Healthy soils are key to sustainability and food security. In temperate grasslands, not many studies have focused on soil health comparisons between contrasting pasture systems under different management strategies and treatment applications (e.g. manures and inorganic fertilisers). The aim of this study was to assess the responses of soil health indicators to dung, urine and inorganic N fertiliser in three temperate swards: permanent pasture not ploughed for at least 20 years (PP), high sugar ryegrass with white clover targeted at 30% coverage reseeded in 2013 (WC), and high sugar ryegrass reseeded in 2014 (HG). This study was conducted on the North Wyke Farm Platform (UK) from April 2017 to October 2017. Soil health indicators including soil organic carbon (SOC, measured by loss of ignition and elemental analyser), dissolved organic carbon (DOC), total nitrogen (TN), C:N ratio, soil C and N bulk isotopes, pH, bulk density (BD), aggregate stability, ergosterol concentration (as a proxy for fungi biomass), and earthworms (abundance, mass and density) were measured and analysed before and after application of dung and N fertilizer, urine and N fertiliser, and only N fertiliser. The highest SOC, TN, DOC, ergosterol concentration and earthworms as well as the lowest BD were found in PP, likely due to the lack of ploughing. Differences among treatments were observed due to the application of dung, resulting in an improvement in chemical indicators of soil health after 50 days of its application. Ergosterol concentration was significantly higher before treatment applications than at the end of the experiment. No changes were detected in BD and aggregate stability after treatment applications. We conclude that not enough time had passed for the soil to recover after the ploughing and reseeding of the permanent pasture, independently of the sward composition (HG or WC). Our results highlight the strong influence of the soil management legacy in temperate pasture and the positive effects of dung application on soil health over the short term. In addition, we point out the relevance of using standardised methods to report soil health indicators and some methodological limitations.
Background and aims The intake of selenium, an essential element for animals and humans, in ruminants is largely determined by selenium concentration in ingested forages, which take up selenium mainly from soil. Ruminant excreta is a common source of organic fertilizer, which provides both nutrients and organic matter. This study aims to unentangle the unclear effect of applying different types of ruminant excreta in soils of different organic matter contents on selenium uptake by forage. Methods Perennial ryegrass ( Lolium perenne ) was grown in soils of different organic matter contents. Urine and/or feces collected from sheep fed with organic or inorganic mineral supplements, including selenium, were applied to the soils. The selenium in the collected samples were analyzed using ICP-MS. The associated biogeochemical reactions were scrutinized by wet chemistry. Results The application of urine and/or feces resulted in either the same or lower selenium concentrations in perennial ryegrass. The excreta type did not affect total selenium accumulation in grass grown in low organic matter soil, whereas in high organic matter soil, feces resulted in significantly lower total selenium accumulation than urine, which was attributed to a possible interaction of selenium sorption in soil and microbial reduction of Se. Conclusion This one-time excreta application did not increase, but further decrease in some treatments, selenium concentration and accumulation in the perennial ryegrass. Consequently, to increase ruminant selenium intake, supplementing selenium directly to animals is more recommended than applying animal manure to soil, which might drive selenium reduction and decrease selenium uptake by grass.
Organic matter amendments appear to increase yield, but need to be sustained, as yield decreases when amendments cease. Here we mathematically devise optimal strategies for organic matter applications that take account of how quickly, in years of application, yields build up with amendments and how long these benefits persist. The empirical idea of a nutrient response curve is used and extended to include more than a single nutrient input as well as the effect of yield-enhancing factors such as organic matter that endure for more than one year. Nonlinear regression is used for the selection and the parameter identification for a reciprocal response curve working with a dataset from Rothamsted’s Woburn organic manuring long term experiment. Such a response curve is then treated analytically to develop economically optimum applications over a period of time. A simple static case is developed first and is shown to be equivalent to the well-known break-even ratio (BER) used in nitrogen fertiliser guidance by the Agricultural and Horticultural Development Board in the UK. The mathematical technique of optimal control is then employed to deduce dynamic strategies where the application of an amendment may change from year to year and for different time frames. Because this empirical modelling methodology can appear complex, we infer a rule-of-thumb for an equilibrium level of yield-enhancement rather like the equilibrium level of organic carbon that builds up over several years. This yield-enhancing power of organic matter is somewhat variable and probably does not persist in soil for as long as the organic matter from which it derives. It appears beneficial to apply amendments at a constant rate for much of the time-frame of interest but to begin with a large application to raise the fertility to the yield-enhancement equilibrium. After a transition year with reduced amendments, applications of organic matter are stopped for the final five years with the example amendment studied, farmyard manure. These conclusions depend on the persistence of the yield-enhancing power of organic matter in soil associated with the soil organic carbon kinetics.
