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Wendy S. Higgins and Dennis P. Stimart

Lilium longiflorum Thunb. `Ace' bulblets generated in vitro at 25 or 30C were stored at 4C for O, 1, 2, 4, or 6 weeks after removal from culture and before planting to ascertain the effects of in vitro generation temperature and post-in vitro cold storage duration on bulblet growth responses during 36 weeks of greenhouse growth. Increasing post-in vitro storage duration decreased the number of days to first leaf emergence and percentage of plants producing shoots within 36 weeks, but increased the number of days to shoot emergence and anthesis, leaf number, and flower bud number. The length of time required for bulblet development from planting to shoot emergence was affected by storage duration more than periods from shoot emergence to visible bud and anthesis. It is feasible to produce high-quality L. longiflorum pot plants from in vitro-produced bulblets.

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R. Porat, B. Weiss, L. Cohen, A. Daus, and E. Cohen

`Oroblanco' is an early-maturing pummelo-grapefruit hybrid (Citrus grandis × C. paradisi). The fruit of this cultivar are usually picked in October and are marketed while their peel color is still green. However, during long-term storage, the fruit turns yellow, and loses much of their commercial value. In a previous study, we found that application of gibberellic acid and low storage temperatures of 2 °C (35.6 °F) markedly reduced the rate of degreening. However, `Oroblanco' fruit are sensitive to chilling injuries, and thus could not be stored at 2 °C for long periods. In the present study, we examined the possible application of intermittent warming (IW) and temperature conditioning (TC) treatments, in order to retain the green fruit color during long-term cold storage but without enhancing the development of chilling injuries. It was found, that following storage at 2 °C, either with or without IW and TC, the fruit retained green color up to 16 weeks, whereas at 11 °C (51.8 °F) fruit turned yellow after 8 weeks. However, untreated fruit held continuously at 2 °C developed 40, 51, and 68% chilling injuries after 8, 12, and 16 weeks, respectively. IW (storage at cycles of 3 weeks at 2 °C + 1 week at 11 °C) reduced the amount of chilling injuries to only 5, 7 and 11% after the same periods of time, respectively. TC [a pre-storage treatment for 7 days at 16 °C (60.8 °F) before continuous storage at 2 °C] effectively reduced the development of chilling injuries to only 5% after 8 weeks of storage, but was ineffective in reducing chilling damage after longer storage periods. Because chilling damaged fruit is prone to decay, the IW and TC treatments also reduced the incidence of decay development during storage. The IW and TC treatments did not affect juice total soluble solids and acid percentages, but did affect fruit taste and the amounts of off-flavor volatiles emitted from the juice. Taste panels indicated that the taste score of untreated control fruit stored at 11 °C gradually decreased during long-term storage, and that this decrease was more severe in chilling damaged fruit stored continuously at 2 °C. The taste of IW-treated fruit remained acceptable even after 16 weeks of storage, and TC-treated fruit remained acceptable for up to 12 weeks. Fruit taste scores were inversely correlated with the concentrations of ethanol and acetaldehyde detected in the juice headspace.

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Karen L.B. Gast and Melinda McMillan

Peony flowers are among the few fresh-cut flowers that can be stored dry at cold temperatures for weeks and still produce a viable product for the marketplace. Devising new ways to extend that storage period could open new markets for peony growers. In the northern hemisphere, more peonies could be available for summer weddings, and in the southern hemisphere, red peonies could be used for Valentine's Day. Being able to control and extend the vaselife of peony flowers could also be useful for companies that freeze-dry peonies. Their production is limited by the length of their processing cycle and the size of their freeze dryer. Being able to extend their production season could make them more profitable. Three treatments were applied to peony flowers harvested in the colored bud stage before flowers where placed in cold storage, 2°C. An untreated control was included. Flowers were removed from storage every 2 weeks for 14 weeks. Vaselife and fresh weights were evaluated. Total nonstructural carbohydrate levels of the petals, leaves, and stems of the flowers are to be analyzed. Preliminary analysis of the data shows some treatment differences.

