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

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.