There is a growing recognition of the challenges associated with ensuring good nutrition for all without compromising the environment. This is particularly true for aquaculture, given the reliance on marine extraction for key feed ingredients, yet at the same time it delivers key nutrients such as omega-3 long chain polyunsaturated fatty acids. This review will consider progress in transitioning away from oceanic-derived fish oils as feed ingredients, focusing on the emerging transgenic plant sources of these fatty acids. Specific consideration is given to the “validation” phase of this process, in which oils from GM plants are used as substitutes for bona fide fish oils in aquafeed diets. Equally, consideration is given to the demonstration of “real-world” potential by GM field trials. Collectively, the status of these new plant-based sources of omega-3 fish oils confirm the arrival of a new wave of plant biotech products, 25 years after the introduction of herbicide-tolerant input traits and demonstrate the power of GM agriculture to contribute to food security and operating within planetary boundaries.
While mechanisms of plant–plant communication for alerting neighbouring plants of an imminent insect herbivore attack have been described aboveground via the production of volatile organic compounds (VOCs), we are yet to decipher the specific components of plant–plant signalling belowground. Using bioassay‐guided fractionation, we isolated and identified the non‐protein amino acid l‐DOPA, released from roots of Acyrtosiphon pisum aphid‐infested Vicia faba plants, as an active compound in triggering the production of VOCs released aboveground in uninfested plants. In behavioural assays, we show that after contact with l‐DOPA, healthy plants become highly attractive to the aphid parasitoid (Aphidius ervi), as if they were infested by aphids. We conclude that l‐DOPA, originally described as a brain neurotransmitter precursor, can also enhance immunity in plants.
Very-long-chain fatty acids (VLCFA) are precursors for various lipids playing important physiological and structural roles in plants. Throughout plant tissues, VLCFA are present in multiple lipid classes essential for membrane homeostasis, and also stored in triacylglycerols. VLCFA and their derivatives are also highly abundant in lipid barriers, such as cuticular waxes in aerial epidermal cells and suberin monomers in roots. VLCFA are produced by the fatty acid elongase (FAE), which is an integral endoplasmic reticulum membrane multi-enzymatic complex consisting of four core enzymes. The 3-ketoacyl-CoA synthase (KCS) catalyzes the first reaction of the elongation and determines the chain-length substrate specificity of each elongation cycle, whereas the other three enzymes have broad substrate specificities and are shared by all FAE complexes. Consistent with the co-existence of multiple FAE complexes, performing sequential and/or parallel reactions to produce the broad chain-length-range of VLCFA found in plants, twenty-one KCS genes have been identified in the genome of Arabidopsis thaliana . Using CRISPR-Cas9 technology, we established an expression platform to reconstitute the different Arabidopsis FAE complexes in yeast. The VLCFA produced in these yeast strains were analyzed in detail to characterize the substrate specificity of all KCS candidates. Additionally, Arabidopsis candidate proteins were transiently expressed in Nicotiana benthamiana leaves to explore their activity and localization in planta . This work sheds light on the genetic and biochemical redundancy of fatty acid elongation in plants.
Plants respond indirectly to herbivore injury in a species‐specific way and emit a specific blend of volatiles that are attractive to the enemies of herbivores. We evaluated whether maize plants, Zea mays L. (Poaceae), can recognize herbivory damage from a generalist stink bug, Diceraeus (Dichelops) melacanthus Dallas (Hemiptera: Pentatomidae). This species is not a common pest in maize, but is currently found on maize crops in Brazil. We aimed to answer the following questions: (1) does D. melacanthus use maize plant volatiles for host location? (2) Do maize plant chemical volatile profiles change due to feeding by D. melacanthus? And (3) do herbivore‐induced plant volatiles (HIPVs) emitted by maize plants play a role in the foraging behaviour of the generalist stink bug egg parasitoid Telenomus podisi Ashmead (Hymenoptera: Platygastridae)? The results show that females of D. melacanthus do not use constitutive volatiles or HIPVs as host location cues. However, feeding by D. melacanthus activates maize indirect defence, inducing emission of HIPVs and attracting the herbivore's enemy. Thus, strengthening indirect defence of plants can be a strategy to protect crops in the field by recruiting natural enemies through chemical information, as an additional approach to control D. melacanthus within an integrated pest management program.
