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]

Understanding how a warmer and more variable climate will affect the productivity and stability of perennial forages in the establishment year is essential for determining forage management strategies resilient to the changing climate. We conducted an experiment from 2020–2021 and repeated it in 2021–2022 to determine how warmer and more variable temperatures affect yield of an alfalfa (Medicago sativa L.)–orchardgrass (Dactylis glomerata L.) mixture, as well as on the abundance of a winter annual weed, chickweed (Stellaria media), during the establishment year. We utilized open‐top chambers (OTCs) to manipulate air temperature in situ to impose three treatments: (1) constant warming (OTC present year‐round), (2) fluctuating warming (OTC present year‐round but temporarily removed prior to abrupt cold snaps), and (3) control (no OTC, ambient air temperature). OTCs increased air temperature within the alfalfa–orchardgrass canopy by an average of 0.45 and 0.72°C in Year 1 and Year 2, respectively; however, the effects of OTCs on air temperature varied temporally within and between years. Constant warming decreased alfalfa frost injury compared with the control, while the control and fluctuating warming resulted in similar levels of frost injury. Warmer temperature within the OTCs neither affected chickweed biomass nor the biomass of all other weed species. Both constant and fluctuating warming increased forage dry matter yield at the first harvest timepoint in the spring of both years, the period when preceding ambient air temperature tended to be cooler than other harvest timepoints. We found that the constant warming increased total forage yield (summed over the entire year) in Year 1, when precipitation was well above the 30‐year normal for our region, but decreased total forage yield in Year 2, when summer precipitation was substantially below the 30‐year normal. As global temperature continues to rise, yield loss of cool‐season perennial forages, such as alfalfa and orchardgrass, may be exacerbated in years without adequate precipitation. Therefore, exploring heat‐ and drought‐tolerant alternative forages, as well as management strategies that improve resilience to weather variability, will be increasingly important. [ABSTRACT FROM AUTHOR]

Background: Soil and water salinity are increasing problems worldwide, causing significantly reduced crop yields. Alfalfa (Medicago sativa L.) is often listed as salt‐sensitive, but field testing of improved cultivars is limited. Forage systems and improved high‐quality alfalfa varieties are needed to enable crop production under high salinity (HS) conditions. Methods: The objective of this study was to measure the yield and quality response of alfalfa to high saline conditions in the field and to document the relative saline tolerance of its varieties. HS irrigation water (electrical conductivity of water, or ECw 8.0–11.0 dS m−1) was applied to 33 nondormant alfalfa cultivars and were compared with low salinity (LS) treatments (ECw 0.5–1.2 dS m−1) over 4 years in a Mediterranean environment on a clay loam soil utilizing a split‐plot design. Crops were harvested seven to eight times per year, and the forage quality was measured on selected harvests utilizing near‐infrared spectroscopy. Results: The average yield loss due to HS treatment was 23.9% compared with LS treatment, but yields averaged 23.4 Mg ha−1 under HS over the 3 full years of production. This level of production is considered to be economically viable in this region. Differences in salinity tolerance between lines were identified in the field; individual cultivars lost 5%–35% of their LS yield when grown under HS conditions. Forage quality was significantly improved under HS versus LS conditions, but improvements were negatively correlated with biomass yield (R2 > 0.81), similar to responses observed in drought‐stressed alfalfa. Conclusions: These yield results confirm greenhouse studies, indicating that alfalfa is highly salt tolerant once established in the field, with potential for further improvement with tolerant cultivars. Salinity tolerance should be chosen based on total biomass yield as well as on the salinity tolerance index (HS yield relative to LS yield). Agronomic practices to mitigate salinity and sodicity are critical, along with improved cultivars. [ABSTRACT FROM AUTHOR]

Popillia japonica is a quarantine pest of priority interest for the EU, given its potentially important economic, social and environmental impacts. Alternative strategies to chemical methods are essential to limit its spread in newly infested areas with favourable climatic and environmental conditions. Saponins are biologically active molecules widely distributed in plants, displaying a well‐known repellent activity combined with a mortality effect against insects. In this context, saponins were extracted from alfalfa Medicago sativa, where medicagenic and zanhic acid glycosides and Soyasaponin I were the most abundant compounds and used in the laboratory and semi‐field experiments for treating leaves of susceptible host plants for P. japonica. Under laboratory conditions, a food deterrence effect and a significant mortality rate were observed using Corylus avellana leaves treated at increasing saponin concentrations, ranging from 1% to 5% w/v. Semi‐field condition experiment supported the food deterrence effect, as a significant food preference was observed for untreated plants of Vitis vinifera compared to treated plants. The promising results obtained suggest that alfalfa saponins could represent a potential eco‐friendly approach for Japanese beetle control. [ABSTRACT FROM AUTHOR]

Summary: Plant disease occurs simultaneously with insect attack. Arbuscular mycorrhizal fungi (AMF) modify plant biotic stress response. Arbuscular mycorrhizal fungi and pathogens may modify plant volatile organic compound (VOC) production and insect behavior. Nevertheless, such effects are rarely studied, particularly for mesocosms where component organisms interact with each other.Plant‐mediated effects of leaf pathogen (Phoma medicaginis) infection on aphid (Acyrthosiphon pisum) infestation, and role of AMF (Rhizophagus intraradices) in modifying these interactions were elucidated in a glasshouse experiment. We evaluated alfalfa disease occurrence, photosynthesis, phytohormones, trypsin inhibitor (TI) and total phenol response to pathogen and aphid attack, with or without AMF, and aphid behavior towards VOCs from AMF inoculated and non‐mycorrhizal alfalfa, with or without pathogen infection.AM fungus enhanced alfalfa resistance to pathogen and aphid infestation. Plant biomass, root : shoot ratio, net photosynthetic rate, transpiration rate, stomatal conductance, salicylic acid, and TI were significantly increased in AM‐inoculated alfalfa. Arbuscular mycorrhizal fungi and pathogen significantly changed alfalfa VOCs. Aphids preferred VOCs of AM‐inoculated and nonpathogen‐infected to nonmycorrhizal and pathogen‐infected alfalfa.We propose that AMF alter plant response to multiple biotic stresses in ways both beneficial and harmful to the plant host, providing a basis for strategies to manage pathogens and herbivore pests. [ABSTRACT FROM AUTHOR]

Under warmer and drier future conditions, global livestock and dairy production are threatened by impacts on the productivity and nutritional quality of pastures. However, morphological and nutritional adjustments within plants in response to warming and drought vary among species and less is known how these relate to production and forage quality. To investigate this, we grew two common pasture species, tall fescue (Festuca arundinacea: grass) and lucerne (Medicago sativa: legume), in a climate‐controlled facility, under different temperatures (ambient and elevated) and watering regimes (well‐watered and droughted). We found that drought had a strong negative impact on biomass production, morphology and nutritional quality while warming only significantly affected both species when response metrics were considered in concert, although to a lesser degree than the drought. Furthermore, interactions between warming and drought were only seen for lucerne, with a reduction in biomass and an increase in dead material and dry matter. In tall fescue, drought had bigger impacts on nutritional composition than morphological traits, while in lucerne, drought affected all morphological traits and most of the nutritional parameters. These findings suggest that in future climate scenarios, drought may be a stronger driver of changes in the morphology and nutritional composition of pasture grasses and legumes, compared to modest levels of warming. [ABSTRACT FROM AUTHOR]

This work focuses on the investigation of forage crops hybrid fescue and legume alfalfa response to drought at different levels of nitrogen fertilization. Plants were grown in pots filled with a mixture of field soil, perlite and fine sand with three (N0, N60 and N90 kg/ha) levels of nitrogen fertilization in a greenhouse. Drought stress was applied by withholding watering for 1 week, after which plants were left for a recovery period of 1 week. In most cases, the morphological indices of alfalfa did not differ significantly between the treatments. In contrast, the above-ground biomass of fescue grown under well-watered conditions was largely enhanced by N addition. The main trend of JIP test parameters was that nitrogen fertilizer did not have a significant effect on alfalfa. Contrarily, additional nitrogen content increased energy fluxes (such as absorption, trapping, electron transport, reduction of end acceptors) and density of reaction centres not only in well-watered but also in drought-affected fescue plants. An increase in nitrogen fertilizers increased content of pigments and flavonoids in fescue leaves. In conclusion, the stress tolerance index of hybrid fescue increased along with the increase in N content due to more efficient use of light energy and increased antioxidative capacity, all of which led to significantly higher production of above-ground biomass at higher N levels and drought stress. [ABSTRACT FROM AUTHOR]

