Importance of Capsid Integrity for Interference Between Two Isolates of Barley Yellow Dwarf Virus in an Aphid

Abstract

Fewer aphids (M. avenae) transmitted the PAV [plant associated virus] isolate of barley yellow dwarf virus (BYDV) if they had first acquired the MAV [Macrosiphum associated virus] isolate, than if they had previously fed on healthy oats or on oats infected with other BYDV isolates. MAV irradiated with UV light for 30 s or more, no longer interfered with PAV transmission when the 2 viruses were injected simultaneously into aphids. Irradiation of MAV decreased both MAV transmission by injected aphids and recognition by MAV-specific antibody, indicating alteration of MAV capsid conformation. No morphological differences between particles irradiated for 15-60 s and those of nonirradiated controls were detected by EM. Some particles irradiated for 120 s appeared to be swollen. Several minutes of irradiation were required for particle disruption. It is suggested that the altered MAV particles do not attach to receptors in aphid salivary glands and are neither transmitted nor able to compete with PAV for common receptor sites that recognize both viruses.