Partial characterization of the P4 pathotype of pea seedborne mosaic virus

Graduation date: 1993Biological, serological, and molecular characteristics\ud of the P4 pathotype of pea seedborne mosaic potyvirus\ud (PSbMV) were investigated. The characterization allowed P4\ud to be differentiated from other pathotypes of the same\ud virus.\ud P4 was distinguished from P1 on the basis of host\ud symptomatology. It induced varied, but often distinctive\ud symptoms in systemically-infected pea (Pisum sativum)\ud cultivars. P4 inoculation of indicator hosts, notably\ud Chenopodium album, resulted in the formation of local\ud lesions.\ud Pathotype P4 was seed transmitted at low frequencies\ud relative to P1. In ten selected pea cultivars, seed\ud transmission of P4 never exceeded 0.7%, while P1 was\ud transmitted at frequencies as high as 33%. In mixed\ud infections with P1, pathotype P4 was seed transmitted at 0-\ud 2% as determined by P4-specific indirect ELISA. However,\ud limited polymerase chain reaction (PCR) data suggest that\ud P4 may be transmitted with P1 at higher rates than\ud indicated by ELISA data.\ud P4 was also aphid transmitted at relatively low rates.\ud Pea aphids (Acyrthosiphon pisum) allowed 3 or 5 min\ud acquisition access periods (AAP's) transmitted P4 at a\ud maximum rate of 16% (3 aphids/plant). P4 transmission\ud required short (1-7 min) AAP's and exhibited no bimodal\ud character within tested parameters.\ud P4 could be serologically distinguished from the other\ud pathotypes using monoclonal and polyclonal antibodies.\ud Tests with cross-reactive P4 antiserum suggest that P4 is\ud more closely related to P2 than P1. P4-specific antiserum\ud was derived by cross-absorbing diluted antiserum with P1-\ud infected pea sap to eliminate P1- reactive antibodies.\ud P1 and P4 RNA was detected and differentiated using\ud pathotype-specific oligonucleotide primers in conjunction\ud with PCR. Viral RNA sequences were amplified in pure\ud preparations as well as crude pea tissue (leaf, root,\ud pollen, and seed) extracts