Résumé
Vector efficiency of 44 clonal lines (clones) of Sitobion avenae belonging to 31 different genotypes (distinct patterns for five microsatellite loci) originating from Western France was evaluated by transmitting the isolate PAV4 of BYDV-PAV to barley seedlings. Variation in transmission rates from 3.7% to 92.5% was observed, with significant effects of the aphid clone, of the plant species on which clones were collected, and of the reproductive mode of the clones. When genotypes are considered instead of clones, a continuum in transmission rates was observed. A subset of S. avenae clones was tested for transmission of one (10 clones) and 13 (4 clones) other BYDV-PAV isolates, and a clear clone effect modulated by an isolate effect was observed. Crosses were made between clones with different vectoring phenotypes and their F1 progeny were tested for PAV4 transmission. The narrow sense heritability of the PAV transmission character was rather high in the F1 families (h(2)=0.5)! and the segregation analyses suggested an oligo/polygenic determinism of this character. The possibility of generating new transmission variants by sexual reproduction and its consequences on transmission mechanism studies and on BYD epidemics are discussed