Tuesday, 14 December 2010

November review for F1000

This month we decided to review a novel application of network theory to the horticultural industry.  This paper is on work that is still very much evolving, however it shows great potential for further studies of plant trade networks. 

Disease spread in small-size directed trade networks: the role of hierarchical categories  M. Pautasso, X. Xu, M.J. Jeger, T.D. Harwood, M. Moslonka-Lefebvre and L. Pellis Journal of Applied Ecology. 2010 Dec; 47(6):1300-1309
DOI:  10.1111/j.1365-2664.2010.01884.x

Our Review:
Lonsdale M: 2010. F1000.com/6722956

This article is a novel theoretical application of network theory to the horticultural industry, which might ultimately contribute to a better understanding of the way in which plant diseases may spread.

This article demonstrates that structural change in the trade in plants may have an influence on the chances that a disease epidemic will occur. For example, increasing the number of producers and retailers relative to the number of wholesalers will tend to increase epidemic spread in some kinds of networks. In other kinds of networks (called 'scale-free'), which are characterised by super-connected individuals, the relative number of producers and retailers to wholesalers is not a key driver of epidemic spread.

Definitions of network structures are given in the paper and in a companion paper shortly to be published (available now as 'early view') that gives a review of this area and a more in-depth explanation of the terminology [1]. The study of networks in relation to plant diseases is a relatively novel field in comparison with network studies of diseases in humans and animals [2].

The next step for this work will be to align it with 'real' horticultural trade networks, to identify which theoretical representation fits best with existing networks. Once this is established, the findings in this paper may enable hypotheses to be developed on how structural changes in the plant trade will impact on the spread of epidemics and advise management strategies.

A better understanding of horticultural trade networks may equally improve understanding of 'invasion pathways' and for invasive plants themselves, and not just their diseases, as plant invaders are often brought in by trade in the horticultural industry, and their propagation through the trade possibly has epidemic-like properties.
References: [1] Moslonka-Lefebvre et al. Phytopathology 2010, Nov 9, Epub ahead of print 
DOI: 10.1094/PHYTO-07-10-0192
[2] Jeger et al. New Phytol 2007, 174:279-97  DOI: 10.1111/j.1469-8137.2007.02028.x

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