tolerance by enhancing root aeration. It seems likely that with hypocotyl submerged, O2 will diffuse via surface gas-films and internally from the shoot system. [ABSTRACT FROM AUTHOR]

The article focuses on the registration of N30-N56, N741, N743, N745, N747, U362, U363, U367, U369-U374, U389.U394, U396-U398, and U500 sweetclover genetic stocks. Forty-nine white-flowered sweetclover (Melilotus alba Medik.) genetic stocks, a yellow-flowered sweetclover genetic stock, were developed jointly by the U.S. Department of Agriculture-Agricultural Research Service and the Agricultural Research Division, Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln, Nebraska and were jointly released in May 2004. The genetic stocks, which contain unique combinations of genes and traits, were developed over more than three decades of cooperative sweet- clover genetic research. The development of 16 lines involved both annual and biennial forms of M. alba, and the greenhouse conditions under which seed of these lines were produced did not permit distinguishing between these forms. U389 is an annual line that was derived from a single plant of the introduction, P1165554, mentioned above. All of the other U-numbered lines were developed following treatment of U389 seed with ethyl methanesulfonate. Seed should be scarified before planting. It is requested that appropriate recognition be made if these genetic stocks contribute to research or the development of a new breeding line or cultivar.

Many recent studies suggest that more diverse communities are more resistant to invasion. Community characteristics that most strongly influence invasion are uncertain, however, due to covariation of diversity with competition and crowding. We examined separately the effects of species richness and dominance on invasion by an exotic legume, Melilotus officinalis, in intact, native Kansas grassland. We manipulated dominance of C4 grasses by reducing their abundance (i.e. ramet densities) by ∼25 and 50%. In addition, richness was reduced by removing species that were mainly rare and uncommon as might be expected with environmental changes such as drought and fragmentation. In both years of the study (2001–2002), invasibility, measured as peak establishment of Melilotus, was not affected by a 3-fold reduction in species richness, nor was there an interaction between loss of species and reduced dominance on invasion. In contrast, reductions in abundance of the dominants significantly reduced invasibility of the grassland plots in both years. Because the abundance of dominants was highly correlated with measures of competition (i.e. ratio of dominant biomass to total biomass) and crowding (total stem densities), this pattern was opposite to that expected if competition were indeed limiting invasion. Rather, invasion appeared to be facilitated by the dominant species, most likely because reduced dominance increased environmental stress. Our results suggest that dominance is the key community characteristic determining invasibility, because highly competitive and space-filling species can either enhance or reduce susceptibility to invasion depending on whether dominants create a more competitive environment or alleviate stressful conditions. [ABSTRACT FROM AUTHOR]

Invasion of nitrogen-fixing non-native plant species may alter soil resources and impact native plant communities. Altered soils may be the driving mechanism that provides a suitable environment to facilitate future invasions and decrease native biodiversity. We hypothesized that Melilotus invasion would increase nitrogen availability and produce soil microclimate and biochemical changes, which could in turn alter plant species composition in a montane grassland community. Our research addressed the effects of white and yellow sweet clover ( Melilotus officinalis and M. alba) invasion on soil characteristics and nitrogen processes in the montane grasslands in Rocky Mountain National Park. We sampled soil in replicate sites of Melilotus-invaded and control (non-invaded) patches within disturbed areas in montane grassland habitats. Soil composites were analysed for available nitrogen, net nitrogen mineralization, moisture, carbon/nitrogen (C : N ratio), texture, organic matter and pH. Data were recorded at three sample dates during the growing seasons of 1998 and 1999. Contrary to our expectations, we observed lower nitrogen availability and mineralization in invaded patches, and differences in soil moisture content and soil C : N. Soil C : N ratios were higher in invaded plots, in spite of the fact that Melilotus had the lowest C : N ratios of other plant tissue analysed in this study. These findings provide land managers of natural areas with a better perspective on the possibilities of nitrogen-fixing species impact on soil nutrient levels. [ABSTRACT FROM AUTHOR]

