Determination of aphid transmission efficiencies for N, NTN and Wilga strains of <i>Potato virus Y</i>

Abstract

Potato virus Y (PVY, genus Potyvirus , family Potyviridae ) causes high economic losses worldwide, especially in the production of seed potatoes ( Solanum tuberosum). PVY control systems rely on measuring virus pressure and vector pressure in the field. Calculation of the vector pressure is based on the relative efficiency factors (REFs) of aphid species. These REFs express the transmission efficiency of aphid species in relation to the transmission efficiency of Myzus persicae , the most efficient vector of PVY. In this paper, we report on the determination of aphids' relative transmission efficiency factors (REFs) for isolates of the PVY strains PVY N , PVY NTN and PVY N‐Wi . Biotype Mp2 of M. persicae was tested for its transmission efficiency for six PVY isolates (one PVY N , three PVY NTN and two PVY N‐Wi isolates) and showed comparable average transmission efficiencies for all isolates. The transmission rate of this biotype for the six PVY isolates was set to 1 and Mp2 was used as an internal control in transmission experiments to determine the REFs of three other biotypes of M. persicae and 16 other aphid species (three biotypes per species when available) for the six PVY isolates. Comparing the calculated REFs for PVY N with the REFs reported in the previous century for PVY N , we observe overall comparable REFs, except for Aphis fabae , Aphis spp., Hyperomyzus lactucae, Macrosiphum euphorbiae and Rhopalosiphum padi , which have a lower REF in our experiments, and Aphis frangulae and Phorodon humuli , which have now a higher REF. Comparing the new REFs found for the PVY NTN strains with the new REFs for PVY N , we observe that they are overall comparable, except for A. frangulae (0.17 compared with 0.53) and Schizaphis graminum (0.05 compared with 0.00). Comparing the REFs calculated for PVY N‐Wi with those calculated for PVY N , we can observe six aphid species with higher REFs ( Acyrthosiphon pisum, A. fabae, Aphis nasturtii, Aphis spp., P. humuli and R. padi ). Only the species A. frangulae shows a lower REF for PVY N‐Wi compared with the transmission efficiency of PVY N . Three aphid species ( Aulacorthum solani , Myzus ascalonicus and S. graminum ) for which no REF was determined earlier were found to be capable to transmit PVY and their REFs were determined.