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  • Author or Editor: Carolina Torres x
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Lenticel breakdown disorder (LB), most prevalent on ‘Gala’ (Malus × domestica) apples, especially in arid regions, has also been observed on other common cultivars. Depending on the preharvest environment, fruit maturity, and length of storage, LB usually appears as one or more round, darkened pits, centered on a lenticel, ranging in diameter from 1 to 8 mm. Symptoms are not visible at harvest nor are they usually apparent on unprocessed fruit after storage. However, following typical fruit processing and packing, symptoms are fully expressed after 12 to 48 h. Because the 3 to 4 weeks preceding ‘Gala’ harvest are usually the hottest and least humid, we theorized that desiccation stress was a main causative factor. Thus, several unique lipophilic formulations were developed that might reduce desiccation potential during this period of hot arid weather and rapid fruit enlargement. Emulsions of lipophilic formulations were applied to whole trees at various dosages and timings. In 2005, using a single handgun application 1 day before harvest, the best treatment reduced LB by about 20% in fruit stored 90 days at −1 °C. The following season, the best treatment from a single handgun application 7 days before harvest reduced LB by 35% after 90 days at −1 °C, whereas 3 weekly applications beginning 3 weeks before harvest reduced LB in similarly stored fruit by as much as 70%. In 2007, the best single treatment applied 1 week before harvest using a commercial airblast sprayer reduced LB by almost 50% after 90 days at −1 °C.

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Performance of seven apple (Malus ×domestica Borkh.) cultivars (‘Brookfield®Gala’, ‘Galaxy’, ‘Super Chief’, ‘Granny Smith’, ‘Fuji Raku Raku’, ‘Cripp's Pink’, and ‘Braeburn’) on M.M.106 and M.9 EMLA rootstocks during their first 6 years was evaluated on a multisite trial in Chile. Second-leaf trees were planted in experimental blocks inside commercial orchards located in five major apple-producing areas in Chile (Graneros, San Clemente, Chillan, Angol, and Temuco). Tree height and volume, trunk cross-sectional area (TCA), fruit yield and size distribution, crop load, and tree phenology were assessed annually. In general, tree growth rates by the end of the third year, when they reached the desired height, were similar in all block locations. M.9 EMLA rootstock reduced tree height by ≈20% in ‘Brookfield® Gala’, ‘Fuji’, ‘Galaxy’, and ‘Granny Smith’. This rootstock also had 50% smaller TCAs than M.M.106’s at Year 6 in most cultivars. The highest productions in ‘Brookfield®Gala’, ‘Galaxy’, ‘Granny Smith’, ‘Cripp's Pink’, and ‘Super Chief’, regardless of rootstock, were obtained in San Clemente and Chillan's blocks. Although M.M. 106 trees delivered higher yields per plant, M.9 EMLA yield efficiency (no. fruit/cm2 TCA) was significantly higher. In general, the higher the latitude (toward south), the later budbreak, full bloom, and harvest occurred.

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A distinct type of postharvest skin browning on apple (Malus domestica Borkh.) fruit called “stain” is a frequent disorder in ‘Fuji’ grown under high light and elevated temperatures. Symptoms typically develop only on sun-exposed sections of the fruit regardless of the presence of sunburn symptoms, and sometimes only in the margins of this area. The role of different antioxidant systems in tissue exposed to different levels of sunlight and having different degrees of sun injury were investigated during cold storage [1 °C, >90% (relative humidity) RH]. Ascorbic acid (AsA) and glutathione (GSH) concentrations, AsA–GSH recycling enzyme activities and gene expression, and flavonoids and carotenoid concentrations were determined every 30 days. “Stain” incidence increased with sun exposure and sunburn level. Both shaded and exposed fruit peel without sunburn symptoms had the highest AsA content. The AsA–GSH recycling enzyme activities and gene expression levels had no clear relationship with sun exposure during cold storage. Chlorophyll a (chl a) and chlorophyll b (chl b) levels diminished over time and were higher in tissue without any type of sun injury. In contrast, carotenoid levels increased as sun injury incidence increased and remained relatively stable during storage. Total phenolics and quercetin glycoside levels changed coincidently during storage. Results indicate that the AsA–GSH cycle does not have a clear role in “stain” development. Nevertheless, reduced ascorbate levels may reduce the capacity to prevent oxidative stress–provoked damage which may, in turn, result in oxidation of quercetin glycosides, which would then lead to skin browning.

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