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  • Author or Editor: H. A. Quamme x
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High levels of decadienoate esters were found in the iso-octane soluble fraction extracted directly from pureed canned fruit of ‘Harvest Queen’, HW-606, ‘Bartlett’, 5 sports of ‘Bartlett’, ‘Surecrop’, and ‘Laxtons Progress’ pear (Pyrus communis L.). These cultivars, with the exception of ‘Surecrop’, had a Bartlett-like aroma. The decadienoate equivalents observed in 19 other cultivars ranged from none to one-half the high group. Higher levels of decadienoate esters were also detected by high pressure liquid chromatography (HPLC) in essences of canned fruit of ‘Bartlett’, ‘Harvest Queen’, and HW-606 with a Bartlett-like aroma than in canned fruit of 3 cultivars with aroma unlike ‘Bartlett’, including ‘Harrow Delight’, HW-607, and ‘Kieffer’. Cultivars with Bartlett-like aroma seem to be characterized by high decadienoate ester level, but high decadienoate ester levels are not necessarily indicative of Bartlett-like aroma. Decadienoate esters were not detected in essences extracted from actively growing or dormant shoots of ‘Bartlett’. Thus, early screening of seedlings for Bartlett-like aroma on basis of decadienoate extraction of the shoot or leaves cannot be effective.

Open Access
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A study to determine the freezing pattern in overwintering flower buds of peach (Prunus persica (L) Batsch) revealed that masses of ice formed in the flower bud scales and flower bud axis, but not the flower primordium. Water appeared to be withdrawn from the bud axis to freeze in preferred sites in the scales, but not from the flower primordium. The flower primordium appeared to survive to below −20°C by supercooling. Below −10°C the supercooled flower primordium could be induced to freeze by inoculating it with ice or excising it from the flower bud at the base. It is proposed that 2 barriers operate below −10°C to prevent external nucleation of the supercooled tissue, 1) the cuticle or epidermis which prevents nucleation by ice on the surface of the flower primordium, and 2) a dry region at the base which prevents an ice boundary from spreading into the flower primordium from the interior of the bud axis. The dry region is formed by water withdrawal into the scales during the initial stages of freezing. Below some critical temperature the ice boundary spreads through the dry region or the supercooled tissue nucleates spontaneously. The sudden explosive growth of ice kills the flower primordium, probably by intracellular freezing.

Open Access
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Abstract

In overwintering flower buds of ‘Redhaven’ peach [Prunus persica (L) Batsch], seasonal changes in the supercooling point were correlated significantly with seasonal changes in water content of the whole flower bud and its parts, the flower primordium within the flower bud and the vascular traces just below the flower primordium. Both the supercooling point and the water content of the whole flower bud and its parts were correlated significantly with the 2- and 5-day mean air temperature preceding collection. Controlled-temperature studies with ‘Siberian C’ and ‘Redhaven’ revealed that the water content of the flower primordium and vascular traces and not that of the whole flower bud was critical to the level of supercooling attained. Supercooling of the flower primordium appeared to be related directly to its water content. Water content of the vascular trace appeared to be important during the initial stages of freezing for preventing spread of the ice boundary into supercooled regions of the flower primordium. Water content of the 2 critical tissues appeared to be determined by migration from and to these tissues during freezing and thawing. During freezing, water was lost from the flower primordium and vascular traces by migration to the flower bud scales which appeared to act as an ice sink. After prolonged exposure to freezing outdoors, water was also lost to the exterior of the flower bud. After thawing, the flower primordium and vascular traces regained water content by transfer from the ice sinks within the flower bud and sources external to the flower bud. Loss of flower bud hardiness occurred during storage at 0°C for 10 days, which was not due to change in water content of the flower bud or its parts. The excised flower buds of the hardier ‘Siberian C’ supercooled to a lower temperature than excised flower buds of the less hardy ‘Redhaven’ at equivalent water content.

