Showing papers by "Adrian C. Newton published in 2021"

Global challenges facing plant pathology: multidisciplinary approaches to meet the food security and environmental challenges in the mid-twenty-first century

Abstract: The discipline of plant pathology has an expanding remit requiring a multi-faceted, interdisciplinary approach to capture the complexity of interactions for any given disease, disease complex or syndrome. This review discussed recent developments in plant pathology research and identifies some key issues that, we anticipate, must be faced to meet the food security and environmental challenges that will arise over coming decades. In meeting these issues, the challenge in turn is for the plant pathology community to respond by contributing to a wider forum for multidisciplinary research, recognising that impact will depend not just on advances in the plant pathology discipline alone, but on interactions more broadly with other agricultural and ecological sciences, and with the needs of national and global policies and regulation. A challenge more readily met once plant pathologists again gather physically at international meetings and return to the professional and social encounters that are fertile grounds for developing new ideas and forging collaborative approaches both within plant pathology and with other disciplines. In this review we emphasise, in particular: the multidisciplinary links between plant pathology and other disciplines; disease management, including precision agriculture, plant growth and development, and decision analysis and disease risk; the development and use of new and novel plant protection chemicals; new ways of exploiting host genetic diversity including host resistance deployment; a new perspective on biological control and microbial interactions; advances in surveillance and detection technologies; invasion of exotic and re-emerging plant pathogens; and the consequences of climate change affecting all aspects of agriculture, the environment, and their interactions. We draw conclusions in each of these areas, but in reaching forward over the next few decades, these inevitably lead to further research questions rather than solutions to the challenges we anticipate.

Chitosan primes plant defence mechanisms against Botrytis cinerea, including expression of Avr9/Cf-9 rapidly elicited genes

Abstract: Current crop protection strategies against the fungal pathogen Botrytis cinerea rely on a combination of conventional fungicides and host genetic resistance. However, due to pathogen evolution and legislation in the use of fungicides, these strategies are not sufficient to protect plants against this pathogen. Defence elicitors can stimulate plant defence mechanisms through a phenomenon known as defence priming. Priming results in a faster and/or stronger expression of resistance upon pathogen recognition by the host. This work aims to study defence priming by a commercial formulation of the elicitor chitosan. Treatments with chitosan result in induced resistance (IR) in solanaceous and brassicaceous plants. In tomato plants, enhanced resistance has been linked with priming of callose deposition and accumulation of the plant hormone jasmonic acid (JA). Large-scale transcriptomic analysis revealed that chitosan primes gene expression at early time-points after infection. In addition, two novel tomato genes with a characteristic priming profile were identified, Avr9/Cf-9 rapidly elicited protein 75 (ACRE75) and 180 (ACRE180). Transient and stable over-expression of ACRE75, ACRE180 and their Nicotiana benthamiana homologs, revealed that they are positive regulators of plant resistance against B. cinerea. This provides valuable information in the search for strategies to protect Solanaceae plants against B. cinerea.

The rise, fall and resurrection of chemical induced resistance agents.

Abstract: Since the discovery that the plant immune system could be augmented for improved deployment against biotic stressors through the exogenous application of chemicals that lead to induced resistance (IR), many such IR-eliciting agents have been identified. Initially it was hoped that these chemical IR agents would be a benign alternative to traditional chemical biocides. However, owing to low efficacy and/or a realization that their benefits sometimes come at the cost of growth and yield penalties, chemical IR agents fell out of favour and were seldom used as crop protection products. Despite the lack of interest in agricultural use, researchers have continued to explore the efficacy and mechanisms of chemical IR. Moreover, as we move away from the approach of 'zero tolerance' toward plant pests and pathogens toward integrated pest management, chemical IR agents could have a place in the plant protection product list. In this review, we chart the rise and fall of chemical IR agents, and then explore a variety of strategies used to improve their efficacy and remediate their negative adverse effects. © 2021 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Grain Yield Stability of Cereal-Legume Intercrops Is Greater Than Sole Crops in More Productive Conditions

Abstract: The intercropping of two or more crop species on the same piece of land at a given time has been hypothesized to enhance crop yield stability. To address this hypothesis, we assessed the grain yield stability of various barley-pea and wheat-faba bean mixtures grown in seven experimental field trials (locations) across Europe during two years with contrasting weather (2017 and 2018). Three different yield stability measures were used, all based on the expected yield variability of the mixture components grown as sole crops, and the corresponding observed yield variability of the same components grown in 50:50 mixtures in a replacement design. Stability indices were calculated as ratios between the expected and observed variabilities, with values > 1 indicating greater stability of the intercrops. Mean grain yields tended to be higher in intercrops than sole crops. However, in contrast to our hypothesis, the observed (intercrop) yield stability was similar or lower than the expected (sole crop) stability in most locations except one. Furthermore, yield stability significantly increased with increasing mean yields when assessed across differentially productive locations. The results are relevant for the designing of intercropping systems as a means to increase yield stability and the resilience of cropping systems.

