In our experiments, we examined the effect of six different durations and degrees of heat and cold shock treatments on the tuber dormancy period of three different Hungarian potato cultivars of different basic tuber dormancy period (Balaton rose, Botond, Demon). Examinations were performed for three years in three consecutive storage periods. To express the length of the tuber dormancy period, the results were also expressed in terms of the amount of cumulative heat required for the tuber dormancy period and the number of days elapsed. Based on the obtained results, the performed treatments significantly affected the dormancy period of the examined varieties. Of the treatments used, changing storage temperatures shortened the dormancy period the most. More specifically, warm pretreatment (heat shock, 2 weeks at 35 °C) was significantly more effective than cold pretreatment (cold shock, 2 weeks at 5 °C) had a significant effect. Short-term high-temperature treatment also reduced dormancy to a lesser extent. However, persistent high-temperature treatment increased dormancy and resulted in prolonged germination. The physiological reason for this phenomenon may be forced dormancy, where the activity of the dividing tissue is no longer blocked by internal physiological factors but by external environmental factors (Suttle 2007). The tubers received the amount of heat needed to end the dormancy period, but the prevailing environmental conditions were not favorable for germination (van Ittesrum 1992). At low storage temperatures, we observed that in our study, cultivars with a longer basic tuber dormancy period also had a longer tuber dormancy period as a result of treatment, i.e. the order of the cultivars remained unchanged. However, this has changed as a result of high temperature treatments, as there were cases when the order of different varieties changed.

We found significant differences between each crop year. Consequently, the weather of the growing season and the amount of heat absorbed by the mother plants had an effect on the basic dormancy of the varieties and through this also affected the effectiveness of treatments.

Our study results supported the findings of other researchers in many cases (e.g., short-term low-temperature treatment shortens the dormancy period; alternating temperature storage shortens the dormancy period more than constant storage temperature; warm pretreatment is more effective than cold pretreatment). In several cases, however, different conclusions were made. In our case, the permanent heat effect of around 30 °C increased the dormancy period and heat shock treatment (35 °C) did not lead to the immediate ending of the dormancy period.

The results of the literature on the study of the dormancy period of potato tubers have led to a number of generalizable conclusions that we have confirmed. In addition, the different empirical results emphasized the strong genetic specificity of the studied trait, the dependence of the genotype, and the different reaction of the varieties to environmental factors. In view of the above findings, we consider it necessary to perform a similar series of experiments for each new variety or candidate variety in order to determine the optimal storage conditions appropriate to the storage purpose.

Keywords: Solanum tuberosum, controlling the dormancy period, storage conditions