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Christopher B. Watkins, Mustafa Erkan, Jacqueline F. Nock, Kevin A. Iungerman, Randolph M. Beaudry, and Renae E. Moran

`Honeycrisp' is a new apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] cultivar that has been planted extensively in North America, but the storage disorders soggy breakdown and soft scald have resulted in major fruit losses. The effects of harvest date and storage temperature on fruit quality and susceptibility of fruit to these disorders have been investigated in Michigan, New York, and Maine. Internal ethylene concentrations were variable over a wide range of harvest dates, and a rapid increase in autocatalytic ethylene production was not always apparent. The starch pattern index, soluble solids content, titratable acidity and firmness also appear to have limited use as harvest indices. Development of soggy breakdown and soft scald is associated with later harvest dates and storage of fruit at temperatures of 0 to 0.5 °C compared with higher storage temperatures. It is recommended that `Honeycrisp' be stored at 3 °C, although storage disorders still can occur at this temperature if fruit are harvested late. In addition, greasiness development may be worse at higher storage temperatures.

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James D. Hansen, Harold R. Moffitt, Dennis J. Albano, Millie L. Heidt, Stephen R. Drake, and Jacqueline L. Robertson

Confirmatory tests were performed on a two-component quarantine treatment against the codling moth (Cydia pomonella L.) (Lepidoptera: Tortricidae) for seven apple [Malus sylvestris (L.) var. domestica (Borkh.) Mansf.] cultivars ('Delicious,' `Golden Delicious,' `Braeburn,' `Fuji,' `Gala,' `Jonagold,' and `Granny Smith') intended for export to Japan and Korea. Treatment consists of a 55-day cold storage at 40 °F (2.2 °C) or below, followed by a 2-hour methyl bromide fumigation (0.056 oz/ft3 or 56 g·m-3) at 50 °F (10 °C). No eggs or larvae survived this treatment. Comparison tests were conducted on all cultivars to demonstrate no difference in insect responses between a previously accepted cultivar and proposed cultivars. Concentration-mortality responses were determined for each of the components and no statistical differences were found in the regression slopes of pest mortality with controlling variable (either cold exposure or fumigation) among all cultivars. Descriptive mathematical models, developed for the effects of cold storage on egg mortality and for methyl bromide fumigation on larvae mortality, were sigmoid curve equations.

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Monrudee Kittikorn, Katsuya Okawa, Hitoshi Ohara, Satoru Kondo, Nobuhiro Kotoda, Masato Wada, Mineyuki Yokoyama, Ohji Ifuku, Ariake Murata, and Naoharu Watanabe

and Methods Plant materials. Experiments were conducted in 2009 and 2010 on ‘Fuji’ apple trees grafted onto ‘Marubakaido’ rootstock ( Malus prunifolia Borkh. var. ringo Asami) growing in an open field of Chiba University located at lat. 36° N and

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Martin Harz, Moritz Knoche, and Martin J. Bukovac

Water conductance of the cuticle of mature fruit of apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf., `Golden Delicious' Reinders/`Malling 9' (M.9)], sweet cherry (Prunus avium L., `Sam'/`Alkavo'), grape (Vitis vinifera L.), pepper (Capsicum annuum L. var. annuum Fasciculatum Group, `Jive'), and tomato (Lycopersicon esculentum Mill.) was de ter mined using excised epidermal segments (consisting of epidermis, hypodermis, and some cell layers of parenchyma) and enzymatically isolated cuticular membranes (CM) from the same sample of fruit. Segments or CM were mounted in diffusion cells and transpiration was monitored gravimetrically. Conductance (m·s-1) was calculated by dividing the flux of water per unit segment or CM area (kg·m-2·s-1) by the difference in water vapor concentration (kg·m-3) across segments or CM. Transpiration through segments and through CM increased with time. Conductance of segments was consistently lower than that of newly isolated CM (3 days or less). Conductance decreased with increasing time after isolation for apple, grape, or sweet cherry CM, and for sweet cherry CM with increasing temperature during storage (5 to 33 °C for 4 days). There was no significant effect of duration of storage of CM on conductance in pepper or tomato fruit. Following storage of CM for more than 30 days, differences in conductance between isolated CM and excised segments decreased in apple, grape, and sweet cherry, but not in pepper or tomato. Use of metabolic inhibitors (1 mm NaN3 or 0.1 mm CCCP), or pretreatment of segments by freezing (-19 °C for 18 hours), or vacuum infiltration with water, had no effect on conductance of apple fruit segments. Our results suggest that living cells present on excised segments do not affect conductance and that epidermal segments provide a useful model system for quantifying conductance without the need for isolating the CM. Chemical names used: sodium azide (NaN3); carbonylcyanide m-chlorophenylhydrazone (CCCP).