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Roger Romani, Rolf Puschmann, Jack Finch, and James Beutel

Abstract

Application of 400 ppm aminoethoxyvinylglycine (AVG) to pear trees 6 and 2 weeks before harvest resulted in marked but variable inhibition of postharvest ripening at 20°C. AVG amplified the usual nonuniformity in the initiation of ripening exhibited by freshly harvested fruit. Prolonged storage of the fruit at 0 to 2°c counteracted the inhibitory effects with resultant rapid and uniform ripening upon transfer to 20°c. However, a physiological nonuniformity as reflected by wide differences in internal C2H4 concentration persisted well beyond the time when threshold levels for the initiation of ripening had been reached by all fruit. Probable relationships between AVG effects, cold storage, and C2H4 are illustrated diagrammatically.

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Rajeev Arora, Michael Wisniewski, and Lisa J. Rowland

Seasonal pattern of cold tolerance and proteins were studied in the leaves of sibling deciduous and evergreen peach (Prunus persica). In contrast to deciduous peach that undergoes endodormancy in fall, evergreen peach does not (leaves are retained and shoot tips elongate under favorable conditions) (Arora et al., Plant Physiol. 99:1562-1568). Cold tolerance (LT50) was assessed using electrolyte leakage method. Proteins were separated by SDS-PAGE. Electroblots were probed with anti-dehydrin (Dr. T. Close) and anti-19 kD, peach bark storage protein (BSP) antibodies. LT50 of leaves successively increased from about -7C (18 Aug.) to -15C and -11.5C (23 Oct.) in deciduous and evergreen genotypes, respectively. The most apparent change in the protein profiles was the accumulation of a 60-kD protein during cold acclimation in the leaves of deciduous trees; however, it did not change significantly in evergreen peach. Immunoblots indicate that 60-kD protein is a dehydrin protein. PAGE and immunoblots indicated that 19-kD BSP disappeared progressively during summer through fall in the leaves of deciduous peach, but accumulated to large amounts in bark tissues. Similar inverse relationship for its accumulation in leaf vs. bark tissue was not evident in evergreen peach. Results indicate that BSP expression may be regulated by altered source/sink relationship.

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Anil P. Ranwala and William B. Miller

Our previous research has demonstrated preventive effects of foliar sprays of growth regulators containing GA4+7 (ProVide or Promalin) on cold storage-induced leaf yellowing and abscission in `Stargazer' hybrid lilies. Further research was conducted to investigate the effective concentrations of Promalin and appropriate timing of promalin sprays. Lilies at “puffy bud” stage were sprayed with promalin at concentrations of 10, 25, 50 or 100 ppm (each GA4+7 and BA) just before placing them at 4 °C for 2 weeks in darkness. Promalin concentrations of 25 ppm or above completely prevented cold storage-induced leaf yellowing occurring during the poststorage evaluation phase in a simulated consumer environment, whereas 10 ppm sprays only partially prevented it. Foliar spray of Promalin (100 ppm each GA4+7 and BA) just before storage at 4 °C for 2 weeks was compared with spraying 2 or 4 weeks before cold storage. While spraying 2 weeks before storage prevented leaf yellowing to the same extent observed in plants sprayed just before cold storage, spraying 4 weeks before storage had very little preventive effect on leaf yellowing. To investigate the effectiveness of promalin sprays with different cold storage durations, puffy-bud stage plants were stored at 4 °C for 1, 2, 3, 4, or 5 weeks in darkness with or without promalin sprays (100 ppm each GA4+7 and BA) before storage. Longer cold storage durations increased the severity of leaf yellowing occurring during poststorage phase. Although promalin was able to prevent leaf yellowing completely up to 2 weeks of cold storage, beyond 3 weeks of cold-storage, effectiveness of promalin diminished with no apparent preventive effect on plants stored for 5 weeks.