Ecological restoration of agricultural land can improve its contribution to economic development.

Abstract: Given the negative environmental impacts of intensive agriculture, there is an urgent need to reduce the impact of food production on biodiversity. Ecological restoration of farmland could potentially contribute to this goal. While the positive impacts of ecological restoration on biodiversity are well established, less evidence is available regarding impacts on economic development and employment. Potentially, prospects for economic development could be enhanced by ecological restoration though increased provision of ecosystem services, on which some economic activity depends. Here we examined this issue through the development of contrasting land use scenarios for the county of Dorset, southern England. Two scenarios of future agricultural expansion were compared with two scenarios of landscape-scale ecological restoration and the current situation. Impacts on provision of multiple ecosystem services (ES) were explored using InVEST models and proxy values for different land cover types. Impacts on economic employment were examined using an economic input-output model, which was adjusted for variation in ES flows using empirically determined ES dependency values for different economic sectors. Using the unadjusted input-output model, the scenarios had only a slight economic impact (≤ 0.3% Gross Value Added, GVA). Conversely, when the input-output model was adjusted to take account of ES flows, GVA increased by up to 5.4% in the restoration scenarios, whereas under the scenario with greatest agricultural expansion, GVA was reduced by -4.5%. Similarly, employment increased by up to 6.7% following restoration, compared to declines of up to -5.6% following maximum agricultural expansion. These results show that the economic contribution of rural land is far greater than that attributable to agricultural production alone. Landscape-scale restoration of agricultural land can potentially increase the contribution of farmland to economic development and employment, by increasing flows of multiple ES to the many economic sectors that depend on them.

UK food and nutrition security during and after the COVID‐19 pandemic

Abstract: The COVID-19 pandemic is a major shock to society in terms of health and economy that is affecting both UK and global food and nutrition security. It is adding to the 'perfect storm' of threats to society from climate change, biodiversity loss and ecosystem degradation, at a time of considerable change, rising nationalism and breakdown in international collaboration. In the UK, the situation is further complicated due to Brexit. The UK COVID-19 F ood and N utrition S ecurity project, lasting one year, is funded by the Economic and Social Research Council and is assessing the ongoing impact of COVID-19 on the four pillars of food and nutrition security: access, availability, utilisation and stability. It examines the food system, how it is responding, and potential knock on effects on the UK's food and nutrition security, both in terms of the cascading risks from the pandemic and other threats. The study provides an opportunity to place the initial lessons being learnt from the on-going responses to the pandemic in respect of food and nutrition security in the context of other long-term challenges such as climate change and biodiversity loss.

Inconsistent detection of extinction debts using different methods

Abstract: © 2020 The Authors. Ecography published by John Wiley & Sons Ltd on behalf of Nordic Society Oikos The extinction debt, delayed species extinctions following landscape degradation, is a widely discussed concept. But a consensus about the prevalence of extinctions debts is hindered by a multiplicity of methods and a lack of comparisons among habitats. We applied three contrasting species–area relationship methods to test for plant community extinction debts in three habitats which had different degradation histories over the last century: calcareous grassland, heathland and woodland. These methods differ in their data requirements, with the first two using information on past and current habitat area alongside current species richness, whilst the last method also requires data on past species richness. The most data-intensive, and hence arguably most reliable method, identified extinction debts across all habitats for specialist species, whilst the other methods did not. All methods detected an extinction debt in calcareous grassland, which had undergone the most severe degradation. We conclude that some methods failed to detect an extinction debt, particularly in habitats that have undergone moderate degradation. Data on past species numbers are required for the most reliable method; as such data are rare, extinction debts may be under-reported.