Advances in biocontrol potentials and fungicide resistance are highly desirable for Trichoderma. Thus, it is profitable to use mutagenic agents to develop superior strains with enhanced biocontrol properties and fungicide tolerance in Trichoderma. This study investigates the N-methyl-n-nitro-N-nitrosoguanidine (NTG) (100 mg/L) induced mutants of Trichoderma asperellum. Six NTG (3 each from 1st & 2nd round) induced mutants were developed and evaluated their biocontrol activities and carbendazim tolerance. Among the mutant N2-3, N2-1, N1 and N2-2 gave the best antagonistic and volatile metabolite activities on inhibition of chickpea F. oxysporum f. sp. ciceri, B. cinerea and R. bataticola mycelium under in vitro condition. Mutant N2-2 (5626.40 μg/ml) showed the highest EC50 value against carbendazim followed by N2-3 (206.36 μg/ml) and N2-1 (16.41 μg/ml); and succeeded to sporulate even at 2000 μg/ml of carbendazim. The biocontrol activity of N2-2 and N2 with half-dose of carbendazim was evaluated on chickpea dry root rot under controlled environment. Disease reduction and progress of the dry root rot was extremely low in T7 (N2-2 + with half-dose of carbendazim) treatment. Further, carbendazim resistant mutants demonstrated mutation in tub2 gene of β-tubulin family which was suggested through the 37 and 183 residue changes in the superimposed protein structures encoded by tub2 gene in N2 and N2-2 with WT respectively. This study conclusively implies that the enhanced carbendazim tolerance in N2-2 mutant did not affect the mycoparasitism and plant growth activity of Trichoderma. These mutants were as good as the wild-type with respect to all inherent attributes.
Strigolactones (SLs) are a class of phytohormones regulating branching/tillering and their biosynthesis has been associated with nutritional signals and plant adaptation to nutrient-limiting conditions. The enzymes in the SL biosynthetic pathway downstream of carlactone are of interest as they are responsible for structural diversity in SLs, particularly cytochrome P450 CYP711A subfamily members, such as MORE AXILLARY GROWTH1 (MAX1) in Arabidopsis. We identified 13 MAX1 homologues in wheat, clustering in four clades and five homoeologous subgroups. The utilization of RNA-sequencing data revealed a distinct expression pattern of MAX1 homologues in above- and below-ground tissues, providing insights into the distinct roles of MAX1 homologues in wheat. In addition, a transcriptional analysis showed that SL biosynthetic genes were systematically regulated by nitrogen supply. Nitrogen limitation led to larger transcriptional changes in the basal nodes than phosphorus limitation, which was consistent with the observed tillering suppression, as wheat showed higher sensitivity to nitrogen. The opposite was observed in roots, with phosphorus limitation leading to stronger induction of most SL biosynthetic genes compared to nitrogen limitation. The observed tissue-specific regulation of SL biosynthetic genes in response to nutritional signals is likely to reflect the dual role of SLs as rhizosphere signals and branching inhibitors.
