Soft-rot Resistance of Coloured Potato Cultivars (Solanum tuberosum L.): The Role of Anthocyanins

Coloured potatoes (Solanum tuberosum L.) rich in anthocyanins are gaining increasing interest on the markets, mainly due to beneficial health effects. Potato varieties containing colour pigments are therefore utilized more and more in actual breeding programmes. In this study, 10 purple-fleshed potato cultivars were compared in their resistance to soft rot caused by Pectobacterium carotovorum (Pc) with 10 white/yellow-fleshed potato cultivars. The results revealed that coloured potato cultivars exhibited on average better resistance to soft rot than white/yellow-fleshed potato cultivars. On tuber halves of purple-fleshed cultivars, the extent of rotting caused by Pc was on average 28.6% lower than on white/yellow-fleshed cultivars. The greater resistance of coloured potatoes coincided with the presence of anthocyanins, higher concentrations of soluble phenols and elevated polyphenol oxidase activity in tuber tissue. These three components were significantly correlated with the extent of rotting caused by Pc. However, coloured and white/yellow-fleshed cultivars were not very different in phenylalanine ammonia-lyase and peroxidase activity. There were also no significant differences in concentrations of dry matter, starch, crude protein and glycoalkaloids. Key findings reveal that total soluble phenols and anthocyanins contributed crucially to resistance expression in tuber tissue of coloured potato cultivars.