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Zhiguo Ju and Eric A. Curry

Lovastatin is a specific hydroxymethylglutaryl coenzyme-A reductase inhibitor in animals and as such, is a potent cholesterol lowering pharmaceutical for human use. Because it has also been shown to inhibit α-farnesene in certain plants, we investigated its effects on ethylene and α-farnesene biosynthesis, volatile production, and fruit color during ripening in `Golden Supreme' apples [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.]. Immediately after harvest, fruit were dipped in Lovastatin solution for 2 min, allowed to dry, and stored in the dark at 20 °C for 30 days. Internal ethylene at harvest was low (< 0.1 mL·L-1) and α-farnesene was undetectable. Both internal ethylene and α-farnesene increased in nontreated fruit during 30 days storage. Prestorage Lovastatin treatment did not affect ethylene synthesis, but at 1.25 or 2.5 mmol·L-1 nearly eliminated α-farnesene production. At 0.25 mmol·L-1, Lovastatin delayed the increase in α-farnesene production about 12 days and reduced total α-farnesene production by the end of storage compared with controls. When applied to nontreated preclimacteric fruit, ethephon at 1.4 mmol·L-1 increased both internal ethylene concentration and α-farnesene production. In Lovastatin-treated preclimacteric fruit, however, ethephon increased internal ethylene concentration without promoting α-farnesene synthesis. In another trial, after 30 days storage at 0 °C, fruit were treated with 1.25 mmol·L-1 Lovastatin and stored at 20 °C with air circulation for 20 days. These fruit accumulated similar amounts of ethylene as nontreated controls, but α-farnesene production decreased rapidly and was not detectable after 5 days. Treating with ethephon at 1.4 mmol·L-1 increased α-farnesene production in control fruit but not in Lovastatin-treated fruit. Lovastatin treatment did not affect the change in fruit color. Chemical names used: [1S-[1α (R °), 3α, 7β, 8β (2S °, 4S °), 8ab]]-1,2,3,7,8,8α-hexahydro-3,7-dimethyl-8-[2-(tetrahydro-4-hydroxy-6-oxo-2H-pyran-2-yl)ethyl]-1-naphthaienyl 2-methylbutanoate (Lovastatin); 2-chloroethylphosphonic acid (ethephon).

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James M. Wargo, Ian A. Merwin, and Christopher B. Watkins

`Jonagold' apples [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] often fail to develop adequate red coloration at maturity and become soft and greasy in storage. During two growing seasons, we tested factorial combinations of three preharvest treatments affecting `Jonagold' quality at harvest and after storage: 1) three nitrogen (N) treatments [36 kg·ha-1 soil applied N, 6.9 kg·ha-1 of urea-N (1% w/v) in foliar sprays mid-May and June, or no N fertilizers]; 2) trunk girdling in early August each year; and 3) foliar applications of aminoethoxyvinylglycine (AVG, formulated as ReTain) 3 weeks before the first scheduled harvest. Fruit were sampled at four weekly intervals each year and evaluated for maturity and quality at harvest and after storage. Foliar urea and soil-applied N delayed red color development in 1998 but not 1999, increased fruit size in girdled and nonAVG treated trees in both years, and increased greasiness in 1999 only. AVG reduced fruit greasiness after storage both years. Nitrogen uptake was reduced in the dry Summer 1999, but N treatments still increased poststorage flesh breakdown. Mid-summer trunk girdling increased red coloration and intensity both years and improved market-grade packout. This effect was not caused by advanced maturity, although trunk girdling slightly increased skin greasiness. Girdling reduced fruit size only on trees of low N status. The AVG applications delayed maturity and red color development by 7 to 10 days in both years compared with untreated fruit. In 1998, the combination of AVG and N fertilization delayed red color development more than either treatment alone. Fruit softening and greasiness were reduced in AVG-treated fruit harvested at the same time as untreated fruit, but this effect was not observed when AVG treated fruit were harvested at comparable maturity 7 to 10 days later. Trunk girdling and withholding N fertilizer were the best treatments for enhancing red coloration, and foliar N concentrations of ≈2.0% (W/W) resulted in better packouts compared with higher leaf N levels. AVG was an effective tool for delaying fruit maturity and maintaining fruit quality awaiting harvest, but not for improving red coloration of `Jonagold' apples.

