TABLE CONTENTS

individual nematodes. The MOTUs displayed strong stratification among the three habitats
and a neighbor-joining tree indicated that MOTUs represented a taxonomically broad crosssection
of the phylum. Only six of the MOTUs identically matched sequences deposited in
GenBank. In March 2007 we returned to La Selva to attempt to connect the MOTUs with
morphological assessments of the specimens. Not surprisingly these collections generated
more MOTUs and species identity was not easily recovered. A subset of the MOTUs from
the Criconematoidea will be discussed to illustrate the process of linking the morphological
and molecular data sets.
Genetic Variability of Xiphinema Index, the Nematode Vector of Grapevine
Fanleaf Virus (Gflv), Inferred by Microsatellites Loci and Mitochondrial
Sequences
L. Villate (1,2), M. Van Helden (2), D. Esmenjaud (3) & O. Plantard (1)
(1) INRA, Agrocampus Rennes, UMR BiO3P (Biology of Organisms and Populations applied to Plant
Protection), F-35653 LE RHEU, France; (2) Equipe Zoologie, UMR Santé Végétale, ENITA de Bordeaux,
France; (3) Equipe ‘Interactions Plantes-Nématodes’, UMR IBSV, INRA Sophia Antipolis, France
Xiphinema index is a migratory ectoparasitic nematode and the vector of Grapevine fanleaf
virus (GFLV) causing vine degeneration and considerable yield losses. This nematode,
introduced from the Middle East and worldwide distributed, reproduces by meiotic
parthenogenesis. A better knowledge of its genetic variability will provide important insights
for the development of alternative control strategies to nematicides. Mitochondrial markers
(mainly from the Cytochrome B gene) were developed for a phylogeographical approach at
the world scale. The weak genetic divergence (~1%) between faraway populations did not
bring conclusive information on the native area and suggests that only a limited part of the
native genetic diversity has been introduced into the different vine regions. Nevertheless,
Western populations (California, Chile, Spain, France) belong to the same haplotype and thus
might share a same introduction origin. By contrast Eastern populations show a higher
diversity in agreement with the hypothesis of the Eastern nematode origin. Eight
microsatellite markers were developed for a complementary approach of population genetics,
mainly focused among and within populations at the regional scale of the Bordeaux vineyard.
Results confirm the parthenogenetic status of X. index but also suggest a few events of sexual
reproduction. The genetic structure of populations is characterized by a weak differentiation
between vineyards worldwide, which favors the hypothesis of a same origin of introduction.
By contrast, we observed a strong differentiation between nematodes from different
grapevine fields of the same vineyard, as well as between nematodes from different sampling
points of a same grapevine field. This high genetic diversity observed in the Bordeaux
vineyard suggests multiple introduction events in this region. Moreover, we did not observe
any isolation by distance at both the scales of the Bordeaux region and the grapevine field.
Taken together these results strengthen the hypothesis of limited active and marked passive
dispersals of the nematode (through human activities and grapevine replants).
5 th International Congress of Nematology, 2008 173