Potential and limitations of plant virus epidemiology: lessons from the Potato virus Y pathosystem

Abstract Plant virus epidemiology provides powerful tools to investigate key factors that contribute to virus epidemics in agricultural crops. When successful, epidemiological approaches help to guide decisions regarding plant protection strategies. A recent example is epidemiological research on Potato virus Y (PVY) in Finnish seed potato production; this study led to the dentification of the main PVY vector species and helped to determine the timing of virus transmission. However, pathosystems rarely allow research to produce such clear-cut results. In fact, the notorious complexity of plant virus pathosystems, with multiple interactions between virus, vector, plant and environment, makes them often impenetrable even for advanced epidemiological models. This dynamic complexity questions the universal validity of employing epidemiological models that attempt to single out key factors in plant virus epidemics. Therefore, a complementary approach is needed that acknowledges the partly indeterministic nature of complex and evolving pathosystems. Such an approach is the use of diversity, imploying functionally complementary elements that can jointly buffer against environmental changes. I argue that for a wider range of plant production problems, the strategy of combining mechanistic and diversity-based approaches will provide potent and sustainable solutions. In addition, to translate insights from plant virus epidemiology into practice, improvements need to be made in knowledge transfer, both within the scientific community and between researchers and practitioners. Finally, moving towards more appropriate virus control strategies is only possible if economic interests of all stakeholders are in line with changing current practices

There is nothing like an oat

The items reports on first year trials in of the “Quoats” project. It’s well known that oats are generally a good fit in organic rotations and the “Quoats” project – Harnessing new technologies for sustainable oat production and utilisation – aims to make them even better. This five year (2009 – 2014) research project, led by IBERS, Aberystwyth University, brings together a wide range of organisations in the supply chain, from breeders to end-users, to improve the quality and performance of oats. As part of the project, ORC is carrying out field trials to assess the suitability of new oat lines for organic management systems, with particular emphasis on nutrient use efficiency. Eight varieties are being trialled at Wakelyns Agroforestry, Suffolk, including some naked oats, i.e. hull-less oats. The paper reports some first results

Legume Pick ‘n’ Mix

In Spring 2009, ORC set up a legume trial on an organic farm, Barrington Park in Gloucestershire, as part of a large research project called Legume LINK. One of its aims is to compare the performance of several legume and grass species for use in fertility building leys. ORC researchers Thomas Döring and Oliver Crowley report that the trial shows the advantage of mixing species grows over time

What Do We Know About Geographical Knowledge Spillovers and Regional Growth? A Survey of the Literature

Modern (endogenous) growth theory tells us that knowledge spillovers are crucial for the growth of high-income economies. Against this background the paper provides a survey of theoretical and empirical findings highlighting the question of how geographically limited knowledge diffusion can help to explain clusters of regions with persistently different levels of growth. The paper discusses this topic in two steps: First, the theoretical concept of knowledge spillovers is outlined by discussing the different types of knowledge, the spatial dimension of knowledge spillovers, and the geographical mechanisms and structural conditions of knowledge diffusion. This discussion shows that the literature on knowledge spillovers focuses on the hypotheses that such spillovers lead to dynamic externalities and – in the geographical dimension – to agglomeration effects, both of which constitute path dependence in the economic growth of regions. Second, the paper analyses the empirical evidence for these theoretical findings. Existing empirical work mainly supports the theoretically derived hypotheses. This applies especially with focus on the spatial limited character of knowledge spillovers as well as the importance of knowledge transfer for regional productivity and innovative behaviour. --knowledge spillovers,regional growth,research and development,innovation,diffusion of innovations

Regression calibration for Cox regression under heteroscedastic measurement error - Determining risk factors of cardiovascular diseases from error-prone nutritional replication data

For instance nutritional data are often subject to severe measurement error, and an adequate adjustment of the estimators is indispensable to avoid deceptive conclusions. This paper discusses and extends the method of regression calibration to correct for measurement error in Cox regression. Special attention is paid to the modelling of quadratic predictors, the role of heteroscedastic measurement error, and the efficient use of replicated measurements of the surrogates. The method is used to analyze data from the German part of the MONICA cohort study on cardiovascular diseases. The results corroborate the importance of taking into account measurement error carefully

Saving fuel with non-inversion tillage

The mouldboard plough is the traditional and proven method of preparing a seedbed for drilling and controlling arable weeds. However there is a downside; trials have shown deterioration in structural stability, losses of soil organic matter, poor moisture retention and infiltration rates (Riley et al 2008). Farmers have long been aware of these adverse impacts of mouldboard ploughing, but concerns over the greenhouse gas emissions associated with tractor usage have prompted a fresh look at cultivations. ORC researchers, Oliver Crowley, Jemima Showering and Thomas F. Döring consider the case for non-inversion tillage

Using minimum tillage to improve the efficiency of ecosystem service delivery on organic farms

Organic farming practices aim to maximise the delivery of ecosystem services in the agricultural landscape. However, in order to maintain optimal crop productivity the mouldboard plough is often used to control weeds and this can have negative effects on a range of soil parameters, thereby jeopardizing delivery of these services. Reduced tillage (RT) can be beneficial to soils and could improve both the efficiency of production and the delivery of ecosystem services on organic farms. However, abandoning the plough on organic farms is challenging due to impaired weed control. Here we report on a two year trial where an RT system with the Ecodyn, with duck feet shares operating at a depth of 7.6 cm in combination with seed drilling, was compared with mouldboard ploughing. Spring oat and spring barley establishment was improved under RT. Weed cover and biomass was greater under RT, but there was no difference in cereal grain yields in either year. The RT system used 71% less fuel and tillage operations took 72% less time that the plough system

Unleashing the potential of genitic diversity for organic plant breeding

Organic farming, despite its past successes, faces major challenges. A key problem is the lack of suitable plant varieties adapted to the specifi conditions of organic systems. This issue can only be resolved if organic plant breeding efforts are better coordinated and if the potential of plant genetic diversity is unlocked

Oat variety characteristics for suppressing weeds

Oats are a valuable food source and useful in the crop rotation both in organic and conventional farming systems, partly because of their excellent weed suppression ability. Thomas Döring, Louisa Winkler and Nick Fradgley report new results that show how plant breeding can make oats even better

Against the grain

An Organic Research Centre project is examining how diversity-based tools can assist in the on-farm improvement of organic wheat. Successful organic crop production requires varieties that are resistant to diseases, competitive against weeds, and effective at scavenging nutrients. Yet conventional plant breeding has largely neglected organic systems by breeding varieties exclusively for high input conditions. As a consequence, organic producers currently do not have enough choice of plant varieties for organic conditions. One way to expand the choice is to create plant diversity anew and subject it to natural selection on organic farms. After several generations the dominating plants would be better suited to organic systems. This idea is being tested in the Organic Research Centre’s Wheat Breeding LINK project