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Gayle M. Volk, Adam D. Henk, Christopher M. Richards, Philip L. Forsline, and C. Thomas Chao

Geneva, NY, in the USDA-ARS NPGS apple collection. Most of the seedlots were assigned to the M. sieversii species, although some have been labeled as Malus sieversii var. kirghisorum (Al. Fed. & Fed.) Ponomar. The repository also has a number of

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P. Guy Lévesque, Jennifer R. DeEll, and Dennis P. Murr

Sequential decreases or increases in the levels of O2 in controlled atmosphere (CA) were investigated as techniques to improve fruit quality of `McIntosh' apples (Malus ×sylvestris [L.] Mill. var. domestica [Borkh.] Mansf.), a cultivar that tends to soften rapidly in storage. Precooled fruit that were harvested at optimum maturity for long-term storage were placed immediately in different programmed CA regimes. In the first year, CA programs consisted of 1) `standard' CA (SCA; 2.5–3.0% O2 + 2.5% CO2 for the first 30 d, 4.5% CO2 thereafter) at 3 °C for 180 d; 2) low CO2 SCA (2.5–3.0% O2 + 2.5% CO2) at 3 °C for 60 d, transferred to low O2 (LO; 1.5% O2 + 1.5% CO2) at 0 or 3 °C for 60 d, and then to ultralow O2 (ULO; 0.7% O2 + 1.0% CO2) at 0 or 3 °C for 60 d; and 3) ULO at 3 °C for 60 d, transferred to LO at 0 or 3 °C for 60 d, and then to SCA or low CO2 SCA at 0 or 3 °C for 60 d. In the second year, the regimes sequentially decreasing in O2 were compared with continuous ULO and SCA. After removal from storage, apples were held in ambient air at 20 °C for a 1-week ripening period. Fruit firmness was evaluated after 1 and 7 d at 20 °C, whereas the incidence of physiological disorders was assessed only after 7 d. Lowering the temperature while decreasing O2 was the best CA program with significant increased firmness retention during storage and after the 1-week ripening period. Reduced incidence of low O2 injury in decreasing O2 programs and absence of core browning at the lower temperature were also observed.

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Zhiguo Ju and Eric A. Curry

Effects of α-farnesene biosynthesis precursors on α-farnesene and ethylene production were studied using Lovastatin-treated or nontreated `Delicious' and `Granny Smith' apples [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.]. In nontreated fruit, α-farnesene was detected only in fruit peel (≈3 mm) and not in the more proximal cortical tissue. α-Farnesene was not detectable in preclimacteric fruit peel at harvest. Mevalonic acid lactone (MAL) or farnesyl pyrophosphate (FPP) induced α-farnesene production when fed to preclimacteric peel tissue, but hydroxymethylglutaric acid (HMG) did not. Fruit stored at 0 °C for 30 days (climacteric fruit) produced α-farnesene, and addition of HMG, MAL, or FPP further increased α-farnesene production. When treated at harvest with Lovastatin at 1.25 mmol·L-1 and stored at 0 °C for 30 days, fruit produced ethylene but did not produce α-farnesene. Whereas MAL and FPP induced α-farnesene production in peel sections from these fruit, HMG did not. Induction of α-farnesene by precursor feeding was concentration-dependent and had no effect on ethylene production. Cortical tissue sections from climacteric fruit did not produce α-farnesene unless HMG, MAL, or FPP were fed during incubation. Including Lovastatin at 0.63 mmol·L-1 in the feeding solution eliminated HMG induced α-farnesene production, but did not affect MAL or FPP-induced α-farnesene production. Neither precursor feeding nor Lovastatin treatment affected ethylene production in cortical tissues. Chemical name used: [1S-[1a (R°), 3α, 7β, 8β (2S°, 4S°), 8αβ]]-1,2,3,7,8,8α-hexahydro-3,7-dimethyl-8-[2-(tetrahydro-4-hydroxy-6-oxo-2H-pyran-2-yl)ethyl]-1-naphthalnyl 2-methylbutanoate (Lovastatin).