The allocation of biomass and mineral elements Na, K, Ca, P, N, Fe, Cu, Mn and Zn) during the ontogenetic cycle of annual sweetclover (Melilotus segetalis (Brot.) Ser.) growing under favourable and saline conditions has been studied. Plants were grown in a glasshouse, in pots with siliceous substrate- and watered with Hoagland solution. Half were salinized by adding 170 mol m-3 NaCl (15 dS m-1 to the solution. Eleven harvests at 15 d intervals measured the dry weight distribution within the plant and the mineral composition. Allocation relative to biomass (ARB) in each plant organ, both under favourable and salt-stress conditions, was calculated For each mineral element. Biomass and mineral elements were allocated independently within M. segetalis and the general pattern changed with age and was affected by salinity. Salt-stressed plants were smaller and invested proportionately more biomass in leaves. Na was accumulated in roots of young plants and excluded from leaves and fruits, whereas K was depleted from roots and accumulated in leaves and fruits. immobile Ca accumulated in leaves; with age. Phloem-mobile P and N were translocated to flowers and fruits. Fe, Cu and Zn were diluted in leaves and not affected by salt, whereas Mn concentration increased with age and salinity. The switch to reproduction and increased demand fur nutrients induced drastic changes in the allocation pattern of mineral elements. Salinity induced a re-allocation of biomass and mineral elements in all plant organs except the reproductive structures, as part of a whole-plant response to minimize salt toxic effects, to achieve osmotic adjustment, to present the reproductive output, and to compensate nutrient imbalance. [ABSTRACT FROM AUTHOR]

The aim of this work was to examine variation for activity of symbiosis with Rhizobium meliloti in alfalfa, sweet clover and fenugreek. Seed specimens were obtained from the collection of the All-Union Research Institute for Plant Breeding and Rhizobium strains from the All-Union Research Institute for Agricultural Microbiology, both in Leningrad. Sterile methods of vegetative culture were employed. Statistical analysis of data on inter- and intracultivar variation allow one to suppose that in alfalfa and sweet clover, nitrogenase activity and symbiotic efficiency (ability of plants to increase biomass after inoculation) are controlled by different groups of genes. The latter symbiotic property is more strictly controlled by host genotype than the former. Fenugreek appeared to be more variable in its capacity for symbiosis than alfalfa and sweet clover. Differences between genotypes in symbiotic activity correlate with division into subspecies and are inherited in self-fertile progeny of fenugreek plants. Differences between R. meliloti strains for the efficiency of symbiosis with heterogenic natural fenugreek population are expressed to a lesser degree than with plants of more homogenic cultivar populations. [ABSTRACT FROM AUTHOR]

The cytoskeleton of columella cells is believed to be involved in maintaining the developmental polarity of cells observed as a reproducible positioning of cellular organelles. It is also implicated in the transduction of gravitropic signals. Roots of sweet clover (Melilotus alba L.) seedlings were treated with a microfilament disrupter, cytochalasin D, on a slowly rotating horizontal clinostat (2 rpm). Electron micrographs of treated columella cells revealed several ultrastructural effects including repositioning of the nucleus and the amyloplasts and the formation of endoplasmic reticulum (ER) whorls. However, experiments performed during fast clinorotation (55 rpm) showed an accumulation (but no whorling) of a disorganized ER network at the proximal and distal pole and a random distribution of the amyloplasts. Therefore, formation of whorls depends upon the speed of clinorotation, and the overall impact of cytochalasin D suggests the necessity of microfilaments in organelle positioning. Interestingly, a similar drug treatment performed in microgravity aboard the US Space Shuttle Endeavour (STS‐54, January 1993) caused a displacement of ER membranes and amyloplasts away from the distal plasma membrane. In the present study, we discuss the role of microfilaments in maintaining columella cell polarity and the utility of clinostats to simulate microgravity. [ABSTRACT FROM AUTHOR]

Specific absorption rates (SAR) and specific utilization rates (SUR) of sodium, chloride, potassium, calcium, magnesium and phosphate ions were determined for Melilotus segetalis (Brot.) Ser. (annual sweetclover) grown under both control and salinized conditions (NaCI treatment of CE =15 dS m-1) for a complete life cycle with sequential harvests. The behaviour over time of the SARs and SURs of the mineral elements was in general correlated with relative growth rate (RGR) kinetics, with a parabolic trend during the vegetative phase and a progressive linear decrease during the reproductive stage. Salinity significantly reduced the SARs of K and Mg but did not affect the SARs of Ca and P during the vegeta- five phase. During the reproductive stage, however, the SARs of K, Ca and P of salt-stressed plants were higher than in control plants. The similar SARs of total cations (TC) found in control and salt-stressed plants may indicate compensatory mechanisms to maintain a constant total cation content. Salt-stressed plants showed lower SURs of K, Ca and P during the vegetative phase, and lower SURs of K and P but a higher SUR of Mg during the reproductive stage. A nutrient imbalance, caused by a lower root efficiency in absorbing K and Mg and a lower leaf efficiency in producing biomass per unit of K, Ca and P, apparently con- tributed to the salt-induced reduction in growth during the vegetative phase of M. segetalis. The switch to non- reduced, compensated growth during the reproductive phase may have been caused by a higher nutrient demand which increased the root efficiency in absorbing K, Ca and P and the leaf efficiency in utilizing Mg. [ABSTRACT FROM AUTHOR]

