Evaluation of three methods to assess winter hardiness of strawberry genotypes

摘要

In northern regions, winter injury is a frequent problem in strawberry (Fragaria ananassa) production. Controlled freezing tests provide an option for screening of winter survival potential in different genotypes. In this study, winter hardiness ofstrawberry genotypes was evaluated by three low-temperature procedures: an artificial hardening-dehardening-rehardening programme accompanied by freezing tests, prolonged freezing test, and laboratory cold hardiness measurements of field-grown plants. Rooted runner cuttings of five June-bearing strawberry cultivars (Senga Sengana, Korona, Bounty, Honeoye and Jonsok) and three new selections (91054019 (Hella x Glima), 91062123 (Hella x Redgauntlet) and 91110007 (Bogota x Rubino)) were tested in the course of two years (1998-99 and 1999-2000) in Helsinki, Finland. Relative winter hardiness of the genotypes could not be predicted by the hardening-dehardening-rehardening programme employed in the present study. Prolonged freezing at -6degC yielded promisingresults, whereas storage at -4 and -8degC failed in discrimination between genotypes. Field-grown plants were sampled for cold hardiness measurements in January, March and April. The genotypes were best differentiated in January, at a fully acclimatized state. The results indicate that strawberry winter hardiness can be evaluated by testing differences in the ability to survive lengthy exposure to sub-lethal low temperatures, or by applying conventional freezing tests to measure cold hardiness in different genotypes after field acclimatization.