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Natalia R. Dolce, Luis A. Mroginski, and Hebe Y. Rey

the significance of mean differences was determined using Tukey's multiple comparison test ( P < 0.05). Percentage data were transformed using the square root for the cold storage experiment and the transformation log(2+%germination) for the different

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Mariateresa Cardarelli, Youssef Rouphael, Francesco Saccardo, and Giuseppe Colla

A research project was conducted at the University of Tuscia, Viterbo (central Italy), to set up a vegetative propagation system for producing diseasefree artichoke transplants (Cynara cardunculus var. scolymus) of the Romanesco type (cultivar C3). The system included the following steps: 1) micropropagated plantlets were grown in a soilless culture year-round in greenhouse conditions, starting at the end of August; 2) stock plants were periodically treated with a chemical growth regulator [6-benzylamino purine (BA)] and then cut back at the collar level to promote offshoot production; 3) offshoots were periodically harvested and cold stored; and 4) cuttings were rooted at the end of spring under conditions of high humidity in multi-pack trays so as to be ready for summer transplanting. Results showed that the foliar application of BA to the stock plants increased the offshoot number quadratically to 200 mg·L-1. The rooting percentages of cuttings and root growth were enhanced by raising the cutting weight class (30-45 g) and by the application of naphthaleneacetic acid (NAA) to the cutting root zone at a rate of 2000 mg·L-1. The percent rotten cuttings increased as the 2 °C cold-storage time increased from 30 to 150 days. Similarly, the percentage of rooting and root growth decreased approximately from 60 to 150 days.

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Barbara M. Reed

Medium-term in vitro cold storage of Rubus germplasm was investigated using various temperatures, photoperiods, and storage containers. Shoot cultures of several Rubus taxa were grown either in tissue-culture hags or 20 × 150-mm glass tubes. Cultures stored at 10C in darkness were in poor condition after 6 months. Overall survival and condition ratings were significantly better for bags than tubes when cultures were kept at 4C. Contamination was present in 14% of the tubes, but only 3% of the bags. Addition of a 12-hour photoperiod to 4C storage significantly improved both condition ratings and survival percentages of many individual genotypes. Evaluation of the 250-accession germplasm collection after 12 months at 4C (dark) showed 92% of accessions in bags and 85% in tubes in suitable condition to remain in storage. Storage of cold-sensitive genotypes in tissue-culture bags at 25C with a 16-hour daylength was extended to 9 months when the MS-medium nitrogen level was reduced to 25% of standard concentration. Survival of `Mandarin' raspberry stored for 9 months improved from 40% at 4C (100% N) to 90% at 25C (25% N). Results of these studies suggest that most Rubus germplasm can be stored safely at 4C with 12 hours of light. Plastic tissue-culture bags are preferred over tubes due to higher survival and lower contamination rates. Storage at 25C on reduced-nitrogen medium is an alternative method for cold-sensitive genotypes.

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Barbara M. Reed

Cold storage is important for managing in vitro germplasm collections. Strawberry shoot cultures can typically be held at 4 °C for 9 to 24 months before they require repropagation. Concentration of BA in the storage medium, pre-storage cold acclimatization (CA), and exposure to a photoperiod during storage were studied to determine conditions for improved strawberry culture storage. Fragaria shoot cultures stored at 4 °C were rated for plantlet condition on a 0-5 scale at 9, 12, and 19 months. Four species were CA and stored on medium with 0, 1, 2.5, or 5 μm BA either in darkness or under a 12-hour photoperiod. Mean ratings over all treatments and genotypes were best at 9 and 12 months (3.4) and declined at 19 months (2.2). BA in the storage medium significantly improved ratings for two species at 9 and 12 months, but ratings were not significantly different at 19 months. At 19 months of storage, shoot cultures stored with a photoperiod were rated significantly better (P ≤ 0.05) than those grown in darkness. Five Fragaria genotypes stored on medium without BA were used to study the effect of photoperiod and CA on ratings of stored plantlets. CA-shoot cultures stored for 9 or 12 months were rated significantly better than non-CA cultures. After 12 and 19 months storage, three of the five genotypes stored under a 12-hour photoperiod had significantly higher ratings than those stored in the dark (P ≤ 0.01), but by 19 months CA was nonsignificant. Overall, the addition of a photoperiod improved the condition of Fragaria shoot cultures stored at 4 °C. Chemical name used: N 6-benzyladenine (BA).

