ISHS Acta Horticulturae 565: VI International Symposium on Temperate Fruit Growing in the Tropics and Subtropics
THE EFFECT OF LOW TEMPERATURES ON THE DORMANCY OF THREE APPLE CULTIVARS IN THE PO VALLEY |
| Author: | G.A. Finetto |
| Keywords: | budbreak, bud development index, chilling requirement, dormancy |
| Abstract:
The effect of the low temperatures (below 0°C) on the dormancy of temperate fruits is not well understood. This factor is particularly important for cultivation of temperate fruit in the highlands of the tropical and sub-tropical zones. Mid- and high-chilling apple cultivars (Summered, Golden Delicious and Morgendurf) planted in 1985 were studied during the fall from 1996 to 1999. Thirty samples of one-year twigs and shoots with spurs were taken from the three cultivars in the field on the first days of October, November and December. The materials were held in refrigerator at 0°C, -5°C, and 12 hours at -5°C and 12 hours at 0°C (-5°/0°C). After 21 days of treatments the shoots were transferred to a growth chamber at 21°C. The number of opened buds (apical and lateral) was recorded and expressed both a percentage of the total and bud development stage index. The data were compared with those of the shoots collected from the field under the winter outdoors temperatures from October up to the end of dormancy (January). Field temperatures were recorded and used to calculate chilling accumulation using Richardson’s model. The buds of the mid-chilling requirement cultivars (Summered and Golden Delicious) treated at 0°C and at -5°/0°C overcame the dormancy after 30 days. It took 30-35 days for budbreak in the high chilling cultivar (Morgendurf), and more than 35 days at -5°C.These results indicate that the low temperatures promoted the break of endo-dormancy in the cultivars examined, but the responses were related to phenological stage and type of the buds when the cold treatment were applied. Finally, models designed to estimate chilling requirements should consider the effect of cold temperature during the dormancy. | |
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