H. Lecoq, and
First, third, and fourth authors: INRA, Unité de Pathologie Végétale UR407, F-84140 Montfavet, France; and second author: INRA, Unité de Recherches Plantes et Systèmes de culture Horticoles UR1115, F-84000 Avignon, France.
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Accepted for publication 17 August 2010.
Since 1999, “emerging” (EM) strains of Watermelon mosaic virus (WMV) have been detected in cucurbit crops of southeastern France, probably as a result of recent introductions. Population genetic approaches were used to study the structure of EM isolates in southeastern France and to identify factors involved in their spatial distribution. A population clustering method (SAMOVA) and a maximum-difference algorithm (Monmonier's algorithm) were combined to visualize and quantify barriers to gene flow between populations. Both methods yielded similar results and two main barriers were identified. A North/South oriented barrier may be related to physical obstacles to gene flow (Rhône River, presence of an area with few cucurbit crops). Although the barrier was very strong, some “crossing” events were detected. A second barrier, oriented Northwest to Southeast, was not correlated with obvious geographical features. The two methods used here are complementary and confirm the limited spread of WMV-EM isolates. This approach can be useful in epidemiology studies to characterize the structure of viral populations and identify barriers to gene flow.
epidemiology, potyvirus, spatial structure.
© 2010 The American Phytopathological Society