Field resistance to the potato leafroll luteovirus in transgenic and somaclone potato plants reduces tuber disease symptoms

Abstract

Potato plants transformed with one of two potato leafroll luteovirus (PLRV) coat protein cDNA sequences and somaclonal variants recovered from the transformation process were examined to determine agronomic characteristics, incidence and level of resistance to PLRV, and the severity of disease symptoms. In total, 97 genetically modified lines of the potato cultivar Russet Burbank were initially screened in a greenhouse and selected lines subsequently examined in three independent field trials using a multiple year randomized block design. Abnormal plant phenotypes were observed in all lines and included reduced plant height, chlorotic leaves, delayed flowering, abnormal flower structure, and low tuber yields. Mean titres of PLRV in the field experiments, determined by enzyme-linked immunosorbent assay, were reduced by 32% to 71% and the incidence of elevated infection (>0.10 ng of PLRV per mg of leaf tissue) was reduced by 24% to 45% in the modified lines. Resistance to PLRV was sustained with similar virus titres in primary and secondary PLRV infections and was observed through 8 years of vegetative propagation and 5 years of field evaluation. Primary and secondary symptoms of PLRV infection were observed in the modified and wild type plants. However, the incidence and severity of internal tuber necrosis was significantly reduced in each of the modified lines. This is the first report characterising field performance of PLRV resistant plants transformed with the PLRV coat protein cDNA or derived through somaclonal variation.