Sweet potato virus disease (SPVD) is the name used to describe a range of severe symptoms in different cultivars of
sweet potato, comprising overall plant stunting combined with leaf narrowing and distortion, and chlorosis, mosaic or
vein-clearing. Affected plants of various cultivars were collected from several regions of Uganda. All samples
contained the aphid-borne sweet potato feathery mottle potyvirus (SPFMV) and almost all contained the whiteflyborne
sweet potato chlorotic stunt closterovirus (SPCSV). SPCSV was detected by a mix of monoclonal antibodies
(MAb) previously shown to react only to a Kenyan isolate of SPCSV, but not by a mixture of MAb that detected SPCSV
isolates from Nigeria and other countries. Sweet potato chlorotic fleck virus (SPCFV) and sweet potato mild mottle
ipomovirus (SPMMV) were seldom detected in SPVD-affected plants, while sweet potato latent virus (SPLV) was
never detected. Isolates of SPFMVand SPCSV obtained by insect transmissions together induced typical symptoms of
SPVD when graft-inoculated to virus-free sweet potato. SPCSValone caused stunting and either purpling or yellowing
of middle and lower leaves when graft-inoculated to virus-free plants of two cultivars. Similarly diseased naturally
inoculated field plants were shown consistently to contain SPCSV. Both this disease and SPVD spread rapidly in a
sweet potato crop.