Vascular cell alterations and predisposed xylem infection in oats by inoculation with paired barley yellow dwarf viruses.
Electron microscope studies of tissue doubly infected with Sitobion avenae-specific and Rhopalosiphum padi-specific variants of barley yellow dwarf virus revealed four types of alteration patterns in infected phloem cells not previously observed in tissue infected with either isolate alone. Cells with alteration patterns similar to those in tissue singly infected with either variant were also present. Double infections with isolates MAV (S. avenae-specific) and RPV (R. padi-specific) predisposed the xylem to infection. This may be the first report of a breakdown in tissue specificity induced by double infection with plant viruses. Double infections with two similar isolates, 6407 (S. avenae-specific) and 6524 (R. padi-specific), failed to predispose the xylem to infection. The paucity of infected cells in tissues with double infections of isolates MAV and RPV compared with the abundance in double infections with 6407 and 6524, suggested interference in the plant between MAV and RPV.
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Agriculture Canada, Research Station, 195 Dafoe Road, Winnipeg, Manitoba R3T 2M9, Canada.
Chong
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