Bees used alfalfa leaves but ignored alfalfa petals and cut marigold petals but not marigold leaves. Relative to the abundance of plants in cages, bees used alfalfa leaves, marigold petals, and mallow leaves 4.8, 8.9, and 6.1 times more than expected, respectively, but used mallow petals 1.9 times less than expected (Fig. Keywords: alfalfa leafcutting bee; behavior; Medicago sativa; Megachile rotundata; Megachilidae; reproduction EN alfalfa leafcutting bee behavior Medicago sativa Megachile rotundata Megachilidae reproduction 1 4 4 02/03/22 20220201 NES 220201 The alfalfa leafcutter bee ( I Megachile rotundata i , hereafter simply "leafcutter bee") is a solitary, cavity-nesting bee native to Eurasia, managed as an agricultural pollinator of alfalfa and several other crops in North America since the 1940s (Pitts-Singer and Cane 2011). Here, we describe the petal provisioning behavior and provide the first, to our knowledge, quantitative assessment of behavior related to leafcutter bee nest building material selection involving petals in a controlled environment. [Extracted from the article]

Breeding plants with polyploid genomes is challenging because functional redundancy hampers the identification of loss‐of‐function mutants. Medicago sativa is tetraploid and obligate outcrossing, which together with inbreeding depression complicates traditional breeding approaches in obtaining plants with a stable growth habit. Inducing dominant mutations would provide an alternative strategy to introduce domestication traits in plants with high gene redundancy. Here we describe two complementary strategies to induce dominant mutations in the M. sativa genome and how they can be relevant in the control of flowering time. First, we outline a genome‐engineering strategy that harnesses the use of microProteins as developmental regulators. MicroProteins are small proteins that appeared during genome evolution from genes encoding larger proteins. Genome‐engineering allows us to retrace evolution and create microProtein‐coding genes de novo. Second, we provide an inventory of genes regulated by microRNAs that control plant development. Making respective gene transcripts microRNA‐resistant by inducing point mutations can uncouple microRNA regulation. Finally, we investigated the recently published genomes of M. sativa and provide an inventory of breeding targets, some of which, when mutated, are likely to result in dominant traits. [ABSTRACT FROM AUTHOR]

For 10,000 years humans have altered plant traits through domestication and ongoing crop improvement, shaping plant form and function in agroecosystems. To date, studies have focused on how these processes shape whole‐plant or average traits; however, plants also have characteristic levels of trait variability among their repeated parts, which can be heritable and mediate critical ecological interactions. Here, we examine an underappreciated scale of trait variation—among leaves, within plants—that may have changed through the process of domestication and improvement. Variability at this scale may itself be a target of selection, or be shaped as a by‐product of the domestication process. We explore how levels of among‐leaf trait variability differ between cultivars and wild relatives of alfalfa (Medicago sativa), a key forage crop with a 7,000‐year domestication history. We grew individual plants from 30 wild populations and 30 cultivars, and quantified variability in a broad suite of physical, nutritive, and chemical leaf traits, including measures of chemical dissimilarity (beta diversity) among leaves within each plant. We find that trait variability has changed over the course of domestication, with effects often larger than changes in trait means. Domestic alfalfa had elevated among‐leaf variability in SLA, trichomes, and C:N; increased diversity in defensive compounds; and reduced variability in phytochemical composition. We also elucidate fundamental relationships between trait means and variability, and between overall production of secondary metabolites and patterns of chemical diversity. We conclude that within‐plant variability is an overlooked dimension of trait diversity in a globally critical agricultural crop. Trait variability is actually higher in cultivated plants compared to wild progenitors for multiple nutritive, physical, and chemical traits, highlighting a scale of variation that may mitigate loss of trait diversity at other scales in alfalfa agroecosystems, and in other crops with similar histories of domestication and improvement. [ABSTRACT FROM AUTHOR]

Unlike many crop seeds which are large in size, forage seeds are relatively small. Moreover, some forage seeds from the same genus, or even different genera, share similar morphologies in terms of colour, size, weight and so on. Alfalfa (Medicago sativa L.) and burr medic (Medicago polymorpha L.) also share similar morphology. However, alfalfa is a perennial, cross‐pollinated herbaceous species, whereas burr medic is considered an annual, self‐pollinating plant. Therefore, a universal and rapid method of discriminating burr medic seeds from alfalfa seeds or other similar forage seeds from different plant species is needed. Previous methods of discriminating similar‐looking forage seeds have been shown to be unreliable or time consuming. Here, a universal method that combines polymerase chain reaction (PCR) and polyacrylamide gel electrophoresis techniques was developed to discriminate alfalfa and burr medic. Based on the differences in the lengths of homologous genes caused by insertions and deletions between two species, a pair of primers was designed to discriminate the accessions of 15 alfalfa and 9 burr medic via visualizing the clearly different PCR amplicon sizes. In addition, the melting curve analysis was performed to investigate the specificity and reliability of the primer pair. The results showed two different melting peaks between the two species, further demonstrating this method can accurately and sensitively identify the two species. Thus, we believe that this method has the great potential to be extensively applied for the identification of contaminated seeds and breeding of forages. [ABSTRACT FROM AUTHOR]

Introduction: Medicago sativa contains flavonoids, saponins, coumarins, sterols, monoterpenes, and organic acids, with flavonoids being the main active constituents. Flavonoids naturally contain a 2‐phenylchromone structure with antioxidant, free radical scavenging, cardiovascular, and trace estrogen‐like effects. Objective: Screening and isolation of neuraminidase, lipoxidase, and lactate dehydrogenase inhibitors from M. sativa via ultrafiltration‐liquid chromatography‐mass spectrometry (UF‐LC–MS) combined with stepwise flow rate counter‐current chromatography (CCC). Method: Utilising the medicinal plants M. sativa as the research objects and UF‐LC–MS was used for activity screening followed by isolation and purification of the inhibitors by stepwise flow rate CCC. Finally, identification of the three active compounds was achieved by MS and nuclear magnetic resonance. Results: Three major compounds, viz. quercetin, genistein, and formononetin, were identified as potent neuraminidase, lipoxidase, and lactate dehydrogenase inhibitors, respectively. A two‐phase solvent system of ethyl acetate/methanol/n‐butanol/water (5.0:1.5:5.0:10; v/v/v/v) was subsequently selected for separation by stepwise flow rate CCC. Conclusion: This novel approach based on UF‐LC–MS and stepwise flow rate CCC represents a powerful tool for the screening and isolation of neuraminidase, lipoxidase, and lactate dehydrogenase inhibitors from complex matrices. Therefore, a useful platform for the large‐scale production of bioactive and nutraceutical ingredients was developed herein. An efficient method for the rapid screening and purification of potential NA, LDH, and LOX inhibitors from the M. sativa was established using UF‐LC‐MS combined with stepwise flow rate CCC.Three flavonoid compounds were successfully separated and their structures determined by MS and nuclear magnetic resonance (NMR).To the best of our knowledge, this is the first report of this technique for the screening and isolation of flavonoids from M. sativa [ABSTRACT FROM AUTHOR]

