Potato susceptibility to soft rot caused by Dickeya spp.

Soft rot on potato tubers is caused by bacteria belonging to the genus Pectobacterium and Dickeya. The most often detected species in rotting tubers or plants sampled from Swiss potato lots are Dickeya dianthicola and Dickeya solani. Laboratory tests on tuber slices were set up to determine differences in cultivar susceptibility and isolate aggressiveness. Among the five cultivars tested, Agria was more susceptible than Annabelle. Among the five bacterial isolates tested, the 3 D. solani isolates were in most cases more virulent than the 2 D. dianthicola isolates. Several hypothesis are discussed in this article to explain the differences in cultivar susceptibility and isolate virulence. The results of this study should allow an optimization of the potato storage, after considering the susceptibility of a given cultivar to soft rot development and the aggressiveness of the Dickeya specie which infected the lot.