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In `Delicious' and `Granny Smith' apples, fruit did not produce α-farnesene until internal ethylene reached about 1 μL•L-1. The correlation between internal ethylene and α-farnesene production was highly significant (r 2 = 0.71 and 0.76, respectively) and fitted the exponential growth equation. Aminoethoxyvinylglycine (AVG) inhibited both internal ethylene and α-farnesene production, while ethephon stimulated them. When applied to discs from preclimacteric fruit peel, cycloheximide and actinomycin D inhibited ethylene and α-farnesene production. In discs from AVG-treated fruit, ethephon induced α-farnesene synthesis. Cycloheximide, actinomycin D, and silver ion counteracted the stimulation effect of ethephon. When added to discs from preclimacteric fruit peel or AVG-treated fruit peel, hydroxymethylglutarc acid, mevalonic acid lactone, and farnesyl pyrophosphate induced α-farnesene synthesis, which was not affected by cycloheximide or actinomycin D.

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At harvest, internal ethylene was >0.5 mL·L–1 and α-farnesene concentrations were below detectable levels in `Golden Supreme', `Delicious', and `Granny Smith' apples. After 30 days of storage at 20 °C, control fruit produced high levels of internal ethylene and α-farnesene. Lovastatin at 100 to 1000 mL·L–1 did not affect ethylene synthesis, but significantly inhibited α-farnesene production. In `Golden Delicious', ethephon treatment increased ethylene synthesis in lovastatin-treated fruit but did not stimulate α-farnesene production. In lovastatin-treated fruit peel of `Delicious' and `Granny Smith', mevalonate (MAL) and farnesyl pyrophosphate (FPP) induced α-farnesene production, but hydroxymethylglutaric acid (HMG) did not. The induction of α-farnesene synthesis by MAL and FPP was concentration-dependent. Precursor feeding did not affect ethylene production in fruit peel. When high level of α-farnesene was detected in fruit peel (5 mm thick), it was not found in outer (adjacent to peel) and inner cortex (mid of flesh) tissues. Adding HMG, MAL, and FPP induced α-farnesene biosynthesis in both cortex tissues. When lovastatin was added to the feeding solution, MAL and FPP induced α-farnesene production but HMG did not.

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Abstract

Deblossomed 8-year-old Malus domestica L. ‘Goldspur Golden Delicious’ trees on seedling rootstock exhibited less extension growth than trees that had carried a crop during either the current year or the previous year. Trees in the “on” year consistently had more extension growth than trees in the “off” year. Fruitful branches of ‘Golden Delicious’ and spur-type ‘Golden Delicious’ generally had more new growth than branches without fruit from the same tree.

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CPPU was applied to whole spur `Delicious' apple (Malus domestica Borkh.) trees in central Washington at 0,6.25,12.5,25, or 50 mg·liter-1 at full bloom (FB) or FB plus 2 weeks. At both application times, the flesh firmness of treated fruit linearly increased with increasing concentration. CPPU applied at 0,5,10,15, or 20 mg·liter-1 to spur `Delicious' trees in Massachusetts at king bloom resulted in a linear increase in flesh firmness at harvest and following 28 weeks in air storage at 0C. CPPU did not affect the incidence of senescent breakdown, decay, or cork spot. Fruit length: diameter (L/D) ratios generally increased at all doses. Fruit weight was not influenced at either location. All CPPU concentrations reduced return bloom on `Delicious' apples in Massachusetts in 1989. Of the 10, 20, or 40 mg·liter-1 treatments for `Empire' apples, only CPPU at 40 mg·liter-1 reduced return bloom. CPPU applied to `Empire' apples in Massachusetts did not effect fruit set, soluble solids concentration, L/D, or firmness; however, fruit weight increased linearly with concentration. CPPU applied at 100 mg·liter-1 retarded preharvest fruit drop of `Early McIntosh' in Massachusetts for ≈7 days but was not as effective as NAA at 20 mg·liter-1. In a larger semicommercial trial, `Delicious' fruit treated with CPPU at 5,10, or 15 mg·liter-1 at FB, petal fall (PF), or PF plus 1 week, respectively, were harvested and graded over a commercial packing line. Malformities caused by CPPU at the highest doses reduced packout, although all CPPU application rates reduced the percent fruit culled due to poor color. CPPU increased packed fruit size, since the size of fruit (64 mm in diameter) in the >150-fruit/box size decreased, while the size of fruit (72 mm in diameter) in the 100- and 130-fruit/box sizes increased. Treated fruit stored for 7 months at 1C were firmer than nontreated controls. Chemical names used: N-(2-chloro-4-pyridyl)- N' -phenylurea (CPPU); 1 naphthalene-acetic acid (NAA).

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Development of valid temperature-based models of physiological processes such as seed germination, bud development, vegetative growth, fruit development, or fruit maturation, requires a parameter to link temperature with plant metabolism. The Thermal Kinetic Window (TKW) concept uses the temperature characteristics of an enzyme kinetic parameter, the Michaelis constant (Km) as indicators of metabolic efficiency. Recently, Burke3 has shown that the temperature dependence of the rate and magnitude of the reappearance of photosystem II (PSII) variable fluorescence following illumination corresponded with the optimal temperature described by the TKW for several plant species. The present study investigated the use of the temperature sensitivity of PSII fluorescence in the identification of temperature optima of apple cultivars and rootstocks. 3Burke, J.J. 1990. Plant Physiol. 93:652-656.

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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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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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Effects of Lovastatin treatment on ethylene production, α-farnesene biosynthesis, and scald development were studied using `Delicious' and `Granny Smith' apples [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] and `d'Anjou' pears (Pyrus communis L.) stored in air at 0 °C. During 6 months storage, Lovastatin did not affect internal ethylene concentration but reduced α-farnesene production in a concentration dependent manner in both apples and pears. Lovastatin reduced scald at 0.63 mmol·L-1 and inhibited scald completely at 1.25 or 2.50 mmol·L-1 in `Delicious' and `Granny Smith' apples. In `d'Anjou' pears, Lovastatin at concentrations from 0.25 to 1.25 mmol·L-1 inhibited scald completely. After 8 months storage, inhibition of scald in both apples and pears by Lovastatin was concentration-dependent but none of the concentrations totally eliminated scald. Compared with 11.8 mmol·L-1 diphenylamine, Lovastatin treatment reduced scald to the same level at 1.25 mmol·L-1 in `d'Anjou' pear and 2.50 mmol·L-1 in `Delicious' and `Granny Smith' apples. Lovastatin did not affect apple or pear fruit color, firmness, soluble solids content, or titratable acidity during storage in either apple or pear compared with the controls. 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-naphthaienyl 2-methylbutanoate (Lovastatin).

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Abstract

Paclobutrazol (PP333) is a promising new bioregulant for controlling size of trees and significantly reducing the need for dormant and summer pruning. ‘Delicious’ trees were treated with a high rate of PP333, which resulted in some smaller, flattened fruit with shorter pedicels. Application of either gibberellin A4+7 plus 6-benzylamino purine (Promalin) or gibberellin A3 (GA3) before or at full bloom increased fruit size, pedicel length, and leaf size on PP333-treated trees.

Open Access

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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