Barley Yellow Dwarf Luteovirus (BYDV) Infectivity of Alate Aphid Vectors in Northeast Spain

Rhopalosiphum padi and Sitobion avenae alates were collected from colonised winter cereals and maize in N.E. Spain and fed on young wheat plants for 7-10 days in the glasshouse. Then, aphids were killed and the plants on which aphids reproduced were kept in the glasshouse for 30-40 days. ELISA of infested plants was made using polyclonal and monoclonal antisera against PAV-, RPVand MAV-hke isolates. In autumn and spring, MAV serotypes were transmitted by S. avenae and R. padi, mainly in mixed infections with PAV serotypes. This possibly explains the high frequency of MAV-like isolates and their previously recorded year-to-year stability in maize, grain and forage winter cereals and cerea! volunteers. PAV-like isolates were rarely transmitted by S. avenae and its spread thus depends almost exclusively on R. padi. These results confirm the importance of forage cereals and cereal volunteers as virus sources for winter cereal infection in the autumn, and the latter as a source of BYDV for maize in spring. Zusammenfassung