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Lisa J. Skog*, Theo Blom, Wayne Brown, Dennis Murr, and George Chu

Ozone treatment has many advantages for control of fungal diseases. There are no residue concerns, no registration is required, and it is non-specific, therefore potentially effective against a broad spectrum of pathogens. However, ozone is known to cause plant damage. There is little information available on either the ozone tolerance of floriculture crops or the levels required to kill plant pathogens under commercial conditions. Nine floriculture crops (begonia, petunia, Impatiens, Kalanchoe, pot roses, pot chrysanthemums, lilies, snapdragons and Alstroemeria) were subjected to increasing levels of ozone. Trials were conducted at 5 and 20 °C (90% to 95% RH) and ozone exposure was for 4 days for either 10 hours per day (simulating night treatment) or for 10 minutes every hour. Damage was assessed immediately after treatment and after an additional 3 days at room temperature in ozone-free air. Trials were terminated for the crop when an unacceptable level of damage was observed. Trials to determine the lethal dose for actively growing pathogens (Alternaria alternata, Alternaria zinniae and Botrytis cinerea) and fungal spores were conducted under identical conditions. Ozone tolerance varied with plant type and ranged between <0.2 and 3ppm. Generally, the crops surveyed were more susceptible to ozone damage at the low temperature. As a group, the bedding plants were the least tolerant. Fungal spores were killed at treatment levels between 0.8 and 2 ppm ozone. The actively growing fungal mycelium was still viable at 3 ppm ozone when the trial had to be terminated due to ozone-induced structural damage in the treatment chambers. Under the trial conditions, only the Kalanchoe would be able to tolerate the high levels of ozone required to kill the fungal spores.

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James R. Gorny and Adel A. Kader

Preclimacteric `Golden Delicious' apples (Malus domestica Borkh.) were stored at 0 °C in: air; air + 5% CO2; 2% O2 + 98% N2; or 2% O2 + 5% CO2 + 93% N2, and sampled monthly for 4 months to investigate the mechanism(s) by which reduced O2 and/or elevated CO2 atmospheres inhibit C2H4 biosynthesis. Ethylene biosynthesis rates and in vitro ACS activity were closely correlated in all treatments, while in vitro ACO activity significantly increased over time regardless of the treatment. Only a small amount of C2H4 biosynthesis inhibition by lowered O2 and/or elevated CO2 atmospheres could be accounted for by suppressed induction of ACO activity. Western blot analysis demonstrated that apples held for 2 months in lowered O2 and/or elevated CO2 atmospheres had significantly reduced abundance of ACO protein, compared to fruit held in air. Northern blot analysis of ACS and ACO transcript abundance revealed that reduced O2 and/or elevated CO2 atmospheres delay induction and reduce the abundance of both transcripts. Reduced O2 and/or elevated CO2 atmospheres reduce C2H4 biosynthesis by delaying and suppressing expression of ACS at the transcriptional level and by reducing the abundance of active ACO protein. Chemical names used: 1-aminocyclopropane-1-carboxylic acid (ACC), ACC synthase (ACS), ACC oxidase (ACO), ethylene (C2H4), S-adenosylmethionine (AdoMet).

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William J. Bramlage and Christopher B. Watkins

Seeking non-chemical alternatives to use of DPA for scald control on apples, we interrupted storage with a brief warming period. This often reduces chilling injuries of fruit. Warming `Granny Smith apples for 5 days at 20 C after 2 weeks at 0 C reduced scald as effectively as a 1000 ppm DPA treatment at that time. To better characterize this response, we tested other timings of the warming period, and also lower warming temperature. Warming at 10 C, or for shorter times at 20 C, or after longer periods at 0 C all were less effective. Maintaining a warm period before storage was not effective. During warming of `Cortland' and `Delicious' apples softening and loss of green color occurred, the extent of which increased with warming time and usually was greater if the fruit had initiated the ethylene climacteric before warming.

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Paul M. Chen and Diane M. Varga

`D'Anjou' pears (Pyrus communis, L.) growing in 3 locations with the elevation at 150 meters, 380 meters, and 610 meters respectively in Hood River valley, Oregon were harvested at the commercial maturity with the flesh firmness of 62.3 Newton (±2.2 N) and stored in air at -1°C. Regardless of different growing elevations, the incidence of superficial scald became noticeable after 2.5 months of storage and became substantial after 3 months. The rate of scald development was higher on the fruit from 150 meters elevation than those from higher elevations. Alpha-farnesene and conjugated trienes in the peel tissue accumulated at faster and higher rates in the fruit from 380 meters and 610 meters elevations than those from 150 meter elevation. The threshold level of conjugated trienes which causes superficial scald disorder was different from the fruit grown at different elevations.

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John M. Dole, Zenaida Viloria, Frankie L. Fanelli, and William Fonteno

, 1993 ), but cut big bend bluebonnet ( Lupinus havardii ) stems performed as well in floral foam as in water ( Davis et al., 1995 ). Cold storage is used to delay cut flower development and provide a long vase life ( Cevallos and Reid, 2001 ; Faragher

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Cristina Besada, Alejandra Salvador, Lucía Arnal, and Jose María Martínez-Jávega

treatments, temperature (°C) and duration (minutes), on persimmon fruit picked at Harvest II and Harvest III. After cold storage plus shelf life, every HWT that lasted for no more than 10 min resulted in very low firmness values, similar to the