Search Results
You are looking at 1 - 10 of 38 items for
- Author or Editor: William J. Bramlage x
Abstract
We expect that a plant of tropical or subtropical origin is chilling sensitive. A corollary might be that a plant not of tropical or subtropical origin is not chilling sensitive. Although there are exceptions to such a corollary, which I shall be describing, this evolutionary distinction is largely true because even those temperate crops that are chilling sensitive have developed survival mechanisms to circumvent this genetic liability.
Preharvest temperature (hrs. below 10°C) is a predictor of scald development on North American apples after long-term storage. In Mass., these variables are highly negatively correlated for both `Delicious' and `Cortland' apples. However, this predictor was not generally applicable for scald development on `Delicious' or `Granny Smith' apples in New Zealand. There, the relationship between temperature and scald varied greatly among districts for both cultivars, with scald resistance often occurring with far fewer hrs. below 10° than in Mass. Yet, in two cases when the temperature: scald relationship for `Granny Smith' was similar to that for `Cortland' and `Delicious' in Mass., temperature patterns during fruit ripening were similar to that in Mass. In all other cases, more moderate temperature changes occurred. These results suggest that the true base temperature for developing resistance to scald may be between 10° and 15°C, rather than 10°.
`Cortland' and `Delicious' apples were stored at 0C for up to 25 weeks, and at 20C in either open boxes or non-sealed poly bags for up to 8 weeks. At 20C, lesions occurred mostly around lenticels, but with some calyx bronzing and scald-like symptoms on shaded areas. At 0C, typical scald symptoms occurred. At both temperatures, high concentrations of alpha-farnesene and conjugated trienes occurred in conjunction with symptom appearance, and both these concentrations and discolorations decreased with later harvest of fruit. Scald development appeared to be chilling-enhanced, but not chilling-dependent.
Cool preharvest temperatures and increasing fruit maturity at harvest reduce poststorage superficial scald incidence. In the absence of cool preharvest temperatures, the role of fruit maturity in determining scald susceptibility becomes greater. Larger amounts of preharvest rainfall also contribute to reduction in scald incidence. Data from `Delicious' grown in a number of locations worldwide will be used to demonstrate this.
Cuticle provides a barrier for secretory of volatile lipophilic metabolites like α-farnesene in fruit. The accumulation and oxidation of α-farnesene or the propagation of its oxidation products can be affected by the thickness, the constituents, and the structure of this cuticle. To measure the development changes of cuticle components, `Delicious' trees were treated separately with 250 ppm aminoethoxyvinylglycine (AVG) on 12 Sept. and 200 ppm ethephon on 19 Sept. Fruit were harvested on 28 Sept. and stored at about 20C for 6 weeks. Total wax in both treatment and control fruit at harvest was around 2.8 mg/f.fr.wt. It increased rapidly after 2 weeks and reached 8.4 mg/g fr.wt. in control fruit after 6 weeks, which paralleled increasing internal ethylene and accumulation of α-farnesene. Ethylene synthesis, α-farnesene, and total wax accumulation were enhanced by ethephon treatment and completely suppressed by AVG treatment during the whole period of storage. The cutin contents in fruit from treated fruit and the control were similar at harvest, and they remained constant during storage.
Developmental changes in total cuticle and cuticular constituents were studied with `Delicious' fruit. Total wax (0.31 mg/cm2) and total cutin (0.54 mg/cm2, including carbohydrate polymers) were low in young fruit. They increased during fruit growth and reached 1.41 and 2.47 mg/cm2 of fruit peel at harvest, respectively. During fruit ripening at 20 °C, total cutin did not change, but total wax increased rapidly and reached 2.15 mg•cm-2 at 6 weeks. The increase of cuticular wax paralleled the increase of internal ethylene in fruit. Wax was separated by column chromatograph into four portions, hydrocarbons and wax esters, free alcohols, free fatty acids, and diols. More than half of the diols was ursolic acid. During fruit development, more hydrocarbons and diols accumulated in cuticle than free fatty acids and alcohols. During fruit ripening, all of the four portions increased, coincident with the climacteric rise in ethylene, but the increase rates of free fatty acids and alcohols were higher than those of other portions. Aminoethoxyvinylglycine (AVG, 220 mg•L-1) preharvest treatment inhibited internal ethylene synthesis to below 0.5 μL•L-1 during 6 weeks at 20 °C, and also inhibited wax accumulation. Ethephon (200 mg/L) preharvest treatment increased ethylene production and accelerated wax accumulation. α-farnesene accumulation coincided with increased internal ethylene and paralleled free fatty acid and alcohol accumulation.
