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Sweetpotato virus disease (SPVD), the most important disease affecting sweetpotato (Ipomoea batatas (L.) Lam), is caused by the synergistic interaction of the aphid-transmitted Sweetpotato feathery mottle virus (SPFMV) and whitefly-transmitted Sweetpotato chlorotic stunt virus (SPCSV). In this study, SPVD was the main disease in the Cañete Valley, the major sweetpotato-producing area in Peru. Studies on virus incidence showed that SPCSV and SPFMV were the most frequently identified viruses in Cañete Valley. Symptoms of different severity were associated with isolates of both viruses involved in the SPVD. Over 80% of plants infected with both SPFMV and SPCSV showed the symptoms (leaf reduction and deformation, vein clearing or mosaic, and stunting) typically attributed to SPVD elsewhere. SPFMV did not significantly affect the yield of the sweetpotato cultivars Jonathan and Costanero, but infection of these cultivars by SPCSV was associated with significant yield reduction. Double infection by the two viruses resulted in SPVD and greater yield reduction than for either alone. These results demonstrate that SPFMV and SPCSV interact synergistically and that the severity of SPVD symptoms also depends on the particular isolate of each virus.
Gutiérrez et al. (Sat,) studied this question.