Annual sweetclover plants [Melilotus segetalis (Brot.) Ser.] were grown for a complete life cycle with and without saline (NaCl treatment of CE=15 dS m-1). Growth and partitioning analyses were performed. Sequential harvests (every 15 d) during the life cycle, and separation of plant material into roots, stems, petioles, leaves and reproductive structures were carried out Salt treatment reduced growth during the early and middle stages of the life of the plant, but did not significantly affect RGR in the reproductive phase. The root-shoot allometric coefficient of salinized plants in the generative phase decreased more than in control plants. We suggest that salinity-induced growth reduction in M. segetalis was primarily a result of a lower unit leaf rate (ULR) despite an increased leaf area ratio (LAR). Earlier flowering, higher biomass allocation to shoot and greater reproductive investment, but similar relative growth rate (RGR), were some of the main characteristics of salt-stressed plants compared to controls during the reproductive phase, these apparently being associated with increased sink strength caused by developing flowers and fruits. [ABSTRACT FROM AUTHOR]

The acidic and calcareous populations of Melilotus alba behave differently when grown in competition than when grown in isolation from each other. Thus, the acidic population which did well in both calcareous and acidic media in competition-free cultures, showed good growth yield in acidic soils only when in competition with the calcareous population. Further, the differences observed between the two populations in competition-free experiments became more pronounced when grown mixed. The time of introduction of either of the two populations into the mixture affects the final dry weight yield of the shoot, depending upon the soil type. In mixed cultures of the two populations, the calcareous population grown in an acidic soil and the acidic population grown in a calcareous soil responded by mortality of individuals, especially when the second population in each case was introduced earlier into the mixture. [ABSTRACT FROM AUTHOR]

The article focuses on observations on the latest of the Middlesex, England series of chalk pits. The floor area was dominated by Melilotus officinalis in July 1933. The fluctuations may be due to the biennial habit and by 1942, it was hard to find plants in the pit. Melilotus flourishes on cliffs which are constantly eroded. Lotus corniculatus was not seen to be attacked by rabbits and it exploits crevices below the upper weathered chalk. The Medicago lupulina is a rapid colonizer of bare chalk but is susceptible to drought. Plants colonizing the Home Ground range include Achillea millefolium, Agrostis stolonifera and Plantago media.

We describe specific primers that amplify nine microsatellite DNA loci from Melilotus alba and Melilotus officinalis, both invasive plant species (Fabaceae) throughout North America. Allelic diversity was slightly lower for M. alba than for M. officinalis, as was expected heterozygosity. For both species, heterozygote deficit was observed at several loci. Genotypic diversity was very high for both species; the 29 plant samples of each species all had different multilocus genotypes. These markers will be used to determine the origins of the sweetclover invasion in Alaska and to compare patterns of diversity between subarctic and lower latitude populations. [ABSTRACT FROM AUTHOR]

What is known and objective: We report a case of severe liver dysfunction exacerbated after interferon beta (IFNB)-1b injection in a patient with multiple sclerosis (MS) who had been taking a melilot (sweet clover) supplement. Although IFNB-1b therapy for MS can cause mild liver dysfunction, severe hepatotoxicity attributable to supplement use has been reported. Case summary: A 23-year-old Japanese woman taking a melilot supplement containing coumarin at 10 mg/day for 3 years was admitted to our hospital to receive IFNB-1b therapy for MS. Fourteen days after subcutaneous injection of IFNB-1b every other day, her aspartate transaminase (AST) and alanine aminotransferase (ALT) levels were elevated at 235 and 681 IU/L, respectively. After the discontinuation of IFNB-1b therapy and supplement intake, AST and ALT returned to normal levels. Later, she started receiving an intramuscular injection of IFNB-1a weekly without supplement intake. She was able to continue IFNB-1a therapy this time, showing a slight elevation of AST level at 61 IU/L. What is new and conclusion: The combination of IFNB-1b therapy and melilot supplement intake may cause severe liver dysfunction in patients with MS. Given the doubtful value of the supplement, we suggest that it should be avoided by patients receiving interferon therapy. [ABSTRACT FROM AUTHOR]