Genetic structure of Bemisia tabaci Med populations from home-range countries, inferred by nuclear and cytoplasmic markers: impact on the distribution of the insecticide resistance genes.
BACKGROUND
Insecticide resistance management in Bemisia tabaci is one of the main issues facing agricultural production today. An extensive survey was undertaken in five Mediterranean countries to examine the resistance status of Med B. tabaci species in its range of geographic origin and the relationship between population genetic structure and the distribution of resistance genes. The investigation combined molecular diagnostic tests, sequence and microsatellite polymorphism studies and monitoring of endosymbionts.


RESULTS
High frequencies of pyrethroid (L925I and T929V, VGSC gene) and organophosphate (F331W, ace1 gene) resistance mutations were found in France, Spain and Greece, but not in Morocco or Tunisia. Sequence analyses of the COI gene delineated two closely related mitochondrial groups (Q1 and Q2), which were found either sympatrically (Spain) or separately (France). Only Q1 was observed in Greece, Morocco and Tunisia. Bayesian analyses based on microsatellite loci revealed three geographically delineated genetic groups (France, Spain, Morocco/Greece/Tunisia) and high levels of genetic differentiation even between neighbouring samples. Evidence was also found for hybridisation and asymmetrical gene flow between Q1 and Q2.


CONCLUSIONS
Med B. tabaci is more diverse and structured than reported so far. On a large geographic scale, resistance is affected by population genetic structure, whereas on a local scale, agricultural practices appear to play a major role.
IRD UMR (INRA/IRD/Cirad/Montpellier SupAgro) Centre de Biologie pour la Gestion des Populations, Montferrier-sur-Lez, France.
Nathalie
N
Gauthier
Cécile
C
Clouet
Andreas
A
Perrakis
Despoina
D
Kapantaidaki
Michel
M
Peterschmitt
Anastasia
A
Tsagkarakou
D000818:Animals; D001483:Base Sequence; D005260:Female; D051456:Gene Flow; D005828:Genetics, Population; D006430:Hemiptera / Q000145:classification* / Q000235:genetics* / Q000382:microbiology; D007305:Insecticide Resistance / Q000235:genetics*; D007306:Insecticides / Q000494:pharmacology*; D019083:Mediterranean Region; D018895:Microsatellite Repeats; D010755:Organophosphates / Q000494:pharmacology*; D058974:Phylogeography; D011722:Pyrethrins / Q000494:pharmacology*; D013559:Symbiosis; D020577:Wolbachia
D007306:Insecticides; D010755:Organophosphates; D011722:Pyrethrins
Med Bemisia tabaci; Wolbachia; ace; gene flow; kdr; mitochondrial types; target-site resistance mutations