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  • Author or Editor: G. A. Spearman x
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Abstract

‘Harvest Queen’ and ‘Harrow Delight’ are high-quality pear cultivars introduced for early fresh-market and home garden use. At Harrow, ‘Harvest Queen’ ripens during the 3rd week of August, one week before ‘Bartlett’, and ‘Harrow Delight’ ripens during the 2nd week of August, 2 weeks before ‘Bartlett’ (Table 1). Both cultivars are resistant to fire blight caused by Erwinia amylovora (Burr.) Winsl. et al., and are adapted to conditions in southern Ontario.

Open Access

Abstract

A method of exotherm analysis is described for determining the cold hardiness of dormant peach flower buds (Prunus persica (L.) Batsch). Twig pieces with intact flower buds were placed into thermos bottles and cooled at a constant rate in a programmed cold chamber. A thermocouple was inserted in the node of each twig piece to measure the temperature at which sudden heat release occurred. Thermocouples connected in series made it possible to record exotherms of 5 twig pieces from a cultivar on a single channel of a multipoint recorder. The exotherm method was compared to the LT50 method (the temperature at which 50% of the flower buds are killed) using 10 cultivars on one collection date. The mean temperatures at which the exotherms were initiated were significantly correlated with the LT50 (r = +.880). In addition, the mean temperatures at which exotherms were initiated and the LT50 for these cultivars were significantly correlated with the percentage of flower bud mortality averaged over 4 winters (r = −.667 and −.797, respectively). The exotherm method gives a direct measurement of the temperature at which peach flower buds are killed and offers an opportunity for studying the cold hardiness of individual flower buds not possible with other methods.

Open Access