The Use of a Bud Freezing Technique to Determine the Hardiness of 20 Grape Genotypes

摘要

Pencil thick canes (~8 mm) from 20 different grape cul-tivars were harvested at 2 different dates in the fall (October and Novem-be-r). The cultivars had previously been classified as hardy (group A), semi-hardy (group B) or tender (group C). Individual bud sections of the canes were placed in a refrigeration unit and subjected to sequential freezing temperatures of 19°F, 5°F, -8°F and -22°F (-7°C, -15°C, -22°C, and - 30°C) for 24 hours at each temperature. Samples were removed each day to evaluate the survival of buds. Results for the samples taken in October showed that almost 100% of the buds were killed once they were subjected to - 8°F (-22°C ) or colder. The critical temperature appeared to he 5°F (- 15°C), where there was a markeddifference in survival between the 3 groups of genotypes: percent mortality was 46%, 68% and 94% for groups A, B, and C, respectively, In November, most of the hardy cultivars showed little adverse effects at -8°F (-22°C), whereas the tender cultivarssuffered the most injury with percent mortality of 2.5% and 83%, respectively.