Zinc uptake and partitioning in two potato cultivars: implications for biofortification

Aims Zinc biofortification through agronomic and/or genetic approaches is one of the strategies to enrich food with this essential element to fulfil nutritional requirements in poor diets. This study aimed to unravel the physiological basis of differential tuber-Zn concentration between potato cultivars and to identify the major source(s) of Zn to the tubers. Methods Two potato cultivars, accumulating high (Lady Rosetta) and low (Cara) tuber-Zn, were evaluated and the patterns of biomass and Zn accumulation between organs assessed over the growth period. Furthermore, Zn partition in reciprocal grafted plants and in sixteen F 1 genotypes following a cross between those cultivars was assessed at harvest. Results The cultivars differed in Zn-concentration, Zn-content and biomass partitioning between organs, although total plant-Zn content was comparable (4.7 and 5.1 mg Zn/plant for Cara and Lady Rosetta, respectively). At harvest the relative amount of Zn retained in roots, stems, leaves and tubers was 2 %,25 %,5 % and 68 % for Cara and 1 %,17 %,5 % and 77 % for Lady Rosetta. The differential tuber-Zn was associated with internal Zn distribution between shoots and tubers. Lady Rosetta translocated higher amounts of Zn to the tubers while Cara accumulated relatively more Zn in the stems associated with higher stem biomass. Remobilization of Zn from leaves and stems, and continuous root to xylem-phloem transfers during tuber bulking were the major sources of Zn supply to the tubers. Conclusions This study suggests that the potato stem plays an important role in regulating Zn distribution and also as a site for Zn deposition.