POTATO PLANTS TRANSFORMED WITH A POTATO-VIRUS YP1 GENE SEQUENCE ARE RESISTANT TO PVY-DEGREES

The cloned P1 sequence of PVYO was transferred in sense orientation into the potato cultivar Pito using Agrobacterium-mediated transformation. Sixteen of the putatively transformed plants (NPTII positive) were assayed for PVY(O)resistance. No PVYO was detected in four plants, representing two lines, 21 days after two sap-inoculations and 35 days after graft-inoculation, and the plants remained symptomless, whereas other tested plants showed mosaic symptoms and had high PVY titers similar to those of the control plants. No line was resistant to PVYN and potato viruses A and X. Southern analysis confirmed the presence of the transgene(s) in the two PVYO-resistant and one susceptible line examined, but no signal was detected in non-transformed Pito. These results suggest a high level of protection against PVYO in potato transformed with P1 sequence of PVYO.