To induce potato variants with enhanced resistance to common scab disease that retain the desirable agronomic traits of the original cultivars, we used a cell culture technique that employs thaxtomin A, the primary phytotoxin that induces scab symptoms. We induced 24 variants from the potato cultivar ‘Saya-akane’, developed in Japan, and selected two with enhanced resistance to the disease by growing them in planters with bacteria-inoculated soil and in a field infested with the disease. We also examined toxin tolerance in micro-tubers of variants that showed a lower degree or percentage of infection in the glasshouse screening, and found no significant difference relative to the original cultivar. To clarify the effect of using thaxtomin A, we examined the efficiency of induction of the potential enhanced resistance by comparing the degree of infection among variants grown in planters with inoculated soil. We observed no significant difference between variants induced on culture medium with and without the toxin. These results suggest that the effect of using the toxin as a positive selection agent is restrictive and that most resistance-enhancing mutations are induced by the cell culture procedure itself.