Legumes are used in crop rotations by both large‐scale and smallholder farmers alike to increase soil fertility, especially before high‐nitrogen‐demanding crops such as corn (maize). Legume crop residues and green manures are rich in nitrogen due to mutualistic rhizobia, bacteria that live in their roots and convert atmospheric nitrogen into a biologically available form. Growers can obtain recommendations from local extension offices about how much less inorganic nitrogen fertilizer needs to be added to a subsequent crop following different legume break crops for the predominant soil type (the nitrogen fertilizer replacement value, or NFRV). Due to the intimate relationship between legumes and rhizobia, conditions that affect plant health can also affect the rhizobia and how much nitrogen they provide. We use a combination of empirical data and previously published values to estimate reductions in nitrogen inputs under outbreaks of plant viruses of varying severity. We also use historical fertilizer prices to examine the economic impacts of this lost fertilizer for farmers. We find that fertilizer losses are greatest for crops that fix large amounts of nitrogen, such as clover and alfalfa as opposed to common bean. The economic impact on farmers is controlled by the proportion of plants with viral infections and the price of synthetic fertilizer. In a year of high disease prevalence, attention is normally focused on the yield of the diseased crops. We suggest that farmers growing legumes as break crops should be concerned about yields of subsequent crops as well. Viral diseases can be difficult to diagnose in the field, so the easiest way for farmers to prevent unexpected yield losses in subsequent crops is to test their soil when it is feasible to do so. [ABSTRACT FROM AUTHOR]

Summary: Alfalfa (Medicago sativa L.) is one of the most important forage crops throughout the world. Maximizing leaf retention during the haymaking process is critical for achieving superior hay quality and maintaining biomass yield. Leaf abscission process affects leaf retention. Previous studies have largely focused on the molecular mechanisms of floral organ, pedicel and seed abscission but scarcely touched on leaf and petiole abscission. This study focuses on leaf and petiole abscission in the model legume Medicago truncatula and its closely related commercial species alfalfa. By analysing the petiolule‐like pulvinus (plp) mutant in M. truncatula at phenotypic level (breakstrength and shaking assays), microscopic level (scanning electron microscopy and cross‐sectional analyses) and molecular level (expression level and expression pattern analyses), we discovered that the loss of function of PLP leads to an absence of abscission zone (AZ) formation and PLP plays an important role in leaflet and petiole AZ differentiation. Microarray analysis indicated that PLP affects abscission process through modulating genes involved in hormonal homeostasis, cell wall remodelling and degradation. Detailed analyses led us to propose a functional model of PLP in regulating leaflet and petiole abscission. Furthermore, we cloned the PLP gene (MsPLP) from alfalfa and produced RNAi transgenic alfalfa plants to down‐regulate the endogenous MsPLP. Down‐regulation of MsPLP results in altered pulvinus structure with increased leaflet breakstrength, thus offering a new approach to decrease leaf loss during alfalfa haymaking process. [ABSTRACT FROM AUTHOR]

BACKGROUND: Alfalfa (Medicago sativa L) is one of the most planted crops worldwide primarily used to feed animals. The use of alfalfa in human diet as sprouts, infusions and nutritional supplements is rapidly gaining popularity. Despite this, allergenicity assessment of this novel plant food is largely lacking. RESULTS: Here, leaf protein extract of alfalfa was studied using a combined proteomics, Immunoglobulin E (IgE)‐binding inhibition assay and in silico approach to find potential allergens. We have identified and annotated 129 proteins using in‐gel digestion proteomics and Blast2Go suit. A search against COMPARE database, using the identified proteins as query sequences, revealed high similarity with several allergenic proteins. The Single Point Highest Inhibition Achievable assay (SPHIAa) performed on the multiplex FABER® allergy testing system confirmed the in silico results and showed some additional potential allergens. This approach allowed the detection of proteins in alfalfa leaves cross‐reacting with plant allergens from three different allergen families such as lipid transfer, thaumatin‐like and Bet v 1‐like protein families. In addition, the absence of structural determinants cross‐reacting with seed storage allergenic proteins and with animal allergens was recorded. CONCLUSION: This study reports for the first time potential allergenic proteins in alfalfa. The results suggest that this plant food can be safely introduced, as a protein‐rich supplement, in the diet of patients allergic to animal food allergens. Allergic patients towards certain plant food allergens need to be careful about consuming alfalfa because they might have allergic symptoms. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

For practical utilization in cultivated alfalfa, we designed two target sites (fused to sgRNA cassettes driven by I MtU6-6p i and I MtU6-5p i ) in the alfalfa reference genome according to the previous editing events in the diploid model (Figure 1h). Keywords: male sterile line; Medicago truncatula; Medicago sativa; gene editing; glucose-methanol-choline (GMC) oxidoreductase; NP1 EN male sterile line Medicago truncatula Medicago sativa gene editing glucose-methanol-choline (GMC) oxidoreductase NP1 613 615 3 04/11/22 20220401 NES 220401 Alfalfa ( I Medicago sativa i L.) is an important forage crop with high nutrient values. Male sterile line, Medicago truncatula, Medicago sativa, gene editing, glucose-methanol-choline (GMC) oxidoreductase, NP1. [Extracted from the article]

Modern metabolomic approaches that generate more comprehensive phytochemical profiles than were previously available are providing new opportunities for understanding plant‐animal interactions. Specifically, we can characterize the phytochemical landscape by asking how a larger number of individual compounds affect herbivores and how compounds covary among plants. Here we use the recent colonization of alfalfa (Medicago sativa) by the Melissa blue butterfly (Lycaeides melissa) to investigate the effects of indivdiual compounds and suites of covarying phytochemicals on caterpillar performance. We find that survival, development time, and adult weight are all associated with variation in nutrition and toxicity, including biomolecules associated with plant cell function as well as putative anti‐herbivore action. The plant‐insect interface is complex, with clusters of covarying compounds in many cases encompassing divergent effects on different aspects of caterpillar performance. Individual compounds with the strongest associations are largely specialized metabolites, including alkaloids, phenolic glycosides, and saponins. The saponins are represented in our data by more than 25 individual compounds with beneficial and detrimental effects on L. melissa caterpillars, which highlights the value of metabolomic data as opposed to approaches that rely on total concentrations within broad defensive classes. [ABSTRACT FROM AUTHOR]

Summary: Alfalfa (Medicago sativa L.) is one of the most important forage crops worldwide. As a perennial, alfalfa is cut several times each year. Farmers face a dilemma: if cut earlier, forage nutritive value is much higher but regrowth is affected and the longevity of the stand is severely compromised. On the other hand, if alfalfa is cut later at full flower, stands persist longer and more biomass may be harvested, but the nutritive value diminishes. Alfalfa is a strict long‐day plant. We reasoned that by manipulating the response to photoperiod, we could delay flowering to improve forage quality and widen each harvesting window, facilitating management. With this aim, we functionally characterized the FLOWERING LOCUS T family of genes, represented by five members: MsFTa1, MsFTa2, MsFTb1, MsFTb2 and MsFTc. The expression of MsFTa1 correlated with photoperiodic flowering and its down‐regulation led to severe delayed flowering. Altogether, with late flowering, low expression of MsFTa1 led to changes in plant architecture resulting in increased leaf to stem biomass ratios and forage digestibility. By manipulating photoperiodic flowering, we were able to improve the quality of alfalfa forage and management, which may allow farmers to cut alfalfa of high nutritive value without compromising stand persistence. [ABSTRACT FROM AUTHOR]

Alfalfa, Medicago sativa L. (Fabaceae), is a highly preferred host plant of Lygus spp. (Hemiptera: Miridae). As such, intercropping alfalfa trap‐crops in strawberry production can serve as a sink for both Lygus (primarily Lygus hesperus Knight) and its natural enemies. Here we investigated the population dynamics and dispersal characteristics of the generalist predator complex in strawberry fields with alfalfa trap‐crops spaced 50 rows (62 m) apart. Predator abundance was determined by counting six focal taxa collected from strawberry and alfalfa. The data revealed that Orius spp. (Hemiptera: Anthocoridae) were the numerically dominant predator taxa, comprising 84% of the focal predator population. In general, the population densities obtained for the various taxa throughout this agroecosystem were unexpectedly uniform. Predator movement from a central alfalfa trap‐crop row was determined using a protein mark–capture procedure. Most protein‐marked predator specimens were collected less than 2 m from the centrally marked alfalfa row, indicating that the trap‐crop often produces a predator sink. Results suggest that alfalfa is a useful cultural (trap‐cropping) and a biological (refuge for natural enemies) control tactic for managing Lygus spp. in strawberries. [ABSTRACT FROM AUTHOR]

