Evaluation of Andean potato cultivars as a source of dietary antioxidants

The Andean area of South America is the center of origin and diversity of the staple crop potato. Native Andean landraces represent a remarkable gene pool to exploit for the improvement of potato varieties. In the present study, the potential of the native germplasm was evaluated as a source of health-promoting compounds, and more particularly of dietary antioxidants. These phytochemicals receive an increasing interest due to their prospective effects on the prevention of various diseases such as cancers and cardiovascular diseases. In this study, a genetically diverse sample of 74 native potato cultivars (Solanum tuberosum L.) was field grown in 2004 in Huancayo (Peru, 3280 m above sea level). Using screening methods, we found a large variability of total phenolic, total carotenoid, and total vitamin C contents among the potato germplasm. The hydrophilic antioxidant capacity was also measured and was highly correlated with the total phenolics. On the basis of their contrasting contents, 23 potato cultivars were further selected for an in-depth analysis of their carotenoid, polyphenol, and tocopherol profiles. A wide range of antioxidant patterns could also be highlighted as well as cultivars of particular interest from a nutritional point of view. The stability of the ranking of cultivars across environment in terms of phenolic and carotenoid content was subsequently confirmed using 13 contrasted cultivars cultivated in 2005 in another highland environment (Huancani, Peru). This finding supports the fact that the potato genotype is the most determining factor of the observed variability. The effects of a drought stress on the dietary antioxidant contents were then investigated using a selection of five high antioxidant-contrasting cultivars. Drought-induced variations were complex with levels of antioxidants showing increase, decrease or remaining stable, depending on the genotype and the type of antioxidant considered. A gene expression analysis was finally used to gain an insight into the regulation of the production of the polyphenols. We demonstrated that the expression of 8 out of 13 polyphenol-related genes were coordinated and correlated with the polyphenol levels (both constitutive and drought-induced), supporting the fact that the production of polyphenols is, at least in part, controlled at the transcriptional level. Taken together, these results provide useful information concerning the health-promoting potential of the staple crop potato, and particularly of the native germplasm. We demonstrated the high diversity in potato tubers in terms of dietary antioxidants, identified genotypes with nutritionally interesting antioxidant composition, and highlighted their behavior under different environmental and drought stress conditions.(AGRO 3) -- UCL, 200