CRISPR-Cas9 Targeting of the Gene Extends the Potato Virus Y Resistance Spectrum of the L. cv. Desirée.

Translation initiation factors and, in particular, the eIF4E family are the primary source of recessive resistance to potyviruses in many plant species. However, no eIF4E-mediated resistance to this virus genus has been identified in potato ( L.) germplasm. As in tomato, the potato eIF4E gene family consists of , its paralog , and . In tomato, knockout (KO) confers resistance to a subset of potyviruses, while the double KO, although conferring a broader spectrum of resistance, leads to plant developmental defects. Here, the tetraploid potato cv. Desirée owning the dominant gene conferring resistance to potato virus Y (PVY) strain O but not NTN was used to evaluate the possibility to expand its PVY resistance spectrum by CRISPR-Cas9-mediated KO of the susceptibility gene. After a double process of plant protoplast transfection-regeneration, KO potatoes were obtained. The knockout was specific for the , and no mutations were identified in its paralog. Expression analysis of the eIF4E family shows that the disruption of the does not alter the RNA steady-state level of the other family members. The KO lines challenged with a PVY isolate showed a reduced viral accumulation and amelioration of virus-induced symptoms suggesting that the gene was required but not essential for its multiplication. Our data show that editing can be usefully exploited to broaden the PVY resistance spectrum of elite potato cultivars, such as Desirée, by pyramiding eIF4E-mediated recessive resistance.