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BACKGROUND: Arbuscular mycorrhizal fungi (AMF) form mutualistic symbioses with c. two-thirds of all land plants. Traditionally, it was thought that they played no role in nitrogen (N) acquisition for their host, despite early evidence to the contrary. More recently, this perception has changed radically, with the demonstration that AMF can acquire N from both inorganic and organic N sources and transfer some of this N to their host plant. SCOPE: This review discusses the current evidence for AMF N uptake, transport and plant transfer under different experimental conditions and highlights key questions that remain to be resolved. The relevance of this AMF N acquisition pathway is discussed both in relation to host plant and fungal N nutrition. The importance of interactions with the soil community and subsequent implications for soil N cycling are also highlighted. CONCLUSIONS: Reported AMF contribution to plant N varies widely, but the reasons for this variability are unclear. In low N systems even small amounts of ‘extra’ N may confer the plant with a competitive advantage, but it is also likely that competition for N between symbionts occurs. To advance this area, a more mechanistic approach is required that treats the fungus as a Darwinian organism rather than a mere extension of the plant. Application of genomics and metabolomics technologies to this topic should enable resolution of some of the key questions outlined in this review.

Nitrous oxide (N2O) is a potent, globally important, greenhouse gas, predominantly released from agricultural soils during nitrogen (N) cycling. Arbuscular mycorrhizal fungi (AMF) form a mutualistic symbiosis with two-thirds of land plants, providing phosphorus and/or N in exchange for carbon. As AMF acquire N, it was hypothesized that AMF hyphae may reduce N2O production. AMF hyphae were either allowed (AMF) or prevented (nonAMF) access to a compartment containing an organic matter and soil patch in two independent microcosm experiments. Compartment and patch N2O production was measured both before and after addition of ammonium and nitrate. In both experiments, N2O production decreased when AMF hyphae were present before inorganic N addition. In the presence of AMF hyphae, N2O production remained low following ammonium application, but increased in the nonAMF controls. By contrast, negligible N2O was produced following nitrate application to either AMF treatment. Thus, the main N2O source in this system appeared to be via nitrification, and the production of N2O was reduced in the presence of AMF hyphae. It is hypothesized that AMF hyphae may be outcompeting slow-growing nitrifiers for ammonium. This has significant global implications for our understanding of soil N cycling pathways and N2O production.

Worldwide, wild boar (Sus scrofa) and feral pigs are involved in environmental damage and disease transmission. These impacts are often associated with relatively high local densities of pigs, so the monitoring of population trends is important. Dung counts can be used to estimate population trends, but knowledge of daily defecation rates (DDRs) is needed to estimate absolute numbers. To address this issue, we calculated the DDRs of 18 captive, adult wild boar in July 2005 and November 2007. The mean DDR was 3.8–4.3 dung/boar/day, depending on the trial. We discuss the results by comparing the DDR of wild boar to that of other ungulates and omnivores, and we consider the implications of these results for estimating feral pig and wild boar density through dung counts.

Nitrous oxide (N 2 O) is a potent, globally important, greenhouse gas, predominantly released from agricultural soils during nitrogen (N) cycling. Arbuscular mycorrhizal fungi ( AMF ) form a mutualistic symbiosis with two‐thirds of land plants, providing phosphorus and/or N in exchange for carbon. As AMF acquire N, it was hypothesized that AMF hyphae may reduce N 2 O production. AMF hyphae were either allowed ( AMF ) or prevented (non AMF ) access to a compartment containing an organic matter and soil patch in two independent microcosm experiments. Compartment and patch N 2 O production was measured both before and after addition of ammonium and nitrate. In both experiments, N 2 O production decreased when AMF hyphae were present before inorganic N addition. In the presence of AMF hyphae, N 2 O production remained low following ammonium application, but increased in the non AMF controls. By contrast, negligible N 2 O was produced following nitrate application to either AMF treatment. Thus, the main N 2 O source in this system appeared to be via nitrification, and the production of N 2 O was reduced in the presence of AMF hyphae. It is hypothesized that AMF hyphae may be outcompeting slow‐growing nitrifiers for ammonium. This has significant global implications for our understanding of soil N cycling pathways and N 2 O production.

