Incidence of six potato virus es in spring, summer and autumn potato crops of the North West Frontier Province of Pakistan

Spring, summer and autumn potato crops, grown in three different ecological zones (Peshawar, Swat and Hazara districts, respectively) in the North West Frontier Province of Pakistan were surveyed for potato viruses during 1999. A total of 1338 samples from 76 fields was tested by dot-immunobinding assay using antisera to six different viruses. Two major aphid-borne viruses, Potato leaf roll virus and Potato virus Y (PVY), were frequently detected in potato crops with incidences rangin g from 0–14.7% in spring crops, 1.8–45.5% in summer crops, and 0–71.0% in autumn crops. Three other viruses, Potato virus A, Potato virus S and Potato virus X (PVX), were also detected but they were primarily limited to the summer crop, with incidences of 0–5.5%,0–3.4% and 1.4–8.3%, respectively. PYX was also noted in the spring crop, with an incidence of 0–3.2%. None of the samples tested positive for Potato virus M. PVY was detected in 6–52% of potato tubers collected from potato growers in the Peshawar district.