Crop variety mixtures have the potential to increase yield stability in highly variable and unpredictable environments, yet knowledge of the specific mechanisms underlying enhanced yield stability has been limited. Ecological processes in genetically diverse crops were investigated by conducting field trials with winter barley varieties (Hordeum vulgare), grown as monocultures or as three-way mixtures in fungicide treated and untreated plots at three sites. Mixtures achieved yields comparable to the best performing monocultures whilst enhancing yield stability despite being subject to multiple predicted and unpredicted abiotic and biotic stresses including brown rust (Puccinia hordei) and lodging. There was compensation through competitive release because the most competitive variety overyielded in mixtures thereby compensating for less competitive varieties. Facilitation was also identified as an important ecological process within mixtures by reducing lodging. This study indicates that crop varietal mixtures have the capacity to stabilise productivity even when environmental conditions and stresses are not predicted in advance. Varietal mixtures provide a means of increasing crop genetic diversity without the need for extensive breeding efforts. They may confer enhanced resilience to environmental stresses and thus be a desirable component of future cropping systems for sustainable arable farming.

Background and AimsPlant genotypic mixtures have the potential to increase yield stability in variable, often unpredictable environments, yet knowledge of the specific mechanisms underlying enhanced yield stability remains limited. Field studies are constrained by environmental conditions which cannot be fully controlled and thus reproduced. A suitable model system would allow reproducible experiments on processes operating within crop genetic mixtures.MethodsPhenotypically dissimilar genotypes of Arabidopsis thaliana were grown in monocultures and mixtures under high levels of competition for abiotic resources. Seed production, flowering time and rosette size were recorded.Key ResultsMixtures achieved high yield stability across environments through compensatory interactions. Compensation was greatest when plants were under high levels of heat and nutrient stress. Competitive ability and mixture performance were predictable from above-ground phenotypic traits even though below-ground competition appeared to be more intense.ConclusionsThis study indicates that the mixing ability of plant genotypes can be predicted from their phenotypes expressed in a range of relevant environments, and implies that a phenotypic screen of genotypes could improve the selection of suitable components of genotypic mixtures in agriculture intended to be resilient to environmental stress.

BACKGROUND The impetus to adopt integrated pest management (IPM) practices has re‐emerged in the last decade, mainly as a result of legislative and environmental drivers. However, a significant deficit exists in the ability to practically monitor and measure IPM adoption across arable farms; therefore, the aim of the project reported here was to establish a universal metric for quantifying adoption of IPM in temperate arable farming. This was achieved by: (i) identifying a set of key activities that contribute to IPM; (ii) weighting these in terms of their importance to the achievement of IPM using panels of expert stakeholders to create the metric (scoring system from 0 to 100 indicating level of IPM practised); (iii) surveying arable farmers in the UK and Ireland about their pest management practices; and (iv) measuring level of farmer adoption of IPM using the new metric. RESULTS This new metric was found to be based on a consistent conception of IPM between countries and professional groups. The survey results showed that, although level of adoption of IPM practices varied over the sample, all farmers had adopted IPM to some extent (minimum 27.2 points, mean score of 65.1), but only 13 of 225 farmers (5.8%) had adopted more than 85% of what is theoretically possible, as measured by the new metric. CONCLUSION We believe that this new metric would be a viable and cost‐effective system to facilitate the benchmarking and monitoring of national IPM programmes in temperate zone countries with large‐scale arable farming systems. © 2019 Society of Chemical Industry

Summary Experiments were conducted on the role of intra‐ and inter‐genotypic competition in ecological processes operating at the population scale in diseased plant populations.Combinations of Arabidopsis thaliana genotypes showing variation for phenotypic traits relating to competitive ability and pathogen compatibility were infected with the oomycete Hyaloperonospora arabidopsidis and Turnip yellows virus in separate experiments. Plant fitness and competitive ability were estimated from phenotypic measurements.Pathogen‐induced reduction in competitive ability for susceptible genotypes increased the competitive ability of resistant genotypes, resulting in maintenance of yield via competitive release. The two diseases had different effects on competitive interactions between plants. In experiments involving the oomycete, the highest yields were produced by mixtures of two weakly competing genotypes.The Arabidopsis model system has elucidated the ecological processes by which compensatory competitive interactions can increase the buffering capacity of plant populations under pathogen attack. Highly competitive genotypes may not maximize the productivity of the population as a whole, as they may over‐yield at the expense of less competitive, more productive genotypes. The specific outcomes of competitive interactions cannot be generalized because they depend on the disease and the host genotypes.

A crops ability to both suppress weed growth and tolerate weed competition is a key consideration when taking an agroecological approach to weed management. Amongst other cereals, oats are widely considered to have superior weed competitiveness yet studies examining competitive ability of oat varieties are rare. We investigated the ability of oats to suppress weeds and yield in the presence of competition from weeds in trials involving five husked and three naked oat varieties at an organic site in the east of England over four trial years . We identified a number of key traits that were important for weed suppression including establishment rate, tillering ability, and early leaf area index (LAI) which highlight the importance of rapid early growth rate. Furthermore, taller varieties tended to be more weed tolerant but not necessarily more suppressive. Trade-offs between competitive traits and yield were not found in this study. Crop tillering ability was highlighted as an important trait for selection due to its beneficial effects on weed suppression as well as grain yield and also its high heritability. Nomenclature: Winter oat, Avena sativa L.

Ramularia collo‐cygni , the agent responsible for Ramularia leaf spot disease of barley, possesses many mechanisms for avoiding detection by the host, which enables it to survive as an endophyte for much of the plant's life cycle before eventually turning pathogenic. The fungus has also eluded farmers and scientists for decades as it is a late season disease that often displays symptoms after the last possible fungicide intervention when crop scouting for disease has been completed. Visual symptoms are also hard to distinguish from other pathogens, which has resulted in misdiagnoses. The ability of the fungus to spread not only via infected seed but also on infected straw and wind dispersal, coupled with its ability to rapidly evolve resistance to fungicides, has resulted in an escalation in the perceived threat it presents to barley production worldwide. A greater understanding of the plant–fungus interaction is required if future control strategies are to be successful. Key Concepts Plant–fungi interactions can be complex and highly variable, including mutualism, parasitism and commensalism. Global movement of seed can significantly influence the spread of seed‐borne diseases. Plant breeding for disease control requires identification of a suitable breeding target, which may be challenging. Breeding for resistance to one pathogen may lead to control issues for another pathogen. Integrated pest management practices must consider nonchemical control measures and, when using pesticides, antiresistance strategies. Single‐site fungicides are vulnerable to losses in efficacy due to the evolution of resistance in the pathogen population.

BACKGROUND Arable crops in temperate climatic regions such as the UK and Ireland are subject to a multitude of pests (weeds, diseases and vertebrate/invertebrate pests) that can negatively impact productivity if not properly managed. Integrated pest management (IPM) is widely promoted as a sustainable approach to pest management, yet there are few recent studies assessing adoption levels and factors influencing this in arable cropping systems in the UK and Ireland. This study used an extensive farmer survey to address both these issues. RESULTS Adoption levels of various IPM practices varied across the sample depending on a range of factors relating to both farm and farmer characteristics. Positive relationships were observed between IPM adoption and farmed area, and familiarity with IPM. Choice of pest control information sources was also found to be influential on farmer familiarity with IPM, with those who were proactive in seeking information from impartial sources being more engaged and reporting higher levels of adoption. CONCLUSION Policies that encourage farmers to greater levels of engagement with their pest management issues and more proactive information seeking, such as through advisory professionals, more experienced peers through crop walks, open days and discussion groups should be strongly encouraged.

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