Volume 58 Number 2 Article 13 Pages: 98-107
Year 2004 Month 4
Title: Winter Hardiness Measurements on 15 New Apple Cultivars
Authors: H.A. Quamme and C.R. Hampson
Citation
Abstract:
Fifteen new cultivars from the 1995 NE-183 planting were evaluated for cold hardiness in November
and February for three consecutive winters, relative to 'Golden Delicious1 (winter tender) and 'Spartan'
(hardy). Pieces of dormant current season's shoots were frozen to a series of test temperatures from -20°C to -36°C in a programmable freezer.
In the final year, major scaffolds and trunks of certain
cultivars from the NE-183 trial, plus 'Royal Gala' and 'Summerland Mclntosh1, were also tested, to
establish the correlation between the hardiness of shoots and other parts of the tree.
Ratings of tissue
browning in the xylem and bark were used to assess injury after thawing.
The temperature of incipient
damage (TID), i.e. the warmest temperature at which a cultivar began to show injury, was obtained from
survival curves by non-linear regression.
TID varied significantly among cultivars, but not with sampling
season.
Overall, cultivars with shoots similar to 'Golden Delicious' in hardiness were: 'Arlet', 'Cameo',
'Orin1, 'Golden Supreme1 and 'Suncrisp.' 'Ginger Gold', 'GoldRush', 'Sunrise' and 'Braeburn' had TIDs
intermediate between 'Golden Delicious' and 'Spartan'. Clones with shoots as hardy as 'Spartan' were:
'Pristine', 'Fortune', 'Honeycrisp', 'Yataka', 'Fuji' and NY 75414-1. Trunks were less hardy than shoots
(had higher TID), and scaffolds tended to be intermediate.
For the NE-183 trees, the TID of shoots and
scaffolds, and the TID of trunks and scaffolds, from the same trees were significantly correlated.
The
TID for trunks and shoots was not correlated (R=0.24, p=0.29). This appeared to be attributable to
deviations in the hardiness among tissues of several cultivars, especially 'Fuji' and 'Fortune', which had
hardy shoots but tender trunks.
In contrast, the TID for trunks, scaffolds and shoots of 'Royal Gala' and
'Summerland Mclntosh' were all significantly and highly correlated (R>0.90). The development of
non-destructive methods to measure the hardiness of the trunk might improve the assessment of cultivar
hardiness.
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