Fig. 3

Characterization of viral infection, distribution, and accumulation in plants grown at NaPPI. a Detached leaves from wild-type sweetpotato plants infected with only SPFMV (Wt-F) or SPCSV (Wt-C) or co-infected with SPFMV and SPCSV (Wt-FC) at 31 dpt. Numbers above the leaves indicate leaf order on the plant from top to bottom. Black arrows indicate typical mosaic symptoms on older leaves of Wt-C plants, whereas leaf deformation and vein clearing can be observed on almost all leaves of Wt-FC plants. Holes (black circles) on leaves correspond to the sampling regions for the viral accumulation assay. B SPCSV and SPFMV distribution from top to bottom leaves in Wt-F, Wt-C, and Wt-FC sweetpotato plants. Leaf numbering along the x axis corresponds to the sampling leaf order in A. The black arrow indicates the cross-over point around leaf five between SPCSV and SPFMV localization in Wt-FC plants. Data are expressed as the mean ± SD from two sample pools representing four plants in total. C Relative quantification of viral accumulation among all six sweetpotato treatment groups. Viral accumulation was estimated at 31 dpt in plants grown at NaPPI by measuring the relative gene expression of viral coat protein (SPFMV-CP and SPCSV-CP) and RNAse III of SPCSV (SPCSV-R3). Relative gene expression of SPCSV-CP and SPCSV-R3 were not assayed in transgenic plants (R3-H and R3-F) and wild-type plants (Wt-H, Wt-F, Wt-C and Wt-FC), respectively. The actin housekeeping gene was used for RT-qPCR normalization. Data are shown as the mean ± 95% CI (n = 10–12)