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Rajeev Arora, Michael Wisniewski, and Lisa J. Rowland

Seasonal changes in cold tolerance and proteins were studied in the leaves of sibling deciduous and evergreen peach [Prunus persica (L.) Batsch]. Freezing tolerance [defined as the subzero temperature at which 50% injury occurred (LT50)] was assessed using electrolyte leakage. Proteins were separated by sodium dodecyl sulfate polyacrylamide-gel electrophoresis. Electroblots were probed with anti-dehydrin and anti-19-kD peach bark storage protein (BSP) antibodies. Leaf LT50 decreased successively from -5.8 °C on 18 Aug. to -10.3 °C in the evergreen genotype and from -7.0 °C to -15.0 °C in the deciduous genotype by 14 Oct. Protein profiles and immunoblots indicated the accumulation of a 60- and 30-kD protein during cold acclimation in the leaves of deciduous trees; however, levels of these proteins did not change significantly in the evergreen trees. Immunoblots indicate that the 60-kD protein is a dehydrin-like protein. Gel-electrophoresis and immunoblots also indicated that the 19-kD BSP progressively disappeared from summer through fall in leaves of deciduous peach but accumulated to a high level in bark tissues. A similar inverse relationship was not evident in evergreen peach.

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Eduardo Olate, Doris Ly, George Elliott, and Mark Bridgen

Two butterfly-type cultivars of Alstroemeria were used to evaluate the effect of different dates of propagation and cold storage techniques on the growth and flowering of potted plants. The cultivars used were `Patricia Lynn' and FL-101. Plants were propagated during four different dates of 1997 (weeks 39, 41, 43, and 47) in large nursery pots (3.8 L) or in small nursery pots (1.4 L). Following division, all plants were grown for 4 weeks. After this period of establishment, plants in the large nursery pots were transferred directly to the final growing greenhouse (16 °C nights) and plants in the small pots were refrigerated at 4 °C for 8, 6, 4, or 0 weeks with either complete light or complete dark conditions. Once the cold treatment was accomplished, all plants were transferred on the same date to large nursery pots for finishing with those plants that had been initially propagated in large pots. All plants were cut back on week 3 of 1998. Plants were evaluated for date of harvest, visual evaluation, fresh aerial weight, number and length of flowering stems, and number of florets per flowering stem. Refrigerated treatments delayed the time of flowering when compared to plants that were grown with no refrigeration. Fresh weight and stem length values of plants that were not refrigerated were less than or equal to those of plants that were refrigerated, with the exception of plants that was propagated on week 47. In addition, the number of flowering stems that were produced from plants that were refrigerated was either greater than or the same as plants that were not refrigerated. The presence or absence of light during refrigeration had no effect on subsequent plant growth and development. There were no differences observed among treatments for visual evaluation and number of florets produced per inflorescence. This research demonstrated that potted Alstroemeria plants can be propagated early and stored under cold conditions without these procedures affecting final plant performance, but the process will affect the scheduling of the crop.

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Victor Voth and R. S. Bringhurst

Abstract

Eight non-everbearing California strawberry cultivars were evaluated under the standard winter planting system (October-November) in comparisons involving differentials in plant harvest and transplanting dates and comparing approximately 30, 15 and 0 days of cold storage conditioning at Santa Ana, a relatively warm-winter south coastal California site. The varieties differed greatly in performance and the results were consistent with that which is known of their varying performance under commercial conditions. ‘Sequoia’ was almost an ideal performer but the fruit lacks firmness. Photoperiod is important in governing the reproductive response under this planting system since the duration of the fruiting period for a given variety was directly associated with how long the plant had grown under short days. However, chilling appeared to be the dominant factor governing acceptable performance in all varieties except ‘Sequoia’. ‘Sequoia’ performed satisfactorily over the entire range of treatments and although it responded to chilling, apparently it has a short rest period. Of the other varieties that are of great economic importance in California, ‘Fresno’ and ‘Shasta’ evidently have relatively long rest periods and cannot be manipulated satisfactorily under the winter planting system whereas ‘Tioga’ is intermediate and responds favorably to manipulation.

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Wilawan Kumpoun, Takashi Nishizawa, Yoshie Motomura, Tanidchaya Puthmee, and Toshiyuki Aikawa

conditions because the antioxidant capacities of mango fruit also decrease during cold storage ( Ding et al., 2007 ; Miguel et al., 2011 ; Shivashankara et al., 2004 ), which may result in the disturbance of physiological functions in the cell membranes