Legume plants, in association with rhizobia, are gaining increasing interest for heavy metal rhizoremediation. This symbiotic interaction combines the advantages of rhizoremediation and soil nitrogen enrichment. In metal polluted soils, Ochrobactrum cytisi can elicit non‐fixing nodules on legumes, including Medicago sativa. Nodulation kinetics was much slower when M. sativa plants were inoculated with O. cytisi Azn6.2 compared with the natural symbiont Ensifer meliloti 1021 and nodules were ineffective in nitrogen fixation. A competition experiment was performed using alfalfa grown on heavy metals, and co‐inoculated with equal amounts of the metal‐sensitive E. meliloti 1021 and the metal‐resistant O. cytisi Azn6.2. When plants were inoculated in non‐polluted substrates, all nodules were formed by E. meliloti 1021. Nevertheless, under increasing metal concentrations, the number of nodules occupied by O. cytisi grew. At the highest metal concentration, all nodules were elicited by O. cytisi, suggesting that the resistant species can take the place of the natural symbiont. This fact has important ecological and environmental implications when proposing legume–rhizobia symbioses for rhizoremediation and highlights the need of selecting highly resistant rhizobia in order to be competitive in polluted soils. [ABSTRACT FROM AUTHOR]

Pollen viability affects the probability that a pollen grain deposited on a plant's stigma will produce a viable seed. Because a mature seed is needed before a gene flow event can occur, pollen viability will influence the risk of escape for genetically engineered (GE) crops.Pollen viability was measured at intervals for up to 2 h following removal of the pollen from the anthers. It was quantified at three temperatures and for different alfalfa varieties, including both conventional and Roundup Ready (RR) varieties. Pollen viability was assessed using in vitro germination.Time since removal from the anthers was the most prevalent factor affecting pollen viability in alfalfa. Pollen viability declined with increasing time at all three temperatures and for all varieties tested. Pollen viability was not affected by temperatures ranging between 25 and 37 °C and did not vary among plant varieties, including conventional and RR varieties.Bee foraging behaviour suggested pollen viability within the first 10 min following pollen removal from a flower to most affect seed production. Pollen longevity was predicted to have little impact on seed set and gene flow. Linking pollinator behaviour to pollen viability improved our understanding of its impact on gene flow risk. [ABSTRACT FROM AUTHOR]

Eleven laboratory‐scale trials were undertaken in different years where ryegrass (Lolium perenne L.) or lucerne (Medicago sativa L.) were ensiled with different concentrations of tannin extracts (quebracho, Schinopsis balansae Engl., mimosa, Acacia mearnsii DE WILD.), and the effects on protein degradation were assessed. The dry‐matter (DM) content in grass silages ranged between 186 and 469 g/kg and in lucerne silages between 187 and 503 g/kg. Tannin extract, either quebracho or mimosa, was applied at 0–30 g/kg forage DM. Commercial additives such as Lactobacillus plantarum, formic acid or hexamine + NaNO2 were applied in two of the grass trials and in six of the lucerne trials. Eight of the trials incorporated a maximum ensiling duration of 90 or 180 days in addition to replicates which were opened and evaluated at earlier stages. All trials included silages which were assessed after at least 49 days of anaerobic storage. The crude protein (CP) fraction A (non‐protein nitrogen, NPN) as proportion of total CP, served as the main indicator for proteolysis. In ryegrass, in general, the level of proteolysis was lower than in lucerne. A correlation of DM content in silages and degree of proteolysis was only evident for ryegrass. In both forages, the degradation of true protein slowed considerably after 24 days of ensiling. True protein was conserved most with the highest level of tannin extract addition. However, in lucerne, the combination of formate with lactobacilli was equally effective up to 330 g DM/kg, and deamination was further inhibited by formic acid compared to tannin extracts. [ABSTRACT FROM AUTHOR]

Small, mobile insects are notoriously challenging to track across landscapes and manage in agricultural fields. However, genetic differentiation among insect populations and host plants acquired through host‐associated differentiation could be exploited to infer movement within crop systems and damage potential. Although many insects exhibit host‐associated differentiation, management strategies for insect vectors of plant pathogens assume a homogenous population. Nevertheless, phenotypic changes derived from host‐associated differentiation could manifest in altered behavior or physiology affecting the likelihood of vector–pathogen–plant interactions, or the subsequent efficiency of pathogen transmission. We used SNPs to assess genotypic structure and host‐associated differentiation in the cowpea aphid, Aphis craccivora Koch (Hemiptera: Aphididae). To do so, we sampled A. craccivora across the Midwestern United States. from two host plants, alfalfa (Medicago sativa) and black locust (Robinia pseudoacacia)—putative source populations for winged migrants. Simultaneously, we sampled winged A. craccivora landing in pumpkin fields where they transmit viruses. Structure analyses supported host‐associated differentiation by identifying two major genotypic groups: an alfalfa group containing a single multilocus genotype and a locust group containing all others. Winged locust‐group aphids landed at a much greater magnitude within focal fields during year 2 than year 1, while those in the alfalfa group remained fairly consistent. Spatial autocorrelation analyses indicated locust‐group aphid movement was characterized by small‐scale dispersal during year 2, likely originating from populations within 10 km. We also detected strong temporal differences in colonization from the two host plants. Early in the summer, most winged aphids (79.4%) derived from the locust group, whereas late in the summer more (58.3%) were from the alfalfa group. Because early crop growth stages are more susceptible to damage from aphid‐vectored viruses, these data implicate locust as the more important source and illustrate how host‐associated differentiation can be used to track dispersal and inform management of heterogeneous pest populations. [ABSTRACT FROM AUTHOR]

BACKGROUND: Pea aphid (Acyrthosiphon pisum Harris) is one of the major pests in alfalfa crops, causing significant yield losses. (E)‐β‐farnesene (EβF), an alarm pheromone released by pea aphid, is generic to many species of aphids, and is used to minimize potential danger from predators and parasitoids by avoiding the source of the pheromone. RESULTS: In this study, EβF synthase gene was constructed into a plant expression vector, and overexpressed in alfalfa (Medicago sativa L.), with expression among transgenic lines confirmed by qRT‐PCR. Subcellular localization analysis showed that EβF synthase gene was expressed in the plasma membrane and nucleus of the leaf. GC/MS of extraction from transgenic alfalfa indicated emission of EβF ranging from 5.92 to 13.09 ng day−1 g−1 fresh tissue. Behavior assays in Y‐olfactometers demonstrated that transgenic alfalfa expressing AaEβF gene could repel pea aphids, with aphids taking a significantly longer time to select a transgenic line compared with the control line (P < 0.01). CONCLUSION: We have demonstrated a potentially valuable strategy of using EβF synthase genes for aphid control in alfalfa. © 2018 Society of Chemical Industry This study explored that the ectopic expression of AaEβF induced the emission of (E)‐β‐farnesene in alfalfa. The emission affected the aphid behavior and repelled pea aphids from the transgenic alfalfa plants. [ABSTRACT FROM AUTHOR]

