Transgenic potatoes (cv. Late Harvest) show increased tolerance to potato leafroll virus in greenhouse and field trials : research letter

Potato leafroll virus (PLRV; genus lIgPolerovirusl/Ig; family Luteoviridae ) is one of the most important potato viruses in South Africa. In order to introduce resistance against PLRV into the potato cultivar Late Harvest, six transgenic lines expressing the PLRV coat protein ( CP ) gene were previously generated. The tolerance of these lines to PLRV in greenhouse and field trials is reported here. Authorization was obtained from the South African Committee on Genetic Experimentation for the trial, the first field trial of transgenic potatoes in South Africa. All six lines showed tolerance to PLRV in greenhouse trials compared with non-transgenic LH, as determined by PLRV levels in double antibody sandwich-enzyme-linked immunosorbent assays (DAS-ELISA) and by scoring for PLRV symptoms. One line containing the lIgCPl/Ig gene in the antisense orientation, LH13.3, showed the greatest reduction in PLRV symptoms and levels in the greenhouse, but was not more tolerant than nontransgenic LH in the field trial. However, this line showed a better tuber yield than PLRV-infected control LH plants in the field. Another line containing the lIgCPl/Ig gene in the antisense orientation, LH13.4, showed the greatest reduction in PLRV symptoms and levels in the field, but had a low tuber yield and displayed an abnormal, curled tuber form.