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The severity of chilling injury in zucchini squash stored at 5C than transferred to 20C was reduced with the prestorage treatment of 42C hot water for 30 min. The chilling injury was further reduced when squash were preconditioned at 15C for 2 days after hot water treatment but before the 5C storage. Squash stored at 15C did not develop any symptoms of chilling injury. However, weight loss was most severe in squash stored at 15C. Squash kept at 5C had the least weight loss during the 2-week storage. Weight losses were comparable in squash treated or not treated with hot water. Analysis of polyamines in squash preconditioned with high and low temperatures is in progress. The effect of hot water treatment on the changes of putrescine, spermidine, and spermine and its implication in reducing chilling injury will be discussed.

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High-chilling pear cv. Shinseiki (Pyrus serotina Rehd.) were used to evaluate the cultivation potentiality at warm area via the decrement of supraoptimum temperature damage and the escape from dormancy. Several experimental results were obtained as follows: the media prepared by combination of peat and bark compost (1:1 in volume) inside nonwoven bag was lower in temperature than other media; both of the temperature of leaf surface and media decreased more than 2′C at noon by 25% shading favoring the CO2 exchange in the daytime; the foliage application of Aminofol increased leaf thickness and chlorophyll content; and BA or PP-333 treatment enhanced lateral buds development during the supraoptimum temperature period of summer, etc. An integrated management based on these results helped the 1-year old container-grown Shinseiki pear trees over-summer. The experimental trees were then forced to budbreak and flower by application of cyanamide in October. Eventually, the fruits were harvested in March. These results suggested that the production of high-chilling pears in warm area was technically feasible.

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Abstract

The effect of exposure of small peach plants (Prunus persica (L.) Batsch cvs. Redhaven and Redskin) to daily fluctuating temperatures (16 hours low: 8 hours high) of 6-15°, 6-18°, 6-21° and 6-24°C was examined in comparison with continuous chilling at 4° and a non-chilled control. Even though all chilling treatments received the same amount of chilling (weighted chilling hours), good leaf bud break was obtained only in the continuous 4°, 6-15° and 6-18° treatments. No lateral leaf buds opened in the 6-21°, 6-24° or the non-chilJed controls of both cultivars. The 6-15° temperature regime was more efficient than continuous chilling in breaking bud rest on a weighted chilling hour basis. ‘Redskin’ lateral buds were shown to have a higher chilling requirement than ‘Redhaven’. Terminal buds especially of ‘Redhaven’ showed a very low chilling requirement. Treating plants with 50 or 150 mg/liter GA3 slightly advanced bud break but did not affect the level of sprouting.

Open Access

Pear growing in subtropics began with the advent of low-chill pears, but their fruit quality is inferior to high-chill European/Oriental pears. Thus, the best way to produce high-chill pears in subtropics is by topworking them on the low-chill pears. To attain this, pruned wood with spurs of `Doyenne du Comice' (DCP) and `Victoria pear' (VP) cultivars were collected in January from Hort Expt Center Chaubatia, India (6825'ASL), and tongue grafted on low-chill `Pant Pear-18' (PP18). The grafting was at different heights on trees using 25-cm and 1-m long stocks on Tatura trellis-trained PP18 trees at the Hort. Research Center, Pantnagar (760' ASL). More than 90% grafts succeeded and both DCP and VP produced high quality fruits, but DCP grafts had an edge over VP scions. Both high-chill cultivars topworked on 25-cm stocks had better grafting success (95%) than the scions topworked on 1-m stocks (92%). The increase in topworking heights on stock trees reduced the floral spur numbers in both scions grafted on 25-cm stocks, but not on the scions grafted on 1-m stocks. With the incremental height of topworking irrespective of the length of stocks, the percentage of fruit set was curtailed by 28% and 12% for the DCP and VP scions, respectively. Irrespective of the topworking heights and stock lengths, the fruit yield for DCP (12.5 lbs/tree) was markedly higher than for VP (7.9 lbs/tree). Fruit quality attributes judged by organoleptic testing, TSS, total sugars, acidity, and ascorbic acid, were better for both DCP and VP than for PP18 and other local pear cultivars. The reuse of previous year's scions topworked even after artificial chilling and/or GA3 application to supplement chilling exhibited no fruiting advantage over the grafting using fresh scions.