Open Access
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Abstract

Freezing injury to overwintering flower buds of apricot (Prunus armeniaca L.), European plum (P. domestica L.), Japanese plum (P. salicina Lindl.), peach (P. persica (L.) Batsch.), sweet cherry (P. avium L.) and sour cherry (P. cerasus L.) was found to be associated with an exothermic process detected on the time temperature profile. This exothermic process varied with seasonal fluctuations in the hardiness of 2 peach cultivars and was consistent with the hardiness of 5 cultivars tested on 3 dates during winter. No similar exotherm was detected in pear and apple. These results suggest that flower bud injury in some Prunus species was related to a specific event that involved freezing of a ‘bound’ or ‘supercooled’ fraction of water. This fraction of water remained unfrozen in the flower bud until the temperature fell below a critical level which in our studies was as low as -27°C. Exotherm flower bud hardiness in these fruit species.

Open Access

Abstract

Reductions in weed interference achieved through hand weeding or herbicides in a newly planted peach (Prunus persica (L.) Batsch) orchard led to increased summer growth and greater freezing resistance of bark and wood tissue in dormant scions. Controlled freezing tests for 2 winters following spring plantings indicated that bark and xylem tissues of scions from weed-free plots averaged 5.5° and 3.2°C more cold hardy, respectively, than those from unweeded plots.

Open Access
Authors: and

Abstract

The supercooling of flower primordia within dormant peach buds [Prunus persica (L.) Batsch.] is dependent on water migration from the base of the flower primordium to preferential sites of freezing in the flower bud scales and pith during the initial stages of freezing. The preferential freezing that occurs in the flower bud scales and pith does not appear to be caused by a difference in distribution of ice nucleators. The mean nucleation temperature of the flower bud increased with the amount of attached shoot, an indication that ice nucleation began in the shoot and spread into the flower bud. The flower primordium, however, appeared to have an intrinsic resistance to ice nucleation in comparison to other parts of the flower bud, which may be related to its lower water and osmotic potentials. The reduced osmotic potential of the flower primordium could be a consequence of significantly higher sucrose levels on a dry weight basis compared to that of the vascular tissue below the flower buds or that of the flower bud scales. A gradient in water potential between the xylem of the shoot and the flower bud also existed and may account for the recovery of water that is lost from the flower bud during freezing.

Open Access
Authors: and

Sensory evaluation methods were used to establish tentative guidelines for screening apple (Malus ×domestica Borkh.) breeding selections for four visual attributes. A panel of 42 regional consumers rated sample selections for fruit size on the 7-point “Just Right” (JR) scale, for fruit shape on a 7-point hedonic (liking) scale, and for the appearance of lenticels and stem bowl russet (SBR) on a 7-point affective (acceptability) scale. The panel most preferred a fruit about 7.5 cm in diameter. No evidence was found for range bias or for differences between yellow and red apples in size preference. Women and panelists over 55 years of age tended to prefer a slightly smaller apple. Panelists liked all the most common apple shapes. Lenticels generally became unacceptable when they exceeded 1.0 mm in diameter, but lenticel density was not related to acceptability. For red or yellow apples, SBR was acceptable on average, provided its maximum extent did not exceed about 55% of the fruit diameter. The panel's tolerance to SBR resembled that of a larger regional population, and their fruit size preferences resembled those reported elsewhere for European consumers. Similar methods could be used by other breeders to assess the preferences of their target consumer population.

Free access

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

Winter freeze events, identified by horticulturists to lower yields or kill trees (estimates vary by year from 1000 to >200,000 trees), have occurred in the Okanagan Valley of British Columbia 18 times in 94 years (1 in 5 years). To determine the association of winter temperatures and production, 72 years (1920–91) were separated into quartiles by level of production. Then, a maximum χ2 value was produced by a scanning iterative technique comparing each of the extreme quartiles with the combined mid-quartiles. A strong association was found between level of production and the low minimum temperatures in November, December, and February but not January. This result agrees with the historical records that indicate three winter-kill events occurred in November, five in December, one in January, and three in February during the same time period. Warm temperatures in September were associated with low production, indicating the possibility that warm temperatures at this time delay acclimation. Warm temperatures in January also were associated with low production, indicating a possible effect in hastening deacclimation.

Free access