BACKGROUND: Bacteria with 1‐aminocyclopropane‐1‐carboxylate (ACC) deaminase activity could decrease the ethylene level, confer resistance of plant, and stimulate plant growth under biotic and abiotic stress conditions. RESULTS: Plant growth‐promoting rhizobacteria (PGPR) strains Enterobacter aerogenes (LJL‐5) and Pseudomonas aeruginosa (LJL‐13) were obtained from the rhizosphere of alfalfa grown under saline‐alkali conditions. The ACC deaminase activity of E. aerogenes (LJL‐5) and Ps. aeruginosa (LJL‐13) was approximately 2−5 µmol mg−1 h−1. indole acetic acid synthesis was increased with the increasing concentration of l‐tryptophan. Siderophore production and phosphate solubilization in Ps. aeruginosa (LJL‐13) were higher than those in E. aerogenes (LJL‐5). Compared to the non‐inoculated seedlings (1.31 ng mL−1 h−1), inoculated alfalfa seedlings with E. aerogenes (LJL‐5) (0.90 ng mL−1 h−1) and Ps. aeruginosa (LJL‐13) (0.78 ng mL−1 h−1) emitted lower levels of ethylene. Under saline‐alkali conditions in the greenhouse, inoculation with E. aerogenes (LJL‐5) and Ps. aeruginosa (LJL‐13) increased the biomass, soil and plant analyzer development (SPAD), and P content of alfalfa plants, and also induced the activity of antioxidant enzymes (superoxide dismutase, peroxidase and catalase), promoted the accumulation of antioxidant substances and removed various harmful substances. Under saline‐alkali conditions in the field (2012, 2013, and 2014), inoculation of alfalfa with E. aerogenes (LJL‐5) and Ps. aeruginosa (LJL‐13) significantly increased the shoot height, fresh and dry weights, yield and crude protein content of alfalfa plants, but decreased the fiber content. CONCLUSION: Two PGPR strains were isolated from the rhizosphere of alfalfa in saline‐alkali conditions. Both strains could promote alfalfa growth in saline‐alkali soil, and could be used as biofertilizer to promote plant growth under stress and reduce environmental pollution caused by fertilizers simultaneously. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Cadmium (Cd) is a non‐essential, toxic heavy metal that poses serious threats to both ecosystems and human health. Plants employ various cellular and molecular mechanisms to minimise the impact of Cd toxicity and cell walls function as a defensive barrier during Cd exposure.In this study, we adopted a quantitative gel‐based proteomic approach (two‐dimensional difference gel electrophoresis) to investigate changes in the abundance of cell wall and soluble proteins in stems of Medicago sativa L. upon long‐term exposure to Cd (10 mg·Cd·kg−1 soil as CdSO4). Obtained protein data were complemented with targeted gene expression analyses.Plants were affected by Cd exposure at an early growth stage but seemed to recover at a more mature stage as no difference in biomass was observed. The accumulation of Cd was highest in roots followed by stems and leaves. Quantitative proteomics revealed a changed abundance for 179 cell wall proteins and 30 proteins in the soluble fraction upon long‐term Cd exposure. These proteins are involved in cell wall remodelling, defence response, carbohydrate metabolism and promotion of the lignification process.The data indicate that Cd exposure alters the cell wall proteome and underline the role of cell wall proteins in defence against Cd stress. The identified proteins are linked to alterations in cell wall structure and lignification process in stems of M. sativa, underpinning the function of the cell wall as an effective barrier against Cd stress. [ABSTRACT FROM AUTHOR]

Abstract: Despite accumulating evidence that evolution can be predictable, studies quantifying the predictability of evolution remain rare. Here, we measured the predictability of genome‐wide evolutionary changes associated with a recent host shift in the Melissa blue butterfly (Lycaeides melissa). We asked whether and to what extent genome‐wide patterns of evolutionary change in nature could be predicted (i) by comparisons among instances of repeated evolution and (ii) from SNP × performance associations in a laboratory experiment. We delineated the genetic loci (SNPs) most strongly associated with host use in two L. melissa lineages that colonized alfalfa. Whereas most SNPs were strongly associated with host use in none or one of these lineages, we detected a an approximately twofold excess of SNPs associated with host use in both lineages. Similarly, we found that host‐associated SNPs in nature could also be partially predicted from SNP × performance (survival and weight) associations in a laboratory rearing experiment. But the extent of overlap, and thus degree of predictability, was somewhat reduced. Although we were able to predict (to a modest extent) the SNPs most strongly associated with host use in nature (in terms of parallelism and from the experiment), we had little to no ability to predict the direction of evolutionary change during the colonization of alfalfa. Our results show that different aspects of evolution associated with recent adaptation can be more or less predictable and highlight how stochastic and deterministic processes interact to drive patterns of genome‐wide evolutionary change. [ABSTRACT FROM AUTHOR]

Breeding for enhanced quality in lucerne ( Medicago sativa) frequently involves selection for higher leaf-to-stem ratio, multifoliolate leaves or short-internode stems. Three populations selected for such alternative morphologies and a reference cultivar were evaluated for forage yield, leaf-to-stem ratio and protein and fibre concentrations in leaves, stems and whole plants. Four managed environments were obtained by combining two stress levels (moderate or nil) with two sowing times. The population selected for high leaf-to-stem ratio, as well as the short-internode population, had highest leaf-to-stem ratio (1.27) across six harvests in two non-stress environments. The latter population had higher stem protein (12.9%) and lower stem neutral-detergent fibre ( NDF) concentration (58.7%) than other populations. The multifoliolate population had intermediate quality, showing low expression of the multifoliolate trait (14.0% across four environments), particularly under stress (10.5%). The autumn-sown, fully irrigated environment had, on average, highest dry-matter yield (4.19 t ha−1) and lowest leaf-to-stem ratio (0.74). Drought-stressed environments had lower plant NDF (−12.3% on average) and leaf protein (−9.7%), and higher stem protein (+8.6%) than fully irrigated environments. The results suggested that environmental effects might have greater impact on quality than genetic effects, even for a population set including material selected for quality-driven morphology. [ABSTRACT FROM AUTHOR]

Root border cells lie on the surface of the root cap and secrete massive amounts of mucilage that contains polysaccharides and proteoglycans. Golgi stacks in the border cells have hypertrophied margins, reflecting elevated biosynthetic activity to produce the polysaccharide components of the mucilage. To investigate the three-dimensional structures and macromolecular compositions of these Golgi stacks, we examined high-pressure frozen/freeze-substituted alfalfa root cap cells with electron microscopy/tomography. Golgi stacks in border cells and peripheral cells, precursor cells of border cells, displayed similar morphological features, such as proliferation of trans cisternae and swelling of the trans cisternae and trans-Golgi network ( TGN) compartments. These swollen margins give rise to two types of vesicles larger than other Golgi-associated vesicles. Margins of trans-Golgi cisternae accumulate the LM8 xylogalacturonan ( XGA) epitope, and they become darkly stained large vesicles ( LVs) after release from the Golgi. Epitopes for xyloglucan ( XG), polygalacturonic acid/rhamnogalacturonan-I ( PGA/ RG-I) are detected in the trans-most cisternae and TGN compartments. LVs produced from TGN compartments ( TGN- LVs) stained lighter than LVs and contained the cell wall polysaccharide epitopes seen in the TGN. LVs carrying the XGA epitope fuse with the plasma membrane only in border cells, whereas TGN- LVs containing the XG and PGA/ RG-I epitopes fuse with the plasma membrane of both peripheral cells and border cells. Taken together, these results indicate that XGA is secreted by a novel type of secretory vesicles derived from trans-Golgi cisternae. Furthermore, we simulated the collapse in the central domain of the trans-cisternae accompanying polysaccharide synthesis with a mathematical model. [ABSTRACT FROM AUTHOR]

Semi-hybrids between genetically distant alfalfa ( Medicago sativa subsp. sativa) populations may display heterosis whose extent is affected by the structure of genetic diversity across populations. This study aimed to assess the genetic diversity across three putative heterotic populations, one Italian, one Egyptian and one of semi-erect germplasm from Eastern Europe, Canada and Spanish Mielga (EECM population). Each population was bred from ten parents after various selection cycles. Fifteen genotypes per population were characterized by 20 polymorphic SSR markers. The among-population variance was over eightfold smaller than the average within-population variance (2.05 vs. 17.24) and accounted for 10.6% of the total variation. G'ST = .090 across markers indicated modest population differentiation. Various diversity measures, multidimensional scaling, and cluster analysis of the genetic structure indicated that the Italian population was more distant from the EECM population than the Egyptian one. The EECM and Egyptian populations were the most distant geographically and genetically. EECM displayed widest intrapopulation variation, accordingly to its constitutive geographical diversity. In conclusion, this study indicates modest genetic differentiation between alfalfa populations even for geographically distant germplasm. [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY:: The ability to attract pollinators is crucial to plants that rely on insects for pollination. We contrasted the roles of floral display size and flower color in attracting three bee species and determined the relationships between plant attractiveness (number of pollinator visits) and seed set for each bee species. METHODS:: We recorded pollinator visits to plants, measured plant traits, and quantified plant reproductive success. A zero‐inflated Poisson regression model indicated plant traits associated with pollinator attraction. It identified traits that increased the number of bee visits and traits that increased the probability of a plant not receiving any visits. Different components of floral display size were examined and two models of flower color contrasted. Relationships between plant attractiveness and seed set were determined using regression analyses. KEY RESULTS:: Plants with more racemes received more bee visits from all three bee species. Plants with few racemes were more likely not to receive any bee visits. The role of flower color varied with bee species and was influenced by the choice of the flower color model. Increasing bee visits increased seed set for all three bee species, with the steepest slope for leafcutting bees, followed by bumble bees, and finally honey bees. CONCLUSIONS:: Floral display size influenced pollinator attraction more consistently than flower color. The same plant traits affected the probability of not being visited and the number of pollinator visits received. The impact of plant attractiveness on female reproductive success varied, together with pollinator effectiveness, by pollinator species. [ABSTRACT FROM AUTHOR]

