Freezing Tolerance of Tissue Cultured RubusPlants

Abstract

Tissue cultured ‘Perron Red,’ ‘September Red,’ and ‘Canby’ red raspberry, ‘Shawnee’ blackberry, and ‘Royalty’ purple raspberry plants 7 to 12 cm in height were subjected to artificial freezing tests. Apical meristems and roots of ‘Perron Red’ survived −8°C when whole plants were frozen at 1°C/hr; however, after seven days under mist in a greenhouse, plants subjected to −2°, −6°, or −8°C had less root regrowth than unfrozen controls. Shoot dry weight of plants subjected to temperatures below −2°C was reduced and root dry weight of plants exposed to −8°C was adversely affected when measured after 26 days in the greenhouse. When only shoots of whole plants were frozen, the lowest survival temperature (LST) for apical meristems of ‘Canby’ was −8°C, the LSTs of ‘Perron Red’, ‘September Red,’ and ‘Shawnee’ were all −12°C, and ‘Royalty’ remained uninjured at −14°C. Despite meristem survival, severe freezing injury to mature leaves of all cultivars occurred by −10°C. In another experiment, mefluidide (N-[2,4-dimethyl-5-[[(trifluoro-methyl)-sulfonyl]amino]-phenyl]acetamide) was applied to plants at 5 mg·l ⁻¹to determine if the growth regulator provided protection against low temperature injury. The LST of mefluidide-treated plants did not differ from the controls.