Characterization and Molecular Detection of the P4 Pathotype of Pea Seedborne Mosaic Potyvirus

Abstract

The New York isolate of pea seedborne mosaic potyvirus (PSbMV) pathotype P4 was differentiated from the more prevalent PSbMV-P1 pathotype on selected pea cultivars, serologically and by sequence-specific reverse transcription-polymerase chain reaction (RT-PCR). PSbMV-P4 was seed-transmissible at much lower rates than P1 (0 to 0.7% versus 0 to 32%) in selected pea cultivars and was not detectable by enzyme-linked immunosorbent assay (ELISA) in reproductive tissues (pollen or embryo axes) of pea, whereas P1 was readily detectable in these tissues. P4 also was aphid-transmitted at lower rates (4 to 16%) than those of Pl (11 to 40%) and had distinct virus acquisition-time optima. RT-PCR detected approximately 10 pg of P4 RNA per 1.0 μg of total nucleic acids from P4-infected tissues and provided positive pathotype identification in single or mixed infections. RT-PCR and pathotype-selective ELISA were used to determine seed-transmission rates of the two pathotypes in seedling progeny of pea (Pisum sativum) cultivars inoculated with P1, P4, or P1 + P4. There were slight variations in the frequency of P1 seed transmission in the presence of P4; P4 seed-transmission rates did not increase in the presence of P1.