Introduction Septoria tritici blotch (STB) is one of the most damaging fungal diseases of wheat in Europe, largely due to the paucity of effective resistance genes against it in breeding materials. Currently dominant protection methods against this disease, e.g. fungicides and the disease resistance genes already deployed, are losing their effectiveness. Therefore, it is vital that other available disease resistance sources are identified, understood and deployed in a manner that maximises their effectiveness and durability. Methods In this study, we assessed wheat genotypes containing nineteen known major STB resistance genes (Stb1 through to Stb19 ) or combinations thereof against a broad panel of 93 UK Zymoseptoria tritici isolates. Seedlings were inoculated using a cotton swab and monitored for four weeks. Four infection-related phenotypic traits were visually assessed. These were the days post infection to the development of first symptoms and pycnidia, percentage coverage of the infected leaf area with chlorosis/necrosis and percentage coverage of the infected leaf area with pycnidia. Results The different Stb genes were found to vary greatly in the levels of protection they provided, with pycnidia coverage at four weeks differing significantly from susceptible controls for every tested genotype. Stb10 , Stb11 , Stb12 , Stb16q , Stb17 , and Stb19 were identified as contributing broad spectrum disease resistance, and synthetic hexaploid wheat lines were identified as particularly promising sources of broadly effective STB resistances. Discussion No single Z. tritici isolate was found to be virulent against all tested resistance genes. Wheat genotypes carrying multiple Stb genes were found to provide higher levels of resistance than expected given their historical levels of use. Furthermore, it was noted that disease resistance controlled by different Stb genes was associated with different levels of chlorosis, with high levels of early chlorosis in some genotypes correlated with high resistance to fungal pycnidia development, potentially suggesting the presence of multiple resistance mechanisms. The knowledge obtained here will aid UK breeders in prioritising Stb genes for future breeding programmes, in which optimal combinations of resistance genes could be pyramided. In addition, this study identified the most interesting Stb genes for cloning and detailed functional analysis.
Amaranthus retroflexus L. and Chenopodium album L. (Amaranthaceae) are weedy plants that cause severe ecological and economic damage. In this study, we collected DNA from three different countries and assessed genetic diversity using inter-simple sequence repeat (ISSR) markers. Our analysis shows both weed species have low genetic diversity within a population and high genetic diversity among populations, as well as a low value of gene flow among the populations. UPGMA clustering and principal coordinate analysis indicate four distinct groups for A. retroflexus L. and C. album L. exist. We detected significant isolation-by-distance for A. retroflexus L. and no significant correlation for C. album L. These conclusions are based data from 13 ISSR primers where the average percentage of polymorphism produced was 98.46% for A. retroflexus L. and 74.81% for C. album L.These data suggest that each population was independently introduced to the location from which it was sampled and these noxious weeds come armed with considerable genetic variability giving them the opportunity to manifest myriad traits that could be used to avoid management practices. Our results, albeit not definitive about this issue, do not support the native status of C. album L. in Iran.
The rapid increase of herbicide resistance in some of the most problematic annual weeds, and potential negative impacts of herbicides on human health and the environment have led growers to look for alternative non-chemical weed control. Harvest weed seed control (HWSC) is a non-chemical weed control tactic based on reduction of seed return of primarily annual weed species to the soil seed bank that has been successfully adopted by farmers in Australia. The strategy is to collect and/or destroy the weed seeds in the chaff material during harvest using chaff carts, bale direct system, integrated impact mills, windrow burning, chaff tramlining and chaff lining or other methods of targeting the chaff material containing the weed seeds. Two biological characteristics are exploited with successful HWSC: the level of weed seed retention at crop harvest above crop canopy height and coincidence of weed and crop maturity. Initial research efforts in Europe have found that there are several candidates for HWSC among weed species with a high importance in European cropping systems. The highest potential has been found for weeds such as Galium aparine, Lolium rigidum and Silene noctiflora. However, there are several challenges for the adoption of these systems under European conditions compared to e.g., Australia. The challenges include that crop and weed maturity are not concomitant which results in lower seed retention values at crop harvest. In addition, there has not been a concerted research effort to evaluate HWSC systems in European cropping systems. Until now, research on HWSC in Europe mainly focused on the rate of weed seed retention in specific weed species. For HWSC to contribute to the mitigation of herbicide resistance and add to the toolbox of integrated weed management measures, there is an urgent need to take HWSC research to the next level. Although HWSC is not functionally equivalent to herbicide application, it may help to reduce herbicide inputs in the long-term when used in combination with other tactics. Future research and development should focus on the evaluation of HWSC strategies for the practical adoption of these tactics in European cropping systems.
