SPATIAL PATTERN AND GENETIC STRUCTURE OF PPV-M IN A DELIMITED AREA OF STONE FRUIT ORCHARDS IN SOUTHERN FRANCE

The spatial pattern and genetic structure of the Plum pox virus strain M have been studied in a delimited area of ca. 450 ha of stone fruit orchards. In this area, the Sharka disease spread undetected until its discovery in 2004. An exhaustive mapping of the diseased trees was performed using GIS technology in 2004 and 2005. Samples constituted by a pool of flowers or leaves were taken from each diseased tree. Analyses of the genetic structure of the virus populations have been initiated using Capillary Electrophoresis-Single Strand Conformation Polymorphism (CE-SSCP). Each haplotype detected by SSCP was further characterized by direct sequencing of the PCR products. The genetic diversity of PPV populations was low with one major haplotype representing 73% of the collected samples. Three other haplotypes from the 37 detected were found on more than 10 trees. Despite this low diversity, genetic variation had a clear spatial structure.