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Networks in Plant Epidemiology: From Genes to Landscapes, Countries, and Continents

First author: AgroParisTech, ENGREF, 19 avenue du Maine, 75732 Paris Cedex 15, France, and Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK; first, second, sixth, and ninth authors: Division of Biology, Imperial College London, Silwood Park, Ascot, SL5 7PY, UK: second author: West Virginia University, 1026 Agricultural Science, P.O. Box 6108, Morgantown, WV 26506; third author: Department of Mathematics, University of Trento, 38123 Povo TN, Italy; fourth author: Warwick HRI, University of Warwick, Wellesbourne, Warwick, CV35 9EF, UK; fifth author: CSIRO Ecosystem Sciences, Black Mountain Laboratories, ACT 2601, Australia; seventh author: Plant Pathology, East Malling Research, East Malling, Kent, ME19 6BJ, UK; and eighth author: Forest Pathology & Dendrology, Institute of Integrative Biology, Department of Environmental Sciences, ETH Zurich, 8092 Zurich, Switzerland.

There is increasing use of networks in ecology and epidemiology, but still relatively little application in phytopathology. Networks are sets of elements (nodes) connected in various ways by links (edges). Network analysis aims to understand system dynamics and outcomes in relation to network characteristics. Many existing natural, social, and technological networks have been shown to have small-world (local connectivity with short-cuts) and scale-free (presence of super-connected nodes) properties. In this review, we discuss how network concepts can be applied in plant pathology from the molecular to the landscape and global level. Wherever disease spread occurs not just because of passive/natural dispersion but also due to artificial movements, it makes sense to superimpose realistic models of the trade in plants on spatially explicit models of epidemic development. We provide an example of an emerging pathosystem (Phytophthora ramorum) where a theoretical network approach has proven particularly fruitful in analyzing the spread of disease in the UK plant trade. These studies can help in assessing the future threat posed by similar emerging pathogens. Networks have much potential in plant epidemiology and should become part of the standard curriculum.

Additional keywords: biodiversity, complexity and stability, modeling host–pathogen interactions, network theory, sudden oak death, systems biology.