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Crops with origins in tropics and subtropics undergo physiological injury when subjected to nonfreezing temperatures below 12°C. Application of heat and chemical shocks to tissue prior to chilling induces chilling tolerance. This study was undertaken to investigate the effects of low oxygen and high carbon dioxide atmospheres on subsequent chilling tolerance. Cucumber seedlings (Cucumis sativus L., cv. Poinsett 76) with radicles 8 to 12 mm long were subjected to 0% to 21% oxygen and/or 0% to 20% CO2 atmospheres for 0 to 72 hr at 2.5 or 15°C. After chilling, they were placed at 25°C for three additional days. Radicle growth was used to assess chilling injury. Modification of the individual germination plates was necessary to ensure seedling exposure to the desired atmospheres. Chilling injury was reduced by exposure to oxygen levels below 1% and to carbon dioxide levels above 5%. Effects of brief exposures were small in comparison to prolonged exposures during chilling. Seed to seed variability was high and obscured some results. The effects of the various atmospheres were greater with the less vigorous seedlings.

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207 ORAL SESSION 54 (Abstr. 478–482) Cross-commodity: Chilling Stress

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The fungicides thiabendazole (TBZ) or imazalil were applied at 1 g·liter-1 at 24 or 53C to `Marsh' and `Redblush' grapefruit (Citrus paradis i Macf.) to reduce fruit susceptibility to chilling injury (CI) and decay. There was more CI and decay on `Marsh' grapefruit than on `Redblush'. CI was found to be lower in grapefruit that had been dipped at 53C than at 24C. CI was higher after water dips without fungicide. Imazalil was found to be more effective in reducing CI than TBZ. Fungicides reduced decay at both temperatures, and imazalil was better than TBZ. Results of this study confirm the benefits of high-temperature fungicide treatments for maintaining grapefruit quality and indicate some benefits of high-temperature fungicide treatments for reducing CI.

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The dormancy of Japanese pear (Pyrus pyrifolia Nakai) floral buds was broken by prolonged chilling or short-term high-temperature treatment (45 °C for 4 hours). Changes in the protein profiles of the floral buds were studied using two-dimensional electrophoretic analysis (2-DE). The quantities of nine cold-induced proteins (CIPs) increased in the floral buds with increases in chill unit (CU) value, but did not change rapidly when bud dormancy was near completion. When dormancy of floral buds was broken by high-temperature treatment, nine heat-shock proteins (HSPs) accumulated. These HSPs were distinct from the CIPs. The isoelectric point of the 19-kDa CIP shifted to the basic side by high-temperature treatment as well as by chilling. These results suggest that the 19-kDa protein may be a usable marker to measure the degree of bud dormancy in Japanese pear.

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Abstract

Leaf bud break of ‘Redhaven’ and ‘Redskin’ peach (Prunus persica (L.) Batsch) following exposure of plants to temperature cycles of 1, 3, 6 and 9 days was examined. During each cycle the plants were exposed to 4°–6°C for 2/3 of the cycle length and 24° for the remaining 1/3 with all cycles repeated until the plants were exposed to a designated number of chilling hours. Thus, all plants within each treatment were exposed equally (in total) to chilling and heat. No lateral bud (LB) break occurred with ‘Redskin’ in the 1-day cycle, a low level was obtained in the 3-day cycle and good bud break occurred in the continuous chilling control and the 6 and 9 day cycles. With ‘Redhaven’ no LB break was evident in the 1 day cycle while the 3, 6, and 9 day cycles responded similar to the continuous chilling control. From these data it was concluded that chilling (4°-6°) accumulated during the 20 to 40 hrs prior to the onset of high temperature was susceptible to high temperature negation.

Open Access

‘lucía myrtea’ and ‘victoria myrtea’ are early-season cultivars of Japanese plum ( Prunus salicina Lindl.) typology, both characterized by their low chilling requirements, so their adaptation is ideal for warm growing areas in the current context

Open Access