Blackleg (Phoma) disease, caused by the ascomycete fungi Plenodomus biglobosus and P. lingam, threatens oilseed rape (OSR; Brassica napus) crops internationally. In many parts of the world, both species co‐occur, but in China only P. biglobosus has so far been reported. Plenodomus biglobosus reproduces asexually (pycnidiospores), but also sexually (pseudothecia‐yielding asco‐ spores), via a heterothallic mating system requiring MAT1‐1 and MAT1‐2 genotypes. However, the roles of airborne ascospore inoculum in driving blackleg disease outbreaks in China are less well understood compared to elsewhere in the world. This is despite the very different agronomic crop‐ ping practices in parts of China, in which paddy rice and OSR are often grown in rotation; OSR stubble is often submerged under water for long periods potentially affecting pseudothecial devel‐ opment. Here, we indirectly investigate the potential role of sexual reproduction by developing new polymerase chain reaction (PCR) ‐based mating‐type diagnostics for P. biglobosus and subsequently screening an international collection of 59 European and 157 Chinese isolates. Overall, in both Eu‐ rope and China, P. biglobosus mating types did not deviate from a 1:1 ratio, such as is generally thought to occur under frequency‐dependent selection in sexually reproducing pathogen popula‐ tions. Both mating types were balanced in all the individual European countries tested (Austria, France, Poland, UK). Conversely, in China, mating types were only balanced in the eastern region; in the northern and southwestern regions there were skewed ratios, more typical of predominantly asexual reproduction, towards MAT1‐1 and MAT1‐2, respectively. The implications of these find‐ ings and future research directions for improved understanding of P. biglobosus epidemiology on OSR, particularly in China, are considered.
Background: The cabbage stem flea beetle (CSFB; Psylliodes chrysocephala) is an important pest of winter oilseed rape (OSR) crops in Europe. Damage is caused by adults feeding on young leaves and by larvae mining in the leaves and stems. The most common method to estimate the severity of CSFB larval infestation is by plant dissection, which is time consuming and labour intensive. Two alternative methods have been proposed; extraction of larvae from desiccating plants and counting the percentage of leaves with scars left by larvae on plant petioles. These methods are easy to implement and less time consuming than plant dissection but have not been properly validated. Results: OSR plants were sampled in five different experiments and the two alternative methods tested; assessment of the total number of scars per plant as a predictor of the number of larvae was also tested. The number of larvae remaining in plants following various periods of desiccation was checked via plant dissection. We found that the desiccation method is efficient, giving reliable results after 7 days (76 % of the total larvae extracted) with good accuracy in estimating the number of larvae per plant (± 0.38 larvae per plant). The total number of scars also gives a reliable estimation of the number of larvae (r = 0.76, accuracy of ± 1.01 larvae per plant). Conclusion: OSR plant desiccation and the total number of scars per plant are reliable methods to estimate CSFB larval infestation and will facilitate monitoring of this cryptic pest stage. This article is protected by copyright. All rights reserved.
Achieving food security requires resilient agricultural systems with improved nutrient-use efficiency, optimized water and nutrient storage in soils, and reduced gaseous emissions. Success relies on understanding coupled nitrogen and carbon metabolism in soils, their associated influences on soil structure and the processes controlling nitrogen transformations at scales relevant to microbial activity. Here we show that the influence of organic matter on arable soil nitrogen transformations can be decoded by integrating metagenomic data with soil structural parameters. Our approach provides a mechanistic explanation of why organic matter is effective in reducing nitrous oxide losses while supporting system resilience. The relationship between organic carbon, soil-connected porosity and flow rates at scales relevant to microbes suggests that important increases in nutrient-use efficiency could be achieved at lower organic carbon stocks than currently envisaged. This study uses arable soils subjected to consistent management for over 160 years to understand the influence of organic matter on arable soil nitrogen metabolism. The nonlinear and systems-level approach shows that important increases in nutrient-use efficiency can be achieved to improve soil organic carbon stocks and reduce N2O emissions.