Nitrous oxide (N2 O) is a potent, globally important, greenhouse gas, predominantly released from agricultural soils during nitrogen (N) cycling. Arbuscular mycorrhizal fungi (AMF) form a mutualistic symbiosis with two-thirds of land plants, providing phosphorus and/or N in exchange for carbon. As AMF acquire N, it was hypothesized that AMF hyphae may reduce N2 O production. AMF hyphae were either allowed (AMF) or prevented (nonAMF) access to a compartment containing an organic matter and soil patch in two independent microcosm experiments. Compartment and patch N2 O production was measured both before and after addition of ammonium and nitrate. In both experiments, N2 O production decreased when AMF hyphae were present before inorganic N addition. In the presence of AMF hyphae, N2 O production remained low following ammonium application, but increased in the nonAMF controls. By contrast, negligible N2 O was produced following nitrate application to either AMF treatment. Thus, the main N2 O source in this system appeared to be via nitrification, and the production of N2 O was reduced in the presence of AMF hyphae. It is hypothesized that AMF hyphae may be outcompeting slow-growing nitrifiers for ammonium. This has significant global implications for our understanding of soil N cycling pathways and N2 O production.Nitrous oxide (N2 O) is a potent, globally important, greenhouse gas, predominantly released from agricultural soils during nitrogen (N) cycling. Arbuscular mycorrhizal fungi (AMF) form a mutualistic symbiosis with two-thirds of land plants, providing phosphorus and/or N in exchange for carbon. As AMF acquire N, it was hypothesized that AMF hyphae may reduce N2 O production. AMF hyphae were either allowed (AMF) or prevented (nonAMF) access to a compartment containing an organic matter and soil patch in two independent microcosm experiments. Compartment and patch N2 O production was measured both before and after addition of ammonium and nitrate. In both experiments, N2 O production decreased when AMF hyphae were present before inorganic N addition. In the presence of AMF hyphae, N2 O production remained low following ammonium application, but increased in the nonAMF controls. By contrast, negligible N2 O was produced following nitrate application to either AMF treatment. Thus, the main N2 O source in this system appeared to be via nitrification, and the production of N2 O was reduced in the presence of AMF hyphae. It is hypothesized that AMF hyphae may be outcompeting slow-growing nitrifiers for ammonium. This has significant global implications for our understanding of soil N cycling pathways and N2 O production.

Nitrogen (N) is a vital plant element, affecting plant physiological processes, carbon and water fluxes and ultimately crop yields. However, N uptake by crops can vary over fine spatiotemporal scales, and optimising the application of N-fertiliser to maximise crop performance is challenging. To investigate the potential of spatially mapping the impact of N fertiliser application on crop physiological performance and yield, we leverage both optical and thermal data sampled from drone platforms and ground-level leaf measurements, across a range of different N, Sulphur (S) and sucrose treatments in winter wheat. Using leaf level hyperspectral reflectance data, leaf chlorophyll content was accurately modelled across fertiliser treatments via partial least squares regression (PLSR; R2 = 0.93, P < 0.001). Leaf photosynthetic capacity (Vcmax) exhibited a strong linear relationship with leaf chlorophyll (R2 = 0.77; P < 0.001). Using drone-acquired MERIS terrestrial chlorophyll index (MTCI) as a proxy for leaf chlorophyll (R2 = 0.76; P < 0.001), within field variations in Vcmax was spatially mapped at the centimetre-scale. Thermal drone and ground measurements demonstrated that N application leads to cooler leaf temperatures, which led to a strong relationship with ground-measured leaf stomatal conductance (R2 = 0.6; P < 0.01). Final grain yield was most accurately predicted by optical reflectance (MTCI, R2 = 0.94; P < 0.001). Precise retrieval of leaf-level crop performance indicators from drones establishes significant potential for optimising fertiliser application, to reduce environmental costs and improve yields.Competing Interest StatementThe authors have declared no competing interest.

Bait-delivered pharmaceuticals, increasingly used to manage populations of wild boar (Sus scrofa) and feral pigs, may be ingested by nontarget species. Species-specificity could be achieved through a delivery system. We designed the BOS™ (Boar-Operated-System) as a device to deliver baits to wild pigs. The BOS™ consists of a metal pole onto which a round perforated base is attached. A metal cone with a wide rim slides up and down the pole and fully encloses the base onto which the baits are placed. We conducted a pilot, captive trial and found that captive wild boar fed from the BOS™ either directly, by lifting the cone, or indirectly, by feeding once another animal had lifted the cone. Thus, we tested whether free-living wild boar fed from the BOS™ and whether the BOS™ could prevent bait uptake by nontarget species. We observed that free-living wild boar fed regularly from the BOS™ and that the device successfully prevented bait uptake by nontarget species. The BOS™ should be trialed more extensively to confirm its effectiveness and species-specificity to distribute pharmaceuticals to wild suids. If successful, the BOS™ could be used to deliver vaccines in disease control programs as well as contraceptives to manage overabundant populations of wild suids.