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J. Pablo Fernández-Trujillo, Jacqueline F. Nock, and Christopher B. Watkins

`Cortland' and `Law Rome' apples [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] were either nontreated or treated with the inhibitor of superficial scald development, DPA, and exposed to air or CO2 (40 or 45 kPa) in air at 2 °C for up to 12 days. Fruit exposed to air or 45 kPa CO2 were sampled during treatment, and peel and flesh samples taken for fermentation product and organic acid analyses. After treatment, fruit were air stored for up to 6 months at 0.5 °C for evaluation of disorder incidence. `Cortland' apples were most susceptible to external CO2 injury and `Law Rome' to internal CO2 injury. DPA treatment markedly reduced incidence of both external and internal injury. Fermentation products increased in peel and flesh of both cultivars with increasing exposure to CO2, but the extent of the increase was cultivar dependant. Acetaldehyde concentrations were about 10 times higher in peel and flesh of `Law Rome' than that of `Cortland' apples. Ethanol concentrations in the flesh were similar in both cultivars, but were about twice as high in `Cortland' than in `Law Rome' peels. Neither acetaldehyde nor ethanol concentrations were affected consistently by DPA treatment. Succinate concentrations, often regarded as the compound responsible for CO2 injury, increased with CO2 treatment, but were not affected by DPA application. Citramalate concentrations were reduced by CO2 treatment in `Law Rome' peel, but other acids were not consistently affected by CO2. Results indicate that acetaldehyde, ethanol or succinic acid accumulation are not directly responsible for CO2 injury in apples. Chemical name used: diphenylamine (DPA).

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Georgios Psarras and Ian A. Merwin

One-year-old potted `Mutsu' apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] trees on scion invigorating Malling-Merton 111 (MM.111) and scion dwarfing Malling 9 (M.9) rootstocks were grown outdoors in containers under three levels of water availability (irrigated at -20, -80, and -200 kPa) to investigate the effects of soil water availability on combined soil/root (rhizosphere) respiration rates, and developmental morphology of root systems. Rhizosphere respiration was measured with a portable infrared gas analyzer, and root biomass was estimated by electrical capacitance. These nondestructive measurements were compared with final root dry weights of harvested trees, to determine their reliability for estimating relative differences in root biomass. Water stress reduced final biomass similarly for both rootstocks, but the relative reduction in shoot growth was greater for MM.111. Root to shoot ratios were higher and average specific root respiration was lower for M.9 rootstock compared with MM.111. M.9 appeared to be more tolerant of water stress then MM.111, due to reduced canopy transpiration relative to root system mass. Water stress increased root to shoot ratios, specific root length, and the carbohydrate costs of root maintenance as indicated by specific respiration rates. Root dry weight (DW) was better correlated to rhizosphere respiration than to root electric capacitance. The observed r 2 values between root capacitance and root DW were as high as 0.73, but capacitance measurements were also influenced by soil water content and rootstock type. Electrical capacitance estimated total root biomass more accurately for M.9 than for MM.111.

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Zohar Shaham, Amnon Lers, and Susan Lurie

`Granny Smith' apples [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] were harvested in two seasons and stored at 0 °C air storage with no pretreatment (control), after heating for 4 d at 38 °C, or after treating for 16 hours at 20 °C with 1 μL·L-1 1-methylcyclopropene (1-MCP). The effects of the two treatments on superficial scald development were consistent over both seasons. Scald began to appear after 8 weeks in control fruit, after 16 weeks in heated fruit but not on 1-MCP treated fruit. α-Farnesene accumulation and oxidation were slower in the skin of heated than in control fruit, and almost entirely absent in 1-MCP treated fruit. The activities of five antioxidant enzymes, ascorbate peroxidase, catalase, glutathione reductase, peroxidase and superoxide dismutate, were measured at two-week intervals in the apple peel, quantitatively as total activity and qualitatively by isozyme analysis. Enzyme activities either increased or remained stable during 16 weeks of storage, except for superoxide dismutase activity, which decreased. Ascorbate oxidase activity was higher in heated than control apples and there was an additional peroxidase isozyme present in activity gels. The activities of antioxidant enzymes were lower in 1-MCP treated fruit except for catalase during the first month of storage. Lipid soluble antioxidant activity was higher in 1-MCP treated fruit than the fruit of the other treatments, and water soluble antioxidant activity was higher in both treatments than in control fruit during the time that scald was developing in control apples. Both free and total phenol contents in the peel fluctuated during storage but no consistent trend was detected. The differences in enzyme activity and antioxidant content of the peel of 1-MCP and heated apples may play a role in preventing or delaying the appearance of superficial scald.