FRAGANANAS: Wild Strawberries for improved cold adapation

Fragananas Peter Nick
Comparing the freezing response of sensitive and tolerant Wild Strawberries (image Dr. Adnan Kanbar).

What is the question? Strawberry (Fragaria × ananassa Duch.) is the cash crop of Egypt. Especially in winter, bevore the fruits from Southern Spain are available, the farmers in the Nile delta use this market niche. The project ventures to define genetic factors of frost tolerance. For this goal we use the genetic diversity of our native Wild Strawberry. In frame of the CWR Gene Bank this diversity had been collected all over Germany. By crossing with Sweet Charly, a variety relevant for Egypt, we want to improve the resilience against nocturnal freezing episodes as they occur also during the Egyptian winter. We also investigate, whether constrained irrigation can cause cold hardening.

What did we achieve? First, a method had to be developed to measure and, thus, compare, frost susceptibility. Since the transition between normal development and complete collapse is sharp, this was far from trivial. Eventually, a treatment with -6°C over two hours (mimicking a short frost night) turned out to discriminate between soft and tough genotypes. From 70 genotypes, 5 tough guys were identified. Now, we try to find out the cause for this freezing tolerance. For a especially tough specimen from the Northern Black Forest we found elevated levels of Cold Box Factor 4, a gene switch, known to play a role for freezing tolerance. This track will now be followed further. In cooperation with the Institute for Fruit and Vegetable of the Max-Rubner Institute we test now, how this is reflected in the metabolic compounds of leaves and fruits. The berries should not only be freezing tolerant, but also healthy and tasty.