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Activity of phenylalanine ammonia-lyase (PAL) is critical in the induction of russet spotting (RS) in leaves of Iceberg lettuce (Lactuca sativa L.). RS is a major postharvest disorder of lettuce caused by exposure to ppm levels of ethylene at = 5C. Both PAL and RS are decreased when lettuce tissue previously exposed to ethylene is stored at = 15C or is transferred from = 5C to = 15C. To study the induction and inactivation of PAL, we exposed lettuce leaves to air ± 10 ppm ethylene at 5C for four days to initially induce high PAL levels. After four days, leaves were treated with water ± 2 mg/L cycloheximide, and transferred to air at 5 or 15 C. In leaves previously exposed to ethylene, PAL activity decreased rapidly to baseline levels within two days in non-cycloheximide treated leaves transferred to 15C. PAL activity remain elevated in the same treatment held at 5C. In leaves treated with cycloheximide and transferred to 15C, PAL did not begin to decrease until after four days. Cycloheximide treated leaves held at 5C showed increased PAL activity both two and four days after treatment.

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Some apple growers place specially designed bags with liners around fruit in the field to produce a unique surface color required by some premium markets. However, heat damage has been observed on `Fuji' apples that were bagged and reached high temperatures in the field. We tested different colored apple bags and their liners to determine the amount of light that is transmitted and whether bag color affected heating of the apples inside. Apple bags and liners were very effective at screening out sunlight; however, the absorbed light substantially warmed the bags and apples inside. No UV-A or B and less than 1% of photosynthetically active radiation (PAR) passed through the outer bag regardless of bag color and the inner liners transmitted ≈9% of the UV-A, 3% of the UV-B, and 30% of the PAR. When ambient air temperatures were only ≈25°C, dark green bags or red or green liners warmed the sun-facing apple surface to ≈43°C, while light green bags warmed to ≈36°C. Wrapping apple bags in aluminum foil to increase bag reflectivity greatly reduced heat buildup and maintained sun-facing fruit surface temperatures only slightly above air temperature (≈27°C). Possible design improvements for apple bags used in hot, sunny climates will be discussed.

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Adjacent but separate trials of `Oroblanco' and `Melogold', both triploid pummelo [Citrus grandis (L.) Osbeck] × grapefruit (Citrus paradisi Macf.) hybrids, were established on nine rootstocks in the Indian River citrus region of Florida in 1993. The trees on the citrandarin rootstock ×639 [Cleopatra mandarin (C. reticulata Blanco) × trifoliate orange (Poncirus trifoliata L.)] were significantly more productive than trees on any other rootstock tested for `Oroblanco' and all rootstocks except Swingle citrumelo (C. paradisi × P. trifoliata) and Cleopatra mandarin for `Melogold'. Cumulative production of `Oroblanco' on ×639, through year 9, was 50% higher than for Swingle or Volkamer lemon [C. limon (L.)], which were the next highest in yield. `Melogold' displayed extremely low yield, with 45% of trees producing fewer than 50 fruit total in the 9 years of this study. Carrizo citrange (C. sinensis Osbeck × P. trifoliata) produced the smallest trees with both scion varieties, reflecting poor adaptation of this rootstock to the calcareous soil at the trial site. As expected, acidity of `Oroblanco' and `Melogold' was much lower than would be observed for grapefruit when fall harvested, with similar total soluble solids (TSS), and much higher TSS: titratable acidity ratio. Some rootstock effects on internal quality were observed.

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The trunk diameter of ‘Valencia’ sweet orange trees tested with seven insect control strategies was measured annually for the first 5 years after planting. Yield data (marketable fruit per tree) were collected after the fourth and fifth years. The insect control treatments were Admire (imidacloprid) applied at 12, 6, 3, or 2-month intervals; Temik (aldicarb) applied annually; Meta-Systox-R (oxydemeton-methyl) applied annually; or no insect control. Trunk diameter was significantly increased by Temik treatment at 1 and 2 years after planting. Six annual applications of Admire (at 2-month intervals) significantly increased trunk diameter 2 years after planting. None of the other treatments affected trunk diameters compared with the control. There were no trunk diameter differences among treatments at 3, 4, or 5 years after planting. Both Temik applied annually and Admire applied every other month or every 3 months significantly increased yield.