Arbuscular mycorrhizal fungi (AMF) can form a mutualistic symbiosis with over two-thirds of all land plants, providing phosphorus and/or nitrogen in exchange for carbon. They can have a significant effect on the surrounding soil, altering pH, water content, structure, and drainage. Important greenhouse gases (GHG) including carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) can be influenced by these factors, yet to date the interactions between AMF and soil GHG fluxes are surprisingly understudied. A microcosm system was developed to study GHG fluxes in the presence and absence of AMF hyphae. A central compartment contained an AMF host plant (Zea mays L.), with two outer compartments, that either allowed (AMA) or prevented (NAMA) AMF hyphal access. Organic matter patches of dried, milled, Z. mays leaves mixed with soil were added to the outer compartments to encourage proliferation of AMF hyphae and GHG production. Soil-atmosphere fluxes of N2O, CO2 and CH4 from the outer compartments were quantified, and gas probes were developed to measure N2O concentrations within the organic matter patches. Data from a series of microcosm experiments provide evidence for AMF interactions with soil fluxes of N2O and CO2, but not CH4. Soil CO2 fluxes were found to be a useful non-invasive method for determining the presence of AMF in hyphal compartments. The N2O concentrations in organic patches decreased in AMA treatments, and a subsequent experiment demonstrated that N2O production by nitrifiers may be limited in the presence of AMF hyphae. In contrast, following harvesting, N2O fluxes from organic matter patches were higher in the AMA treatment; possibly because carbon release from severed AMF hyphae fuelled denitrification. These interactions have important implications for N cycling and sustainable agriculture. The evidence presented in this thesis suggests that AMF may play a previously unappreciated role in reducing soil-atmosphere losses of N2O.

Graphical Abstract In this article we describe two predictive models that can be used for the integrated management of wheat bulb fly. Our first model is a pest level prediction model and our second model predicts the number of shoots a winter wheat crop will achieve by the terminal spikelet developmental stage. We revise and update current wheat bulb fly damage thresholds and combine this with our two models to devise a tolerance-based decision support system that can be used to minimise the risk of crop damage by wheat bulb fly. Figure1 Figure1 * Download figure * Open in new tab Summary Wheat bulb fly, Delia coarctata, is an important pest of winter wheat in the UK, causing significant damage of up to 4 t ha-1. Accepted population thresholds for D. coarctata are 250 eggs m-2 for crops sown up to the end of October and 100 eggs m-2 for crops sown from November. Fields with populations of D. coarctata that exceed the thresholds are at higher risk of experiencing economically damaging pest infestations. In the UK, recent withdrawal of insecticides means that only a seed treatment is available for chemical control of D. coarctata, however this is only effective for late-sown crops (November onwards) and accurate estimations of annual population levels are required to ensure a seed treatment is applied if needed. As a result of the lack of post-drilling control strategies, the management of D. coarctata is becoming increasingly reliant on non-chemical methods of control. Control strategies that are effective in managing similar stem-boring pests of wheat include sowing earlier and using higher seed rates to produce crops with more shoots and greater tolerance to shoot damage. In this study we develop two predictive models that can be used for integrated D. coarctata management. The first is an updated pest level prediction model that predicts D. coarctata populations from meteorological parameters with a predictive accuracy of 70%, which represents a significant improvement on the previous D. coarctata population prediction model. Our second model predicts the maximum number of shoots for a winter wheat crop that would be expected at the terminal spikelet development stage. This shoot number model uses information about the thermal time from plant emergence to terminal spikelet, leaf phyllochron length, plant population, and sowing date to predict the degree of tolerance a crop will have against D. coarctata. The shoot number model was calibrated against data collected from five field experiments and tested against data from four experiments. Model testing demonstrated that the shoot number model has a predictive accuracy of 70%. A decision support system using these two models for the sustainable management of D. coarcata risk is described. Competing Interest Statement The authors have declared no competing interest.

Horseshoe crabs, considered living fossils with a stable morphotype spanning ∼445 million years, are evolutionarily, ecologically, and biomedically important species experiencing rapid population decline. Of the four extant species of horseshoe crabs, the Atlantic horseshoe crab, Limulus polyphemus, has become an essential component of the modern medicine toolkit. Here, we present the first chromosome-level genome assembly, and the most contiguous and complete assembly to date, for L. polyphemus using nanopore long-read sequencing and chromatin conformation analysis. We find support for three horseshoe crab-specific whole-genome duplications, but none shared with Arachnopulmonata (spiders and scorpions). Moreover, we discovered tandem duplicates of endotoxin detection pathway components Factors C and G, identify candidate centromeres consisting of Gypsy retroelements, and classify the ZW sex chromosome system for this species and a sister taxon, Carcinoscorpius rotundicauda. Finally, we revealed this species has been experiencing a steep population decline over the last 5 million years, highlighting the need for international conservation interventions and fisheries-based management for this critical species.