Nitrogen (N) leaching from soil into water is a significant concern for intensively grazed forage-based systems because it can cause a decline in water quality and is a risk to human health. Urine patches from grazing animals are the main source of this N. The objective of this study was to quantify the effect that forage type and gibberellic acid ( GA) application had on N leaching and herbage N uptake from urine patches on perennial ryegrass-white clover ( RGWC), Italian ryegrass and lucerne. A lysimeter study was conducted over 17 months to measure herbage growth, N uptake and N loss to water beneath each of the three forage types with the following treatments: control, urine (700 kg N/ha) and urine with GA (8 g GA active ingredient/ha). Compared with RGWC (205 kg N/ha), N leaching losses were 35.3% lower from Italian ryegrass (133 kg N/ha) and 98.5% higher from lucerne (407 kg N/ha). These differences in leaching loss are likely to be due to winter plant growth and N uptake. During the winter months, Italian ryegrass had higher N uptake, whereas lucerne had lower N uptake, compared with RGWC. The application of GA had no effect on N leaching losses, DM yield or N uptake of forage treated with 700 kg N/ha urine. [ABSTRACT FROM AUTHOR]

Six dryland pastures were established at Lincoln University, Canterbury, New Zealand, in February 2002. Production and persistence of cocksfoot pastures established with subterranean, balansa, white or Caucasian clovers, and a perennial ryegrass-white clover control and a lucerne monoculture were monitored for nine years. Total annual dry-matter (10.0-18·5 t DM ha−1) and sown legume yields from the lucerne monoculture exceeded those from the grass-based pastures in all but one year. The lowest lucerne yield (10 t ha−1 yr−1) occurred in Year 4, when spring snow caused ungrazed lucerne to lodge and senesce. Cocksfoot with subterranean clover was the most productive grass-based pasture. Yields were 8·7-13·0 t DM ha−1 annually. Subterranean clover yields were 2·4-3·7 t ha−1 in six of the nine years which represented 26-32% of total annual production. In all cocksfoot-based pastures, the contribution of sown pasture components decreased at a rate equivalent to 3·3 ± 0·05% per year ( R2 = 0·83) and sown components accounted for 65% of total yield in Year 9. In contrast, sown components represented only 13% of total yield in the ryegrass-white clover pastures in Year 9, and their contribution declined at 10·1 ± 0·9% per year ( R2 = 0·94). By Year 9, 79% of the 6.6 t ha−1 produced from the ryegrass-white clover pasture was from unsown species and 7% was dead material. For maximum production and persistence, dryland farmers on 450-780 mm yr−1 rainfall should grow lucerne or cocksfoot-subterranean clover pastures in preference to ryegrass and white clover. Inclusion of white clover as a secondary legume component to sub clover would offer opportunities to respond to unpredictable summer rainfall after sub clover has set seed. [ABSTRACT FROM AUTHOR]

We evaluated the effect of row spacing on seed and forage yields in alfalfa ( Medicago sativa L.) using combined seed and forage production plots, in an irrigated Mediterranean agricultural environment. We compared three row distances (20, 40 and 60 cm) in two cultivars at a seed rate of 25 kg ha−1 over a period of 4 years. We measured the seed yield and yield components as well as forage production. The 4-year average revealed an overall clean seed yield of 367 kg ha−1 declining over time, without significant differences in row distances. The number of shoots per square metre differed significantly as a function of row spacing, with averages of 357, 226 and 172 shoots m−2 for row widths of 20, 40 and 60 cm respectively. The row spacing did not affect the number of racemes per shoot (23·1), the number of pods per raceme (7·2), the number of seeds per pod (6·5) or the thousand seed weight (1·667 g). The average forage production was 20·1, 18·5 and 17·9 Mg DM ha−1 for row distances of 20, 40 and 60 cm, respectively, with higher yields associated with smaller row distances. Our data demonstrate that row spacing >20 cm does not confer any advantage to the production of alfalfa seed under irrigated Mediterranean agricultural conditions and that close spacing can significantly increase forage yields in the same environment. [ABSTRACT FROM AUTHOR]

Various types of protein-spray solutions have proven effective for externally tagging arthropods for mark-release-recapture and mark-capture type dispersal research. However, there is concern that certain standardized arthropod collection methods, such as sweep netting, might lead to high incidences of protein transfer from field-marked to unmarked arthropods during sample collection and sample handling. Native arthropods were collected in sweep nets from a field of alfalfa, Medicago sativa L. ( Fabaceae). The nets also contained 10 egg white-, 10 bovine milk-, 10 soy milk-, and 10 water (control)-marked Hippodamia convergens Guérin- Méneville ( Coleoptera: Coccinellidae) that were visually distinguishable by a yellow, white, green, and blue dot, respectively. The plant debris and arthropods from each sweep net collection were then placed into either a paper or a plastic bag and frozen for storage. The contents of each sweep net sample were thawed and the color-coded H. convergens and field-collected arthropods were examined for the presence of each protein by an egg white (albumin), bovine milk (casein), and soy milk (soy trypsin) enzyme-linked immunosorbent assay ( ELISA). Data revealed that only 0.67, 0.81, and 0% of the field-collected unmarked arthropods acquired an egg white, bovine milk, and soy milk mark, respectively. ELISA results also showed that all the egg white-marked H. convergens retained their mark, but 22.1% of the bovine milk-marked and 5.1% of the soy milk-marked H. convergens (color-coded beetles) lost their mark during the collection and sample handling processes. [ABSTRACT FROM AUTHOR]

BACKGROUND:Environmentally friendly agriculture needs toreduce the useof synthetic fertilizers andto reclaim nutrients from organicwastes. In this study the effect of five doses (0, 12, 24, 48 and 96 t ha-1) of two two-phase olivemillwaste (TPOMW)-based composts on the bioactivity and chemical characteristics of an agricultural soil and their potential to fertilize alfalfa (Medicago sativa) and stimulate nodulation were assessed during a two-year incubation experiment. The two composts were prepared either with the olive mill waste alone (compost A), which served as control, or mixed with a liquid fatty-proteinaceous hydrolyzate waste (FPH) fromthe pharmaceutical industry (compost AH). Compost AH resulted in greater N immobilization than compost A because the former supplied the soil with easily degradable C and N, which increased microbial biomass and activity. Both compost mineralizations during the first year of incubation supplied the soilwithmore nutrients (mainly N),more sowithAthan with AH.Nevertheless, plant growthwas similar in soils amendedwith either A or AH. Both composts induced nodulation similarly and the highest dose (96 t ha-1) increased the formation of nodules by a factor of 11 compared with the four lower doses. CONCLUSION: TPOMWserves as aneffective groundmaterial for co-compostingwith liquidwastes such as FPH. TPOMWsupplies key nutrients and stimulates nodulation in alfalfa. [ABSTRACT FROM AUTHOR]

