ROLE OF ACQUISITION AND INOCULATION TIME IN THE EXPRESSION OF CLONAL VARIATION FOR BYDV-PAV TRANSMISSION IN THE APHID SPECIES RHOPALOSIPHUM-PADI

Vector efficiency of 20 Rhopalosiphum padi clones, originating from Eu rope, North America and North Africa and exhibiting different types of life cycle, was evaluated by transmitting a French BYDV-PAV isolate t o barley plants under five different acquisition/inoculation sequences (AAP/IAP). Differences between clones in transmission efficiency were found only when a short AAP was followed by a long LAP (6 h/120 h) an d, to some extent, when a long AAP (48 h) was followed by a short IAP (6 h), but no differences were found when the conditions for virus tra nsmission were optimal, i.e. long AAP followed by long IAP (48 h/120 h ). There were no differences in transmission rates by clones of differ ent geographical origins and with different life cycles. As a conseque nce, clonal variation is probably of little importance in the vector a spects of the epidemiology of PAV serotypes transmitted by R. padi, bu t the availability of a range of clones exhibiting transmission differ ences under limiting AAP or IAP conditions could be of interest for st udies of virus-vector relationships.