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Denise Neilsen, Peter Millard, Gerald H. Neilsen, and Eugene J. Hogue

Uptake, recycling, and partitioning of N in relation to N supply and dry matter partitioning was determined for 3- and 4-year-old `Elstar' apple trees [(Malus sylvestris (L) Mill. var. domestica (Borkh.) Mansf.] on Malling 9 rootstock in 1994 (year 3) and 1995 (year 4), respectively. Trees received N yearly as Ca(NO3)2 at 20 g/tree applied on a daily basis through a drip irrigation system. The fertilizer was labelled with 15N in year 3 to allow quantification of remobilization and uptake. The trees were not allowed to crop in years 1 and 2 and were not thinned in years 3 and 4, thereby establishing a range of crop loads. Dry matter and N contents were measured in fruit, midseason and senescent leaves and prunings collected in year 3, in midseason leaves, and in components of the whole trees, harvested in fall of year 4. Labelled N withdrawn from leaves in year 3 was less than that remobilized into leaves and fruit in year 4, indicating that senescent leaves were not the only source of remobilized N. Nitrogen uptake efficiency (total N uptake/N applied) in year 3 was low (22.3%). Of the N taken up, ≈50% was removed at the end of the growing season in fruit and leaves. In fall of year 4, the trees contained about 20 g N of which 50% was partitioned into leaves and fruit, indicating that the annual N uptake by young dwarf apple trees is low (≈10 g/tree). Data were pooled to compare dry matter and N partitioning into two major sinks: fruit and shoot leaves. Total fruit dry weight increased, and in year 4, fruit size decreased with fruit number, indicating that growth was carbon (C) limited at high crop loads. The number of shoot leaves initiated in both years was unaffected by fruit number, but leaf size decreased as fruit number increased in year 4. In year 3, the amount of both remobilized and root-supplied N in fruit increased with fruit number, but the N content of the shoot leaf canopy was unaffected. In general, N and C partitioning were coupled and leaf N concentrations were high (2.8% to 3.2%), suggesting that the low uptake efficiency of fertilizer N resulted because the availability of N in the root zone greatly exceeded demand.

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Kate M. Maguire, Nigel H. Banks, Alexander Lang, and Ian L. Gordon

Research quantified contributions to total variation in water vapor permeance from sources such as cultivar and harvest date in `Braeburn', `Pacific Rose', `Granny Smith', and `Cripps Pink' apples [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.]. In a study on `Braeburn' fruit from eight orchards in Central Otago, New Zealand, >50% of the total variation in permeance was associated with harvest date. This variation was the result of a large increase in water vapor permeance from 16.6 to 30.2 (se = 0.88, df = 192) nmol·s-1·m-2·Pa-1 over the 8 week experimental harvest period. Fruit to fruit differences accounted for 22% of total variation in permeance. Interaction between harvest date and orchard effects explained 7% of the total variation, indicating that fruit from the different orchards responded in differing ways to advancing harvest date. Tree effects accounted for only 1% of the total variation. Weight loss from respiration [at 20 °C and ≈60% relative humidity (RH)] comprised 3.04±0.11% of total weight loss, averaged across all harvest dates. In a second study of fruit of four apple cultivars, almost 30% of the total variation in water vapor permeance was associated with cultivar differences. Mean water vapor permeance for `Braeburn', `Pacific Rose', `Granny Smith', and `Cripps Pink' fruit was 44, 35, 17, and 20 (se = 4.3, df = 300) nmol·s-1·m-2·Pa-1 respectively. Over 20% of the total variation was associated with harvest date and arose from a large increase in water vapor permeance from 21 nmol·s-1·m-2·Pa-1 at first harvest to 46 nmol·s-1·m-2·Pa-1 (se = 5.3, df = 200) at final harvest, 10 weeks later, on average across all four cultivars. There was large fruit to fruit variation in water vapor permeance accounting for 25% of the total variation in permeance values. Tree effects only accounted for 4% of the total variation. Water vapor permeance in `Pacific Rose'` and `Braeburn' increased substantially with later harvest but values remained relatively constant for `Granny Smith' and `Cripps Pink'. A simple mathematical model was developed to predict weight loss from `Braeburn' fruit. Based on these findings, it appears worthwhile to increase the stringency of measures to control weight loss in `Braeburn' and `Pacific Rose'` apples, particularly those harvested late in the season.

