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 Europe, North America and North Africa and exhibiting different types of life cycle, was evaluated by transmitting a French BYDV-PAV isolate to 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) and, 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 transmission were optimal, i.e. long AAP followed by long IAP (48 h/120 h). There were no differences in transmission rates by clones of different geographical origins and with different life cycles. As a consequence, clonal variation is probably of little importance in the vector aspects of the epidemiology of PAV serotypes transmitted by R. padi, but the availability of a range of clones exhibiting transmission differences under limiting AAP or IAP conditions could be of interest for studies of virus-vector relationships.