Predicted increases in atmospheric carbon dioxide ( CO2) concentrations could modify crop resistance to insect herbivores by altering plant quality. The short generation times of aphids may allow them to exploit such changes and colonise previously resistant plant genotypes. Lucerne ( Medicago sativa) has undergone global selective breeding against aphids, including the pea aphid, Acyrthosiphon pisum. The purpose of this study was to characterise how ambient CO2 ( aCO2) and elevated ( eCO2) (400 and 600 µmol mol−1, respectively) affected plant physiological traits potentially linked to aphid resistance, focussing on foliar amino acid concentrations, across five M. sativa genotypes with varying resistance to A. pisum. These included susceptible (Hunter River), low (Trifecta), moderate (Aurora and Genesis) and high resistance (Sequel). Under eCO2, root nodulation doubled and essential amino acid concentrations increased by 86% in resistant Sequel, whereas essential amino acid concentrations decreased by 53% in Genesis. Moreover, concentrations of lysine, an amino acid whose deficiency has been linked previously to A. pisum resistance in M. sativa, increased by 127% in Sequel at eCO2. Compared with aCO2, aphid colonisation of Sequel plants rose from 22% to 78% and reproduction rates increased from 1.1 to 4.3 nymphs week−1 under eCO2 conditions. In contrast, Genesis became more resistant at eCO2 compared with plants at aCO2; aphid colonisation rates fell from 78% to 44% of plants and reproductive rates decreased from 4.9 to 1.7 nymphs week−1. In conclusion, predicted changes in atmospheric CO2 concentrations could either reduce (Sequel) or enhance (Genesis) resistance to aphids, which might be linked to quantitative and qualitative changes in foliar amino acids. [ABSTRACT FROM AUTHOR]

ABSTRACT There has been increasing use of live vegetation in laboratory experiments, in particular in fluvial geomorphology. The results from these studies have provided useful insight into the role that vegetation plays in impacting and modifying geomorphic systems. However there has been little published on the seed preparation techniques and vegetation growing conditions required for use in these experiments. This commentary presents results from a series of experiments investigating these factors using Medicago sativa and Avena Sativa, with the aim of highlighting the optimal growing conditions found to provide a starting point for researchers interested in implementing these techniques. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Alfalfa is a widely distributed forage legume whose leaves are high in protein content and whose stems are suitable for bioethanol production. However, alfalfa forage digestibility, quality and yield may vary under future climate change scenarios. This legume can establish double symbiosis with nitrogen-fixing bacteria and arbuscular mycorrhizal fungi ( AMF). The presence of AMF can modify the evolution of biomass production and partitioning during the vegetative growth of alfalfa. We hypothesised that mycorrhizal symbiosis may change the quantity and/or quality of carbohydrates and lignin in leaves and/or stems of alfalfa, with these changes being dependent on the atmospheric CO2 concentration at which plants are grown. Results showed that mycorrhizal alfalfa plants exposed to elevated CO2 had improved leaf, stem and root biomass, enhanced amount of hemicellulose and decreased concentration of lignin in cell walls of leaves as well as increased levels of glucose and fructose in stems compared with non-mycorrhizal alfalfa. These results indicated improved forage quality (leaves) and enhanced potential for bioethanol conversion (stems) in mycorrhizal alfalfa cultivated under elevated CO2. Moreover, the potential of stems for producing CH4 reinforced their suitability for the conversion of biomass into bioethanol. [ABSTRACT FROM AUTHOR]

Alfalfa is a widely distributed forage legume whose leaves are high in protein content and whose stems are suitable for bioethanol production. However, alfalfa forage digestibility, quality and yield may vary under future climate change scenarios. This legume can establish double symbiosis with nitrogen-fixing bacteria and arbuscular mycorrhizal fungi ( AMF). The presence of AMF can modify the evolution of biomass production and partitioning during the vegetative growth of alfalfa. We hypothesised that mycorrhizal symbiosis may change the quantity and/or quality of carbohydrates and lignin in leaves and/or stems of alfalfa, with these changes being dependent on the atmospheric CO2 concentration at which plants are grown. Results showed that mycorrhizal alfalfa plants exposed to elevated CO2 had improved leaf, stem and root biomass, enhanced amount of hemicellulose and decreased concentration of lignin in cell walls of leaves as well as increased levels of glucose and fructose in stems compared with non-mycorrhizal alfalfa. These results indicated improved forage quality (leaves) and enhanced potential for bioethanol conversion (stems) in mycorrhizal alfalfa cultivated under elevated CO2. Moreover, the potential of stems for producing CH4 reinforced their suitability for the conversion of biomass into bioethanol. [ABSTRACT FROM AUTHOR]

Climate change can affect species directly and indirectly by altering interactions between species within communities. These indirect effects can ramify through a community and affect many species, including some that may not have been directly affected by the perturbation. Identifying these chains of indirect effects is difficult, and most studies only follow indirect effects across two or three species. Here, we use a factorial field experiment to demonstrate that precipitation affects spotted aphids through a complex chain of indirect interactions that are mediated by other herbivores and a generalist predator. We experimentally simulated drought, which reduced water content in alfalfa plants. While water stress in alfalfa had no direct effect on spotted aphids, it lowered the population growth rate of pea aphids, another common alfalfa pest. Because ladybeetle predators were attracted to high pea aphid densities, predator densities were lower in drought treatments. Consequently, spotted aphid densities were released from top-down control (apparent competition) in drought treatments and reached densities three times higher than spotted aphids in ambient treatments with high pea aphid densities. Thus, drought affected spotted aphids in the interaction chain: drought --» alfalfa --> pea aphids --> predators --» spotted aphids. This result illustrates the lengthy path that indirect effects of climate change may take through a community, as well as the importance of community-level experiments in determining the net effect of climate change. [ABSTRACT FROM AUTHOR]

Lucerne or alfalfa Medicago sativa is the most important temperate forage legume worldwide. Only one or two varieties of lucerne were grown in the U.S.A. and Australia (the two leading exporters of lucerne) before the late 1950s and late 1970s, respectively. These dates coincided with the arrival of aphid species, which devastated lucerne stands and prompted the development of aphid resistant cultivars., Lucerne-feeding aphids, including bluegreen aphids Acyrthosiphon kondoi, pea aphids Acyrthosiphon pisum, spotted alfalfa aphids Therioaphis trifolii maculata and cowpea aphids Aphis craccivora, however, still present significant risks for the lucerne industry worldwide and account for 25% of global production losses. Moreover, increased production costs, negative environmental effects and emerging aphid resistance to insecticide applications have led to a narrowing of management options against lucerne aphids., Understanding lucerne aphid biology and trophic ecology will be needed to develop future management practices, including biological control. We review and synthesize research on the four lucerne aphid species, focussing on cultivar resistance and their interactions with other organisms, including predators, parasitoids, entomopathogens and bacterial symbionts. The effects of global climate change are considered, with a particular emphasis on the potential for compromised aphid resistance in lucerne cultivars under future climates., We conclude by identifying future research questions and perspectives for the sustainable management of lucerne aphids. These include the characterization of plant secondary metabolites associated with natural enemy recruitment, an understanding of the role of endosymbionts in cultivar resistance and a better comprehension of multi-trophic interactions of lucerne aphids, both with other herbivores and higher trophic groups. [ABSTRACT FROM AUTHOR]

