Potato and potato virus Y: the effect of cultivar, seed type, and dfense-inducing agents differences in incidence
Potato (Solanum tuberosum subsp. tuberosum) is an important crop grown worldwide. Propagated vegetatively, a sustainable potato industry relies on pathogen free, tissue culture-produced plantlets to maintain low disease incidence in seed potato stock. Potato virus Y (PVY) infection is the most significant threat to seed potato production. Therefore, determining the influence of cultivar and seed type on PVY incidence could lead to improved management practices. Data from seed potato certification inspection in Montana indicated that plants grown from seed produced in sterile conditions (plantlets and minitubers) had a greater incidence of PVY than plants grown from field-produced tubers. We hypothesized that differences in cultivar, seed type and growth conditions (i.e., sterile vs. field grown) impacted PVY incidence. Systemic acquired resistance (SAR) is a plant immune response that is induced by pathogens and resistance-inducing agents. Resistance-inducing agents are effectively used to limit fungal pathogens, and we hypothesized that they may also limit PVY infection. To test these factors, potato plants (cultivars Russet Burbank and Norkotah Colorado 3) were grown from multiple seed types (i.e., plantlet, minituber, and Generation 3 tuber (G3)) and mechanically inoculated with PVY strain Wilga in the presence and absence of Systemic Acquired Resistance (SAR) inducing agents. Percent infection (incidence) was measured with double-antibody sandwich enzyme-linked immunosorbent assay (DASELISA) at three time points post-inoculation. These studies resulted in the following conclusions: (1) incidence of PVY infection varies by cultivar, specifically, the Russet Burbank cultivar had a lower incidence of PVY than the Norkotah Colorado 3 cultivar, (2) Russet Burbank plants grown from tissue culture plantlets had a higher incidence of PVY infection than Russet Burbank plants grown from field-produced G3) tubers, and (3) phosphorous acid (Phostrol®), an inducer of Systemic Acquired Resistance (SAR) may reduce PVY infection, particularly in Russet Burbank plantlets. These findings advance our understanding of the differences in PVY incidence by cultivar and seed type, and in turn provide valuable information for maintaining pathogen free potato seed.