Using sprouting behaviour to quantify physiological ageing of seed tubers of potato (Solanum tuberosum L.)

The physiological age of potato seed tubers evolves with chronological age, influenced by growth history and storage conditions. Effective quantification of physiological ageing requires a dynamic and flexible modelling approach. In this study, we conducted three cycles of field production and storage of seed tubers, using contrasting and widely grown cultivars. Different storage temperatures were employed as the sole treatment to introduce variation in the physiological age of the same cultivar. Throughout the storage seasons, periodic assessments of sprouting behaviour were conducted, both at the onset and at the end of a sprouting test. The total sprout dry weight per tuber produced in the sprouting test emerged as the best measure of seed tuber vigour, exhibiting cultivar-specific responses to storage temperatures. To capture these diverse sprouting behaviours, we devised a piecewise sprouting behaviour function. This is the first mathematical model that effectively describes the evolving sprouting patterns and provides biologically relevant parameters for the analysis of cultivar-specific sprouting trends. The temporal parameters of the function displayed sensitivity to storage temperature and year-to-year variation in growth conditions, highlighting distinct physiological phases. Consequently, the function facilitated insightful analysis of these key factors, enabling interpretation of underlying processes involved in the physiological ageing of potato seed tubers.