BACKGROUND In previous research, two alfalfa clonal lines (252 and 1283) were identified that exhibited environmentally stable differences in stem cell walls. Compared with stems of 1283, stems of 252 have a higher cell wall concentration and greater amounts of lignin and cellulose but reduced levels of pectic sugar residues. These results suggest greater deposition of secondary xylem and a reduction in pith in stems of 252 compared with 1283. RESULTS The stem morphology and anatomy of first-cut and second-cut harvests of field-grown 1283 and 252 were examined. For both harvests, stems of 1283 were thicker and had a higher leaf/stem ratio compared with stems of 252. Stem cross-sections of both genotypes were stained for lignin, and the proportions of stem area that were pith and secondary xylem were measured using ImageJ. Stems of 252 exhibited greater deposition of secondary xylem and a reduction in pith proportion compared with stems of 1283 for the first-cut harvest, but this difference was not statistically significant for the second-cut harvest. CONCLUSION The results indicate that the proportions of secondary xylem and pith are not environmentally stable in these two genotypes and hence cannot be the sole basis for the differences in cell wall concentration/composition. © 2012 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Maternally inherited facultative endosymbiotic bacteria are common among insects, including many polyphagous insect herbivores. To investigate whether symbiont infection is structured by host plant in the polyphagous aphid Aphis craccivora Koch, pyrosequencing and diagnostic PCR were performed on 26 populations from two different host plants, alfalfa ( Medicago sativa) or black locust ( Robinia pseudoacacia). Results indicated that Aphis craccivora harbours distinctly different microbial communities in alfalfa versus locust. The facultative symbiont Hamiltonella was found only in aphids collected from alfalfa, and the facultative symbiont Arsenophonus was found only in aphids from locust. Hamiltonella is known to protect aphids against hymenopteran parasitoids, whereas the phenotypic effects of Arsenophonus in aphids are unknown. Correspondingly, a screen of the aphid samples for hymenopteran DNA indicated that Hamiltonella-bearing alfalfa populations of A. craccivora experienced lower parasitism than Arsenophonus-bearing locust populations. This study contributes to the growing body of evidence that correlative associations between bacterial endosymbionts and host plants may be a common phenomenon in polyphagous herbivores, and suggests that microbial symbionts have the potential to act as drivers for observed ecological differences among host-associated populations of polyphagous insects. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) present serious problems in the environment because they may affect negatively human health and alter native ecological communities. Phytoremediation has long been recognized as an efficient method of eliminating PAH pollutants from soil. A pot experiment was conducted in greenhouse conditions to investigate the capability of three plant species, Medicago sativa, Brassica napus, and Lolium perenne, to promote the degradation of pyrene by measuring their growth on pyrene-contaminated soils. After 90 days, pyrene concentration in soils declined by 32, 30, and 28%, respectively, with M. sativa, B. napus, and L. perenne, whereas it decreased only by 18% in the control soil without plants. These results indicated that pyrene was successfully removed by plants used. In particular, M. sativa showed the highest capacity for pyrene dissipation in soil, whereas L. perenne was more efficient in limiting adverse effects of pyrene contamination. In addition, the contaminant pyrene was undetectable in shoots and roots of the three species, likely because plant roots can stimulate soil microbial biomass and oxygen transport to the rhizosphere, thus facilitating indirectly the degradation process of pyrene. Further studies are in progress to evaluate the possible adsorption of pyrene to soil organic matter. [ABSTRACT FROM AUTHOR]

Optimizing sample processing, reducing the duration of the preparation of specimen, and adjusting procedures to adhere to new health and safety regulations, are the current challenges of plant electron microscopists. To address these issues, plant processing protocols for TEM, combining the use of polyphenolic compounds as substitute for uranyl acetate with microwave technology are being developed. In the present work, we optimized microwave-assisted processing of different types of plant tissue for ultrastuctural and immunocytochemical studies. We also explored Oolong tea extract as alternative for uranyl acetate for the staining of plant samples. We obtained excellent preservation of cell ultrastructure when samples were embedded in epoxy resin, and of cell antigenicity, when embedded in LR-White resin. Furthermore, Oolong tea extract successfully replaced uranyl acetate as a counterstain on ultrathin sections, and for in block staining. These novel protocols reduce the time spent at the bench, and improve safety conditions for the investigator. The preservation of the cell components when following these approaches is of high quality. Altogether, they offer significant simplification of the procedures required for electron microscopy of plant ultrastructure. [ABSTRACT FROM AUTHOR]

•Premise of the study: Although there is growing evidence that autopolyploidy is a widespread and important evolutionary phenomenon, it has received less attention than allopolyploidy. Medicago sativa comprises several diploid and autopolyploid taxa, including autotetraploid cultivated alfalfa, and affords an opportunity to elucidate the evolutionary history of a morphologically and genetically complex autopolyploid system. • Methods: Phylogenies and haplotype networks were constructed from two chloroplast noncoding regions ( rp120 - rps12 and trnS - trnG spacers) across seven diploid and polyploid infraspecific taxa of M. sativa and five additional closely related Medicago species, and genetic differentiation was estimated. • Key results: The two most prominent M. sativa autopolyploids have contrasting evolutionary histories. Chloroplast data support a simple autopolyploid origin of subsp. sativa (alfalfa) from diploid subsp. caerulea , from which it is distinguishable in several quantitative characters. In contrast, morphologically identical diploid and autopolyploid cytotypes of subsp. falcata were found to possess very different chloroplast haplotypes, suggesting past introgression from M. prostrata into the polyploid. Despite the presence of hybrids between tetraploid subspecies falcata and sativa , there was little evidence of introgression of chloroplast genomes from either subspecies into the other. • Conclusions: Autopolyploid evolution in M. sativa is complicated and has followed very different paths in different subspecific taxa. The potential exists for gene flow in virtually all combinations of subspecies both within and between ploidies, yet despite the existence of hybrids, morphologically and genetically distinctive subspecies persist. [ABSTRACT FROM AUTHOR]

Meiss H, Médiène S, Waldhardt R, Caneill J, Bretagnolle V, Reboud X & Munier-Jolain N (2010). Perennial lucerne affects weed community trajectories in grain crop rotations. Weed Research 50, 331–340. Complex crop rotations may be beneficial for weed management. We analysed how pluriannual forage crops may affect weed composition during cereal-based crop rotations. Using a space-for-time-substitution design, we compared weed composition and diversity before, during and after perennial crops. We surveyed four groups of fields: (a) winter wheat ( Triticum aestivum L.) following annual crops, (b) 1-year old lucerne ( Medicago sativa L.) following annual crops, (c) 2–6 years old lucerne and (d) winter wheat following pluriannual lucerne in western France (420 fields in total). Weed composition varied among the four groups, suggesting a cyclic trajectory corresponding to the phases of the crop rotation. Indicator Species Analysis showed that these differences were due to at least 40 species, including the most common weeds. A functional group analysis showed that perennial lucerne crops shifted the communities away from several problematic weeds, especially annual broad-leaved species with an upright or climbing morphology. This effect was also visible in the wheat following lucerne. Other species (including perennials, annuals with rosettes and some grasses) benefited from the particular growth conditions in lucerne but decreased in the following wheat. The diversification of arable crop rotations with perennial crops may thus be useful for Integrated Weed Management, reducing the need for herbicides. Other species less harmful to annual crops were favoured, resulting in increased floristic diversity. [ABSTRACT FROM AUTHOR]

Aphanomyces euteiches and Phytophthora medicaginis are two pathogens of seedling and mature alfalfa ( Medicago sativa L.) that are frequently found in the same field sites. In order to investigate possible interactions of these two pathogens, two greenhouse experiments were conducted on seedling alfalfa from check populations representing the phenotypic classes of dual susceptibility and dual resistance to both pathogens. Seedlings were challenged with multiple inoculum concentrations of A. euteiches and P. medicaginis. Separate real-time PCR assays specific for A. euteiches and P. medicaginis were used to quantify the amount of each pathogen in root tissue. For both pathogens, significantly more pathogen DNA was detected in the susceptible check population Saranac than in the resistant check population WAPH-1 in all treatment combinations. In general, co-inoculation with both A. euteiches and P. medicaginis resulted in significantly reduced amounts of P. medicaginis DNA detected when compared with amounts detected from inoculations with P. medicaginis alone. This relationship was observed for the analysis of bulked plant samples and also for individual plants. Co-infestation by both pathogens did not reduce the quantity of A. euteiches detected. Possible mechanisms responsible for the inhibition of accumulation of P. medicaginis by A. euteiches are discussed. [ABSTRACT FROM AUTHOR]

In North African oases Medicago sativa ssp. sativa is likely to have been cultivated for long time without contacts with ssp. falcata. In order (i) to verify the genetic distinctiveness of the alfalfa germplasm of the oasis and (ii) to examine their internal variation, 17 farm landraces were collected in Siwa oasis (Egypt) and studied with four Egyptian and three Italian cultivars (120 plants/population) by means of bio-agronomic characters in 2 years cultivation and SSR markers in ‘bulk’ samples. Siwa germplasm was similar to the cultivars for dry matter yield but differed for plant form, earliness and reaction to fall conditions; SSR analysis based on 31 polymorphic DNA fragments distinguished Siwa landraces from the two groups of varieties. The variation within Siwa group was of continuous type based on bio-agronomic traits; average genetic similarity was high (0.8959) and UPGMA dendrogram suggests poor isolation among the landraces, although all, except two, were uniquely fingerprinted. The use of putative ‘pure’ subspecies of high agronomic value in the alfalfa variety construction process is discussed. [ABSTRACT FROM AUTHOR]