Channel banks can contribute a significant proportion of fine‐grained (<63 μm) sediment to rivers, thereby also contributing to riverine total particulate phosphorus loads. Improving water quality through better agricultural practices alone can be difficult since the contributions from non‐agricultural sources, including channel banks, can generate a ‘spatial mismatch’ between the efficacy of best management applied on farms and the likelihood of meeting environmental objectives. Our study undertook a reconnaissance survey (n=76 sites each with 3 profiles sampled) to determine the total phosphorus (TP) concentrations of channel banks across England and to determine if TP content can be predicted using readily accessible secondary data. TP concentrations in adjacent field topsoils, local soil soil type/texture and geological parent material were examined as potential predictors of bank TP. Carbon and nitrogen content were also analysed to explore the impacts of organic matter content on measured TP concentrations. The results suggest that channel bank TP concentrations are primarily controlled by parent material rather than P additions to adjacent topsoils through fertiliser and organic matter inputs, but significant local variability in concentrations prevents the prediction of bank TP content using mapped soil type or geology. A median TP concentration of 873 mg kg‐1 was calculated for the middle section of the sampled channel bank profiles, with a 25th percentile of 675 mg kg‐1, and 75th percentile of 1159 mg kg‐1. Using these concentrations and, in comparison with previously published estimates, the estimated number of inland WFD waterbodies in England for which channel bank erosion contributes >20% of the riverine total PP load increased from 15 to 25 (corresponding range of 17 to 35 using the 25th and 75th percentiles of measured TP concentrations). Collectively, these 25 waterbodies account for 0.2% of the total inland WFD waterbody area comprising England. This article is protected by copyright. All rights reserved.
Wheat is the most widely grown food crop, with 761 Mt produced globally in 2020. To meet the expected grain demand by mid-century, wheat breeding strategies must continue to improve upon yield-advancing physiological traits, regardless of climate change impacts. Here, the best performing doubled haploid (DH) crosses with an increased canopy photosynthesis from wheat field experiments in the literature were extrapolated to the global scale with a multi-model ensemble of process-based wheat crop models to estimate global wheat production. The DH field experiments were also used to determine a quantitative relationship between wheat production and solar radiation to estimate genetic yield potential. The multi-model ensemble projected a global annual wheat production of 1,050 ± 145 Mt due to the improved canopy photosynthesis, a 37% increase, without expanding cropping area. Achieving this genetic yield potential would meet the lower estimate of the projected grain demand in 2050, albeit with considerable challenges.
1. Generalist invertebrate predators are sensitive to weather conditions, but the relationship between their trophic interactions and weather is poorly understood. This study investigates how weather affects the identity and frequency of spider trophic interactions as mediated by prey community structure, web characteristics and density-independent prey choice. 2. Spiders and their locally available prey were collected from barley fields in Wales, UK from April to September 2017-2018. The gut contents of 300 spiders were screened using DNA metabarcoding, analysed via multivariate models, and compared against prey availability using null models. 3. Spiders’ trophic interactions changed over time and with weather conditions, primarily related to concomitant changes in their prey communities. Spiders did, however, appear to mitigate the effects of structural changes in prey communities through changing prey preferences according to prevailing weather conditions, possibly facilitated by adaptive web construction. 4. Using these findings, we demonstrate that prey choice data collected under different weather conditions can be used to refine inter-annual predictions of spider trophic interactions, although prey abundance was secondary to diversity in driving the diet of these spiders. By improving our understanding of the interaction between trophic interactions and weather, we can better predict how ecological networks are likely to change in response to variation in weather conditions and, more urgently, global climate change.
The growing world population and global increases in the standard of living both result in an increasing demand for food, feed and other plant‐derived products. In the coming years, plant‐based research will be among the major drivers ensuring food security and the expansion of the bio‐based economy. Crop productivity is determined by several factors, including the available physical and agricultural resources, crop management, and the resource use efficiency, quality and intrinsic yield potential of the chosen crop. This review focuses on intrinsic yield potential, since understanding its determinants and their biological basis will allow to maximize the plant's potential in food and energy production. Yield potential is determined by a variety of complex traits that integrate strictly regulated processes and their underlying gene regulatory networks. Due to this inherent complexity, numerous potential targets have been identified that could be exploited to increase crop yield. These encompass diverse metabolic and physical processes at the cellular, organ and canopy level. We present an overview of some of the distinct biological processes considered to be crucial for yield determination that could further be exploited to improve future crop productivity. The manuscript is part of a review collection from the CropBooster‐P project (https://www.cropbooster‐p.eu/). In this review, we present an overview of some of the distinct biological processes considered to be crucial for yield determination and recent updates in the respective fields. In the future, these could further be exploited to improve crop productivity.
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