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Mark A. Ritenour, Sunita Kochhar, Larry E. Schrader, Tsui-Ping Hsu, and Maurice S.B. Ku

Western immunoblot analyses showed that small heat shock proteins (smHSPs) are low or undetectable in the peel of `Fuji', `Jonagold', `Criterion', `Gala', and `Delicious' apples [(Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] growing shaded within the tree canopy (shade apples), but are high in apples growing exposed to direct sunlight (sun apples). `Fuji', `Jonagold', and `Gala' sun apples sampled biweekly between 1 July and 21 Oct. 1997 were highest in content of smHSPs on 31 July, 13 Aug., and 10 Sept., corresponding to some of the warmest periods of the sampling period. The smHSPs started to disappear first in `Gala', the earliest maturing cultivar, and last in `Fuji', the latest maturing cultivar indicating that maturity might play a role in regulating smHSP accumulation. In sun apple fruit left on trees for 60 to 120 days beyond commercial maturity and exposed to field temperatures as low as -4 °C, a 71.7 ku (u = unified atomic mass unit) polypeptide was detected with a polyclonal antiwheat (Triticum aestivum L.) HSP70 in the peel and cortex of all five cultivars. While no smHSPs were detected in these apples, three smHSPs, as detected by antibodies against pea (Pisum sativum L.) cytosolic HSP18.1, could be induced in the same fruit 24 hours after heating to 45 °C for 4 hours. In `Fuji' shade apples heated at 40 °C, smHSP accumulation was detected after the second hour of a 4-hour heat treatment and continued to increase over the next 48 hours at 22 °C. Levels of HSP70 did not change in `Fuji' shade apples heated at 45 °C for 2, 4, or 6 hours, but smHSPs became detectable immediately after each of these heat treatments and further increased over the next 24 hours at 22 °C. Accumulation of smHSPs was maximal in the 4-hour heat treatment. After a 4-hour heat treatment at 45 °C, smHSPs increased during the next 48 hours at 22 °C and then declined by 72 hours. Using two-dimensional electrophoretic analysis, as many as 17 proteins ranging from 15 to 29 ku were found to accumulate in the peel 48 hours after a 4-hour heat treatment. Thus, apples can respond rapidly to high temperature stress, even at advanced stages of maturity, by synthesizing smHSPs, which likely play an important role in protecting cellular biochemical processes during these periods of stress.

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Luiz C. Argenta, Xuetong Fan, and James P. Mattheis

The efficacy of the ethylene action inhibitor 1-methylcyclopropene (1-MCP) applied in water to slow ripening of ‘Golden Delicious’ [Malus sylvestris var. domestica (Borkh.) Mansf.] apples was evaluated in comparison with 1-MCP applied in air. The material was applied by dipping fruit in 1-MCP water solutions (0.03, 0.3, or 3 mmol·m−3) for 4 min or by exposing fruit to 1-MCP gas (0.42, 4.2, or 42 μmol·m−3) in air for 12 h. Fruit were held in air at 20 °C for 25 days after treatment or stored at 0.5 °C in air for up to 6 months followed by 7 days in air at 20 °C. Application of 1-MCP in water or air delayed the increase in respiration and ethylene production associated with fruit ripening and reduced the amount of fruit softening, loss of acidity, and change in peel color. Treatments applied in water required a 700-fold higher amount of active ingredient compared with treatments applied in air to induce similar physiological responses. Fruit responses to 1-MCP varied with treatment concentration, and the maximum effects were obtained at concentrations of 4.2 or 42 μmol·m−3 in air and 3 mmol·m−3 in water. Peel color change was impacted less than retention of firmness and titratable acidity for 1-MCP treatments applied at concentrations of 4.2 or 42 μmol·m−3 in air and 0.3 or 3 mmol·m−3 in water. Treatment with 1-MCP in air or water was less effective for slowing peel degreening when treated fruit were stored at 0.5 °C compared with storage at 20 °C. Fruit treated with 1-MCP and stored in air at 0.5 °C developed a peel disorder typified by a gray·brown discoloration that is unlike other disorders previously reported for this cultivar. Symptoms were present when fruit were removed from cold storage and no change in symptom appearance was observed during a 7-d holding period at 20 °C.

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Nazir A. Mir, Erin Curell, Najma Khan, Melissa Whitaker, and Randolph M. Beaudry

