Biological and molecular properties of a pathotype P-1 and a pathotype P-4 isolate of pea seed-borne mosaic virus

1 Department of Microbiology and Center for Gene Research and Biotechnology, Oregon State University, Corvallis, OR 97331-3804 and 2 Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331-2902, USA Two isolates of pea seed-borne mosaic potyvirus, DPD1 and NY, were identified as pathotypes P-1 and P-4, respectively, by their infectivity on Pisum sativum L. lines homozygous for the recessive resistance genes sbm-1 and sbm-4 . The two isolates differed in several biological characteristics. DPD1 induced transient vein clearing, downward rolling of leaflets and internode shortening on P. sativum , whereas NY only caused a slight growth reduction. DPD1 moved systemically in Chenopodium quinoa whereas NY was restricted to inoculated leaves. DPD1 was frequently transmitted by seeds whereas NY was rarely seed-transmitted: 24% and 0.3%, respectively, in P. sativum ‘549’. Both DPD1 and NY were transmitted by aphids ( Myzus persicae ), though a DAG triplet was not present in the N terminus of the coat protein. The nucleotide sequence and deduced amino acid sequence of NY were determined and compared to the corresponding sequences of DPD1. * Author for correspondence. Present address: The Danish Institute of Plant and Soil Science, Biotechnology Group, Lottenborgvej 2, DK-2800 Lyngby, Denmark. Fax +45 45 87 25 10. e-mail e.johansen@dips-Lyngby.dk Received 19 October 1995; accepted 12 February 1996.