RNA INTERFERENCE FOR SHARKA DISEASE RESISTANCE

Abstract

Sharka is the most important disease of stone fruits in terms of agronomic impact and economic importance. The disease is caused by Plum pox virus (PPV) a single-stranded RNA virus. In a recent work, we transformed Nicotiana benthamiana plants with four PPV sequences, covering the PI and HC-Pro genes, arranged to express self-complementary hairpin RNA. Two lines for each construct were challenged with PPV. All the transgenic plants were resistant to PPV infection, with the exception of a fraction containing the P1/HcPro construct. The P1/HcPro lines, in addition to the type of gene construct utilised, differ from the other lines in that they are multiple copy lines. In the current study, three additional P1/HcPro N. benthamiana lines were analysed. All thirty plants challenged with the Italian ISPaVe44 PPV isolate were fully resistant to the virus infection. Between one and three transgenic loci were present in the transformed lines suggesting that a single transgenic locus was not an absolute prerequisite for obtaining plants completely resistant to PPV infection. Additionally, in order to introduce PPV resistance in Prunus species, transformation techniques were developed for Prunus domestica (plum) 'Stanley'. Transgenic plums were obtained, as confirmed by PCR and histochemical GUS assays.