Early season survey of pea viruses in Pakistan and the detection of two new pathotypes of pea seedborne mosaic potyvirus

Sixty-two commercial pea fields or experimental plots located in eight districts of the major pea-growing areas of North West Frontier Province (NWFP) of Pakistan were surveyed for pea viruses in the early winter growing season of 1995. Samples were analyzed by dot-immunobinding assay (DIBA) using antisera to 14 different viruses. Of the 713 plants sampled, 82 were positive for either bean yellow mosaic potyvirus, cucumber mosaic cucumovirus, or pea seedborne mosaic potyvirus (PSbMV), with an average incidence of 9.4, 0.57, and 1.5%, respectively. PSbMV was also detected in 1 to 5% of dry seed from five of the 12 pea varieties tested and in 8 to 20% of seedlings raised from seed of three of these varieties. The infectivities of 12 PSbMV isolates found in the survey of pea varieties from Pakistan were compared using a standard range of pea differential genotypes, and the isolates were classified into four distinct pathotypes. Four isolates were classified as pathotype P-l and two as P-4. The remainder did not fit into the existing PSbMV pathotype classification and were tentatively placed into two other groups named U-l and U-2.