Ecosystem Collapse and Recovery

Abstract: There is a growing concern that many important ecosystems, such as coral reefs and tropical rain forests, might be at risk of sudden collapse as a result of human disturbance At the same time, efforts to support the recovery of degraded ecosystems are increasing, through approaches such as ecological restoration and rewilding Given the dependence of human livelihoods on the multiple benefits provided by ecosystems, there is an urgent need to understand the situations under which ecosystem collapse can occur, and how ecosystem recovery can best be supported To help develop this understanding, this volume provides the first scientific account of the ecological mechanisms associated with the collapse of ecosystems and their subsequent recovery After providing an overview of relevant theory, the text evaluates these ideas in the light of available empirical evidence, by profiling case studies drawn from both contemporary and prehistoric ecosystems Implications for conservation policy and practice are then examined

Variable impacts of reduced and zero tillage on soil carbon storage across 4–10 years of UK field experiments

Abstract: Reduced tillage has been advocated as a practical measure to increase soil carbon in long-term cropping soils. We examine three medium-term experiments in sites with contrasting soil and climatic characteristics in the UK. The objectives were to determine the effects of different reduced and zero tillage practices on bulk density and soil carbon storage and depth distribution and to quantify the effect of stones in their calculation. The treatments were zero tillage, minimum tillage, conventional plough, deep non-inversion tillage and plough compaction. Soil samples were collected from three sites at five depth intervals to approximately 60 cm. Deep non-inversion and minimum tillage led to 6.5 and 1.6 Mg ha−1 greater SOC than conventional plough in sites under rotation systems. In a monoculture system in Scotland, conventional plough had 25.3, 21.6 and 17.7 Mg ha−1 greater SOC than plough compaction, minimum tillage and zero tillage, respectively. After harvest, bulk density was greater in the soil surface of conventional plough compared with minimum tillage. Our results suggest variable impacts of reduced tillage on SOC storage. Overall there is limited benefit in using shallow minimum tillage and zero tillage practices in the UK to increase soil carbon storage when a soil profile of 60 cm is considered but other benefits associated to these systems, such as speed of working and timeliness of operations, should be considered.

Does agricultural intensification cause tipping points in ecosystem services

Abstract: Agricultural intensification is being widely pursued as a policy option to improve food security and human development. Yet, there is a need to understand the impact of agricultural intensification on the provision of multiple ecosystem services, and to evaluate the possible occurrence of tipping points. We used the InVEST suite of software models together with a time series of historical land cover maps and an Input–Output model to evaluate these dynamics over an 85-year period in the county of Dorset, southern England. Results indicated that trends in ES were often non-linear, highlighting the potential for abrupt changes in ES provision to occur in response to slight changes in underlying drivers. Despite the fluctuations in provision of different ES, overall economic activity increased almost linearly during the study interval, in line with the increase in agricultural productivity. Such non-linear thresholds in ES will need to be avoided in the future by approaches aiming to deliver sustainable agricultural intensification. A number of positive feedback mechanisms are identified that suggest these thresholds could be considered as tipping points. However, further research into these feedbacks is required to fully determine the occurrence of tipping points in agricultural systems.

Challenging the Status Quo through Social Influence: Changes in Sustainable Consumption through the Influence of Social Networks

Abstract: This study examines the influence of social network members (versus strangers) on sustainable food consumption choices to investigate how social influence can challenge the status quo in unsustainable consumption practices. We hypothesized that changes to individual consumption practices could be achieved by revealing ‘invisible’ descriptive and injunctive social norms. We further hypothesized that it matters who reveals these norms, meaning that social network members expressing their norms will have a stronger influence on other’s consumption choices than if these norms are expressed by strangers. We tested these hypotheses in a field experiment (N = 134), where participants discussed previous sustainable food consumption (revealing descriptive norms) and its importance (revealing injunctive norms) with either a stranger or social network member. We measured actual sustainable food consumption through the extent to which participants chose organic over non-organic consumables during the debrief. Findings showed that revealed injunctive norms significantly influenced food consumption, more so than revealed descriptive norms. We also found that this influence was stronger for social network members compared to strangers. Implications and further research directions in relation to how social networks can be used to evoke sustainable social change are discussed.

Identifying potential novel resistance to the foliar disease ‘Scald’ (Rhynchosporium commune) in a population of Scottish Bere barley landrace (Hordeum vulgare L.)