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Warm field temperatures can often result in poor peel color of some citrus varieties, especially early in the harvest season. Under these conditions, Florida oranges, temples, tangelos, and K-Early citrus fruit are allowed to be treated with Citrus Red No.2 dye (CR2) to help produce a more acceptable peel color. Unfortunately, CR2, the commercial colorant used in Florida, has been listed as a group 2B carcinogen by the European Union (EU) and the International Agency for Research on Cancer (IARC). Although not likely dangerous at levels used on citrus, and on a part of the fruit that is not ingested, there is a negative health perception, and thus, a need for natural or food grade alternative colorants to replace CR2 for use on citrus. This research demonstrated that three out of five oil-soluble natural red/orange colorants resulted in peel colors somewhat similar to the industry standard CR2. These three (annatto extract, paprika extract, and paprika oleoresin) were selected for further in vivo studies. The stability of the natural colorants along with CR2 was evaluated by applying them on test papers and then on fresh ‘Hamlin’ oranges. All natural colorants were found to be easily oxidized and faded when applied on test papers. However, coating the colored surfaces with carnauba wax apparently inhibited oxidation and the subsequent discoloration of the surface. When applying the natural colorants to ‘Hamlin’ oranges before waxing, the treatments retained the improved color after storage in the dark at 5 °C, simulating cold storage. However, only annatto extract maintained a stable color when subsequently stored in a simulated market condition, at 23 °C exposed to 300 lx of standard fluorescent white light.

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In Florida, early season citrus fruits usually reach full maturity in terms of internal quality while their peel often does not turn to orange color after degreening due to insufficient buildup of carotenoids. For huanglongbing (HLB)-affected orange trees, the fruit may never turn orange during the entire harvest season, despite any cold weather. Improvement of early season citrus peel color is important to the citrus industry to better meet consumer expectations. Occasionally, packinghouses apply a dye, Citrus Red No. 2 (CR2), to improve the surface color of oranges, temples, and tangelos before applying a fruit wax to impart shine, retain moisture, and slow fruit senescence. In a previous report, we determined that paprika and annatto extracts are comparable to CR2 as natural colorant alternatives. In this research, the goal was to formulate a natural colorant [annatto, paprika, or paprika oleoresin (PO)]-containing carnauba wax coating. The coatings were first evaluated for color, shine, moisture retention, respiration rate, ethylene production, and internal gas content. Control fruit were coated with carnauba wax alone, or dyed with CR2 then coated with carnauba wax. The effects were assessed under different temperature and light exposure conditions to simulate commercial storage and marketing. The results showed that a one-step application of paprika-containing carnauba wax was comparable to the two-step (“CR2 then wax”) applications in improving fruit appearance and modification of internal gas composition.

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During the past 5 years, we have investigated the relationship between cherry skin color stages (light red, 50% bright red, 100% bright, and dark red) measured at harvest and harvest/shipping quality for `Brooks', `Tulare', and `King' cultivars. This relationship was studied with fruit grown in different geographic locations within the San Joaquin Valley (SJV). SSC increased, but titratable acidity levels did not change as cherries matured to the dark skin color. The perception of sweetness, sourness, and cherry flavor by a trained taste panel was related to the different cherry skin color stages. Dark red color developed on cherries picked at earlier color stages after simulated shipment. Pitting and stem browning were the main market life limitations. Pitting, stem browning, and decay were higher on cherries picked at the dark and 100% bright red colors than cherries picked at earlier stages.

