Reduced field spread of potato leafroll virus in potatoes transformed with the potato leafroll virus coat protein gene

Russet Burbank potato was transformed with plant expression vectors containing the potato leafroll luteovirus (PLRV) coat protein (CP) gene. Transgenic potato lines contained a gene expression cassette with two copies of a PLRV CP gene in which the nucleotide sequence was modified to improve expression of the gene. In addition, the two copies of the PLRV CP gene were each driven by a different promoter. Field test screening for PLRV resistance identified 15 lines which showed moderate resistance to PLRV infection and virus titer build-up and a longer incubation period for systemic infection. By conducting field resistance assays during a period when the vector of PLRV was not present, it was possible to test whether the observed resistance was sufficient to restrict aphid transmission of PLRV in a field test. Two years of field testing demonstrated that PLRV-spread from an infected plant to adjacent healthy plants of the same line was severely restricted in nearly all the transgenic lines in the field. These lines have useful resistance to PLRV and could aid in managing PLRV disease in Russet Burbank potato.