Yield potential of seed potatoes grown at different latitudes in Norway

In a four-year field study (2000–2003), seed potatoes of three Norwegian cultivars (Troll, Beate and Peik) from a single source were produced at four sites ranging from 59° to 69°N, followed by similar winter storage. Physiological age was measured early and late in the storage period and field performance in the next season was studied at a northern site (short, cool season) and a southern site (relatively longer, warmer season). With respect to vigour, growth and yields, the results showed no significant superiority of seed from any latitude within Norwegian conditions, although some differences occurred among the seed origins. The physiological age, based on measurements of incubation periods, was clearly different early and late in the storage period and varied between cultivars. However, no systematic variation was found between latitudes. A physiological age index (Caldiz et al., 2001) was calculated from a formula using a combination of incubation periods and chronological age from haulm-k...