Effects of organic versus conventional cultivation system on nutritional quality of "early" potato tubers

Consumer demand for organic potatoes has been increasing in Europe, relying on the perception that their nutritional quality is superior to that of the conventionally grown equivalent. The improved qualitative value of organic vs. conventional produce, however, has not been ascertained. Further knowledge about tuber quality of new potato genotypes considered suitable for organic farming could be important. The effect of the cultivation system on nutritional quality (dry matter, ascorbic acid and total phenolics content, titratable acidity, antioxidant activity) of early potato tubers was explored in a field trial conducted during two-season in Sicily (southern Italy) and involving five yellow-fleshed genotypes ('Arinda', 'Bionica', 'Ditta', 'Marabel' and a breeding clone ISCI 4F88 suitable for organic cultivation). The organic cultivation system produced tubers exhibiting, averaged across genotypes and seasons, lower titratable acidity (1.64 vs. 2.09 g citric acid kg-1 dry weight), ascorbic acid content (0.14 vs. 0.18 g kg-1 fresh weight) and antioxidant activity (42 vs. 56% DPPH reduction), but higher dry matter content (197 vs. 186 g kg-1 fresh weight) and total phenolics content (3.50 vs. 2.32 g GAE kg-1 dry weight). Among the genotypes, 'Ditta' and ISCI 4F88 under organic showed the highest tuber dry matter and total phenolics contents, whereas 'Arinda' the highest ascorbic acid content and antioxidant activity. Even if the response of organic cultivation on nutritional quality also depended upon seasonal conditions, cultivar choice plays a key role in optimizing this production system, highlighting the importance of breeding programs.