Abstract: Barley ‘Scald’ is an economically damaging fungal disease that is a global problem, causing significant yield and economical losses in the UK barley feed and malting industries. Presently, a limited number of Rhynchosporium resistance genes exist, but selective pressures on the fungi cause the demand for new sources of resistance. Landraces, such as the Scottish Bere barley, hold potential sources of resistance that can be utilised, with farmers providing anecdotal evidence of resistance in field populations of Bere. This study analysed 131 heritage cultivars and landrace lines, including 37 Bere lines, to screen for resistance using both detached leaf assays (DLAs) and field experiments. Results showed that Bere lines produced smaller, but more necrotic, lesions for the majority of isolates in the DLAs, as well as smaller scores when visually assessed in field conditions. Whilst the infection patterns of the lines differed between isolates and experimental conditions, three Bere lines were identified as consistently showing reduced levels of infection (45 A 23, 58 A 36 Eday, and 8-125). Using genome-wide association analysis, we were able to identify a number of genomic regions associated with reduced infection symptoms, four in regions associated with known resistance genes, but another four associated with new regions that contain promising candidate genes. Further analysis of these new regions and candidate genes should be undertaken to identify targets for future disease-resistance breeding.

Using seed respiration as a tool for calculating optimal soaking times for 'on-farm' seed priming of barley (Hordeum vulgare)

Abstract: A low-cost technique named ‘on-farm’ seed priming is increasingly being recognized as an effective approach to maximize crop establishment. It consists of anaerobically soaking seeds in water before sowing resulting in rapid and uniform germination, and enhanced seedling vigour. The extent of these benefits depends on the soaking time. The current determination of optimal soaking time by germination assays and mini-plot trials is resource-intensive, as it is species/genotype-specific. This study aimed to determine the potential of the seed respiration rate (an indicator of metabolic activity) and seed morphological changes during barley priming as predictors of the priming benefits and, thus, facilitate the determination of optimal soaking times. A series of germination tests revealed that the germination rate is mostly attributable to the rapid hydration of embryo tissues, as the highest gains in the germination rate occurred before the resumption of respiration. Germination uniformity, however, was not significantly improved until seeds were primed for at least 8 h, that is, after a first respiration burst was initiated. The maximum seedling vigour was attained when the priming was stopped just before the beginning of the differentiation of embryonic axes (20 h) after which vigour began to decrease (‘over-priming’). The onset of embryonic axis elongation was preceded by a second respiration burst, which can be used as a marker for priming optimization. Thus, monitoring of seed respiration provides a rapid and inexpensive alternative to the current practice. The method could be carried out by agricultural institutions to provide recommended optimal soaking times for the common barley varieties within a specific region.

Can 'On-Farm' Seed Priming and Chitosan Seed Treatments Induce Host Defences in Winter Barley (Hordeum vulgare L.) under Field Conditions?

Abstract: Enhancing host defences through induced resistance, disease tolerance, and/or escape, in combination with current disease management regimes may be a valuable strategy to reduce pesticide use. Since both ‘on-farm’ seed priming (OSP) and chitosan priming (CHP) have been reported to confer varying levels of host defence, this study sought to investigate their potential to deliver disease control as a strategy for sustainable management of foliar pathogens in winter barley. Field experiments were conducted to determine the effects of OSP and CHP at two different field sites using three different cultivars under fungicide/non-fungicide regimes. Overall, no evidence was found to suggest that CHP or OSP can induce effective resistance in temperate field conditions. However, these field trials enabled the identification of candidate traits to deliver disease tolerance (and escape) for the primary and secondary spread of powdery mildew, i.e., large canopies and rapid stem elongation respectively. Thus, these seed treatments may deliver disease tolerance and escape traits, but these benefits are dependent upon successful establishment and vigour first. The integration of seed treatments into sustainable crop protection may be better undertaken with spring crops or in semi-arid agriculture where the added vigour at emergence can help compensate for negative environmental interactions.

Strengthening the Scientific Basis of Ecosystem Collapse Risk Assessments

Abstract: Progress is being made in assessing the conservation status of ecosystems, notably through initiatives such as the IUCN Red List of Ecosystems (RLE) and the NatureServe Conservation Status Assessment (NCS). Both of these approaches consider conservation status in terms of the risk of ecosystem collapse. However, the scientific understanding of ecosystem collapse is still at a relatively early stage. Consequently, concerns have been raised regarding the scientific basis of ecosystem conservation assessments focusing on collapse risk. Here I explore how these concerns might potentially be addressed by considering how the concept is defined, and by briefly reviewing the theoretical basis of ecosystem collapse. I then examine the implications of recent research results for the design of ecosystem collapse risk assessments, and the challenges identified in those assessments conducted to date. Recommendations are made regarding how collapse risk assessments might be strengthened based on current scientific understanding, and how this understanding could be improved by further research. In addition, I examine the potential implications for conservation policy and practice if the scientific basis of collapse risk assessments is not strengthened in this way.