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Previous research showed that mature green tomato fruit dipped 1 to 4 min in a 1% CaCl2 solutions before storage had significantly increased peel calcium content and reduced postharvest decay. The present experiments, conducted over 3-day periods (reps), evaluate treatment effectiveness under commercial packinghouse conditions. Three cartons of 5 × 6 sized mature green `FL 47' tomatoes were collected from the line (control). CaCl2 was then added to the packinghouse 15,142-L dump tank to a concentration of 1% before more fruit were run through the line and three additional cartons collected. The cycle was repeated after bringing the concentration in the dump tank up to 2% CaCl2. After storage for ≤24 days at 20 °C, postharvest decay was significantly reduced in fruit receiving the 2% CaCl2 treatment. Calcium content in the tomato peel tended to increase with each successively higher CaCl2 treatment, but differences were nonsignificant. Laboratory tests showed Rhizopus more affected by 3% CaCl2, while Alternaria was affected by 2% and 3% CaCl2 solutions. Results were recorded as colony diameter, but colony morphology and sporulation were also affected. Inoculation studies of tomatoes dipped in 1% CaCl2 after wounding with Rhizopus or Alternaria showed better decay control when compared to treating before wounding.

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Up to three hurricanes (Charley, Frances, and Jeanne) passed over the same citrus-producing areas of Florida in August and September 2004. In October 2005, hurricane Wilma also passed over South Florida. We began evaluating citrus tree recovery in four commercial groves (red and white grapefruit, and `Murcott' tangerine) following the 2004 hurricanes to determine how quickly commercial groves recover following such catastrophic events. We previously reported that, among other things, even branches formed after the last 2004 hurricane matured sufficiently to flower the following spring, but to a lesser extent than older shoots. Here, we report hurricane effects on tree yield, fruit quality, and shelf life. Fruit loss was dramatic following the 2004 hurricanes (>90%). Fruit loss was also substantial following hurricane Wilma, with `Murcott' yields reduced 18% and grapefruit yields reduced 58%-65%. However, in comparison to 2003 pre-hurricane yields, yields following hurricane Wilma declined only 9% for `Murcott,' and 26%-40% for grapefruit. These yield reductions are less than the fruit lost due to the present year's hurricane. Therefore, the citrus trees studied demonstrated tremendous resilience and, if not for another hurricane the following year, would have likely exceeded pre-hurricane yields only 1 year after the devastating 2004 hurricanes. Effects of the hurricanes on harvested fruit quality and shelf life will also be discussed.

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The development of ethylene preconditioning treatments for kiwifruit have made it possible to deliver ripe kiwifruit to consumers early in the season. We report on how maturity and length of storage time affect the ripening responses of kiwifruit [Actinidia deliciosa (A Chev) Liang et Ferguson cv Hayward] preconditioned with 100 ppm ethylene at 0°C for 24 hours and ripened for 10 days at 20°C. Kiwifruit freshly harvested at weekly intervals continued to soften faster in response to ethylene preconditioning compared to air controls for at least 5 weeks following commercial harvest. In contrast, kiwifruit commercially harvested and stored at 0°C for more than 2 weeks no longer responded to low-temperature ethylene preconditioning. However, kiwifruit stored more that 5 weeks were still responsive to exogenous ethylene and softened faster when exposed to continuous ethylene at either 0 or 20°C. Kiwifruit had relatively high respiration rates 1 days after transferring from 0 to 20°C, which quickly dropped to base levels within 1 day. Fruit stored >1 week at 0°C always had higher initial respiration than freshly harvested fruit on transfer to 20°C, and ethylene preconditioning increased initial respiration of freshly harvested fruit but had less of an effect on initial respiration of stored fruit. Plotting firmness against individual fruit's respiration and ethylene production revealed a distinct rise in respiration and ethylene production only after fruit softened to <6.5 N. Preconditioning fruit at 0°C did not significantly alter the timing of the climacteric respiration or ethylene peaks.

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