Interactions Among Sweet potato chlorotic stunt virus and Different Potyviruses and Potyvirus Strains Infecting Sweetpotato in the United States.

Sweet potato virus disease (SPVD) is the most serious viral disease of sweetpotato globally. This disease is caused by the synergistic interaction between the aphid-transmitted potyvirus Sweet potato feathery mottle virus (SPFMV) and the whitefly-transmitted crinivirus Sweet potato chlorotic stunt virus (SPCSV). In sweetpotato, titers of SPFMV have been shown to be significantly enhanced when coinfecting with SPCSV. In this study, the effect of SPCSV on titers of different potyviruses and potyvirus strains infecting sweetpotato in the United States was investigated using real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR). No significant difference was observed in titers of the russet crack strain of SPFMV (SPFMV-RC), Ipomoea vein mosaic virus (IVMV), and Sweet potato virus G (SPVG) between single and mixed infections. Titers of all potyviruses and potyvirus strains evaluated were enhanced in the presence of SPCSV, suggesting that a conserved mechanism may underlie these interactions. Titers of the common strain of SPFMV (SPFMV-C), which did not cause SPVD-like symptoms when coinfecting with SPCSV, were also significantly enhanced in the presence of SPCSV. Furthermore, titers of SPCSV were found to be lower in treatments involving pairwise infections compared with plants infected by SPCSV alone. The degree of potyvirus titer enhancement did not correspond to the severity of symptoms observed in certain treatments involving pairwise infections.