Flowering physiology and cold resistance of Potentilla palustris (L.) Scop., a wild relative of the strawberry

Abstract

Environmental control of growth and flowering and the freezing tolerance of two Norwegian populations of Potentilla palustris (L.) Scop. were studied under controlled environment conditions. Under short day (SD; 10 h) conditions, the plants ceased growing and entered a semi-dormant state at temperatures ranging from 9° - 21°C, while under long day (LD; 24 h) conditions, growth was highly temperature-dependent. At 21°C, the plants continued to grow and remained vegetative in LD for at least 16 weeks. Flowering was induced at all temperatures in SD, while in LD at lower temperatures only.The critical photoperiods for floral induction at 21°C were 18 h and 20 h for the South Norwegian and the North Norwegian population, respectively. However, the initiation of floral primordia required a transition from SD to LD conditions. Three weeks of exposure to SD at an intermediate temperature was sufficient for floral induction in both cultivars, but flowering increased with increasing exposure, up to 7 weeks. SD-induced plants, that had ceased growing, resumed normal growth when returned to LD and high temperature in the absence of chilling, but only a few plants flowered without chilling. High-latitude P. palustris plants survived freezing at temperatures down to -30°C, whereas even the hardiest populations of the related wood strawberry (Fragaria vesca L.) were killed at temperatures below -10°C.We conclude that, considering the relative ease with which the frost-susceptible garden strawberry can be crossed with the frost-resistant P. palustris, the latter represents a promising progenitor for breeding new, cold-resistant strawberry cultivars.