TRANSFORMATION OF POTATO (CV LATE-HARVEST) WITH THE POTATO LEAFROLL VIRUS COAT PROTEIN GENE, AND MOLECULAR ANALYSIS OF TRANSGENIC LINES

Potato leafroll virus (PLRV) is one of the most destructive potato vir uses in South Africa. In order to establish resistance against PLRV in the potato cultivar Late Harvest, the coat protein (CP) gene of a Sou th African isolate of the virus was isolated, cloned into the plant tr ansformation vector pBII21 and inserted into potatoes using Agrobacter ium tumefaciens-mediated transformation. Six plantlets, which appeared to be phenotypically normal, were regenerated from leaf disks under k anamycin selection. These lines were analysed for stable transgene ins ertion and expression. The presence of the PLRV CP, uidA (GUS) and npt II (kanamycin resistance) genes were shown using PCR: Southern blot an alysis verified that the PLRV CP gene had been inserted into the genom e of the transgenic potato lines. Coat protein could not be detected, but RNA dot blots demonstrated PLRV CP gene expression at the mRNA lev el. Expression of the uidA gene was investigated using a fluorometric assay, and it was observed that lines containing the PLRV CP gene in t he antisense orientation exhibited GUS activity.