Fruit of `Redchief Delicious' apple [Malus sylvestris (L) Mill. var. domestica (Borkh.) Mansf.] were harvested 1 week before the climacteric (harvest 1), at the onset of the climacteric (harvest 2), and 1 week after the onset of the climacteric (harvest 3). Fruit were stored at 0, 5, 10, 15, or 20 °C and were treated with 0.7 μL·L-1 1-MCP on a once-per-week, once-per-2-week, once-per-month, and once-per-year basis or were left nontreated. The initial 1-MCP treatment was at 20 °C and subsequent applications were at storage temperatures. The compound slowed softening at all temperatures relative to nontreated fruit, however as temperature decreased, the benefits of 1-MCP application became less pronounced. Effectiveness of 1-MCP declined slightly as harvest maturity increased. Efficacy of 1-MCP treatment increased with greater frequency of application at 5, 10, 15, and 20 °C, but not at 0 °C. Fruit stored without refrigeration (20 °C) for more than 100 days did not soften significantly when treated once per week with 1-MCP. However, decay was a significant problem for treated and nontreated fruit stored at temperatures >5 °C; 1-MCP application reduced, but did not prevent decay. Rate of decline in titratable acidity increased with storage temperature and 1-MCP had no significant effect on retarding the decline in acid content. Minimal (Fo) and maximal (Fm) chlorophyll fluorescence was altered markedly by 1-MCP application, but the ratio of (Fm-Fo)/Fm was only slightly affected. The most effective 1-MCP treatment frequency was once per week and, at all elevated temperatures (5, 10, 15, and 20 °C), slowed loss of firmness to a greater extent than refrigeration (0 °C) alone. Application of 1-MCP resulted in greater retention of firmness than controlled atmosphere (CA) with O2 and CO2 at 1.5 kPa and 3 kPa, respectively. Data suggest that 1-MCP application, has the potential to reduce reliance on refrigeration and CA storage for maintaining firmness of `Redchief Delicious' apple, especially for relatively short storage durations (<50 days) when fruit are harvested within a week of the ethylene climacteric. Chemical name used: 1-methylcyclopropene (1-MCP).

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Lihua Fan, Jun Song, Charles F. Forney, and Michael A. Jordan

Ethanol concentration and chlorophyll fluorescence (CF) were measured as signs of heat stress in apple fruit [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.]. `McIntosh', `Cortland', `Jonagold', and `Northern Spy' apples were placed in trays and exposed to 46 °C for 0, 4, 8, or 12 hours. Following treatments, fruit were stored in air at 0 °C and evaluated after 0, 1, 2, or 3 months. Ethanol and ethylene production, CF, peel and flesh browning, firmness, skin color, soluble solids, and titratable acidity were measured. Increases in ethanol were apparent immediately following 12-hour heat treatments as well as after 3 months. After 3 months, ethanol concentrations were 16-, 52-, 6-, and 60-fold higher in `McIntosh', `Cortland', `Jonagold', and `Northern Spy' apples than in controls, respectively. The concentrations of ethanol accumulated reflected the degree of heat-induced fruit injury. Heat treatments reduced ethylene production relative to control values. After 3 months of storage ethylene production of fruit exposed to 46 °C for 12 h was <0.48 μmol·kg-1·h-1 compared to >4.3 μmol·kg-1·h-1 for controls. Heat treatments also reduced CF which was expressed as Fv/Fm, where Fv is the difference between the maximal and the minimal fluorescence (Fm - Fo), and Fm is the maximal fluorescence. After 3 months storage at 0 °C, Fv/Fm was ≈0.2 in fruit held at 46 °C for 12 hours compared with 0.5-0.6 for control fruit. Exposure to 46 °C for 12 hours caused severe peel and flesh browning in all cultivars. Severity of peel and flesh browning increased with increasing duration of heat treatment and subsequent storage at 0 °C. `Northern Spy' apple fruit were most susceptible to heat stress based on the degree of flesh browning. Heat treatments of 8 and 12 hours reduced firmness of `McIntosh', `Cortland', and `Northern Spy', but not `Jonagold' apples. Hue angle of the green side of fruit was also reduced in `Cortland', Jonagold' and `Northern Spy' apples receiving the 8- and 12-hour treatments. Heat treatments caused a decrease in fruit tiratable acidity, but had no effect on soluble solids content. The increase in ethanol production and decrease in CF correlated with heat-induced injury, and were apparent before browning was visually apparent. Ethanol and CF have the potential to be used to nondestructively predict the severity of injury that develops during storage.

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Maria M. Jenderek, Phil Forsline, Joseph Postman, Ed Stover, and David Ellis

? This study investigated post-cryoviability of DB for three commercial cultivars of Malus domestica grown in three distinct geographic locations, Geneva, NY, Davis, CA, and Corvallis, OR. Material and Methods The commercial M. domestica cultivars

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Gennaro Fazio, Yizhen Wan, Dariusz Kviklys, Leticia Romero, Richard Adams, David Strickland, and Terence Robinson

Malus × domestica cluster when molecular markers were used to ascertain their relationships. Some (including M.8 and M.9) formed a tight cluster, suggesting close familial relationships ( Fazio et al., 2011 ; Oraguzie et al., 2005 ). Some have