Phenolics were extracted from fruit cuticles of `Delicious', `Golden Delicious', `Empire', and `Cortland' apples, using either cuticular wax scraped from fruit peel or enzyme-isolated cuticles. The concentrations of free phenolics in fruit cuticle ranged from 8 to 45 mg•g-1, and bound phenolics ranged from 50 to 110 mg•g-1 in these cultivars. Free cuticular phenolic concentrations in the four cultivars were in the order `Golden Delicious' > `Delicious' > `Empire' > `Cortland'. In a linoleate emulsion (oil-in-water) system, diphenylamine (DPA, lipophilic) displayed higher antioxidant activity than methanol-extracted cuticular phenolics (hydrophilic). In an α-farnesene-hexane (bulk oil) system, however, antioxidant activities of methanol-extracted cuticular phenolics were higher than that of DPA. Lipid-soluble antioxidants (LSAs) from cuticle displayed higher activity in the linoleate emulsion system than in α-farnesene-hexane system. Only about 10% to 15% of the total LSA activity in fruit peel was detected in isolated fruit cuticle. Among the four cultivars, LSA activity in epidermal and hypodermal cells was similar in `Golden Delicious', `Empire', and `Cortland' apples, while `Delicious' had lower activity.
Effects of fruit maturity, aminoethoxyvinylglycine (AVG) and 2-chloroethylphosphonic acid (ethephon) preharvest treatments, and storage conditions on cuticular phenolic concentration, α-farnesene oxidation, and scald susceptibility of `Delicious' apple were studied. Advanced maturity and ethephon reduced scald. AVG totally inhibited scald when the AVG-treated fruit were stored in low-ethylene room (<1 μL•L-1). In commercial room (ethylene >5 μL•L-1), however, AVG did not reduce scald. Advanced maturity and ethephon did not alter α-farnesene accumulation but significantly reduced conjugated triene (CT281) formation. AVG reduced α-farnesene and CT281 accumulation to very low levels in low-ethylene room but not in commercial room. Both advanced maturity and ethephon increased free phenolics in fruit cuticle, while AVG reduced them. Free cuticular phenolics increased during early storage in ethephon-treated and control fruit but not in AVG-treated fruit. Overall, free phenolics in fruit cuticle negatively correlated with formation of CT281 and scald susceptibility of apples. Neither fruit maturation nor AVG or ethephon treatment significantly affected lipid-soluble antioxidant concentration in fruit cuticle.
Seven types of chile peppers were tested for differences in susceptibility to postharvest chilling injury (CI). Cherry, cubanelle, Hungarian wax (HW), poblano, serrano, and both mature-green and full-color (red) jalapeño fruit were stored at 2.5, 7, and 15 °C for 0 to 30 days. External C2H4 production at 12 and 24 hours after removal from storage and internal C2H4 concentration at 24 hours were measured. There was no significant difference in C2H4 production after the first 12 hours, but serrano produced significantly less C2H4 than the other types during the second 12 hours. Among the cultivars there were differences in the amounts of internal C2H4 measured: HW had the highest levels measured, and serrano had undetectable levels. CI has been observed on bell and some chile pepper cultivars as small black pits, and the recommended nonchilling storage temperature is 7 °C for all peppers. In this study, scald (a surface browning) was observed on HW and cubanelle fruit in addition to pitting, which occurred on all the cultivars. Susceptibility to chilling varied among pepper types in this study. HW peppers were the most susceptible, manifesting scald after 4 days at 2.5 °C and scald and pits after 16 days at 7 °C. Serrano fruit were the most resistant to CI, only pitting after 23 days at 2.5 °C, and having no symptoms after storage at 7 °C for 30 days. Cherry and poblano peppers developed pits after 8 days at 2.5 °C. Both green and red jalapeños pitted after 12 days at 2.5 °C, and cubanelles had scald after 16 days at 2.5 °C. Poblano fruit had large, deep pits after 8 days at 7 °C, cherry peppers pitted after 12 days, and both green and red jalapeño fruit pitted after 16 days at 7 °C. Both pits and scald were observed on cubanelle fruit after 23 days at 7 °C. Recommendations for storage of peppers should be expanded to accommodate differences among cultivars.
Fruit from five regions worldwide were rated for scald development after four months in 0°C air plus one week at 20°C. Scald incidence was quantitatively related to preharvest temperature conditions and fruit maturity, as measured by starch index. Various low temperature cutoffs were used, and high temperatures over 30°C were also used in the equations. Where data were available light conditions and rainfall were included in the equations. Several models were developed and tested to determine if prediction equations could be of commercial value. The most successful equations explained over 50% of the variation in scald. While they could not predict exact percentages of fruit which would develop scald, equations could predict cases of very high and very low scald, thus identifying fruit requiring the greatest scald control measures and those needing minimal scald control action.