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D.R. Rudell, J.P. Mattheis, X. Fan, and J.K. Fellman

Effects of artificial ultraviolet-visible light and methyl jasmonate (MJ) treatment on `Fuji' apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] fruit peel anthocyanin, phenolic, carotenoid, and chlorophyll production were examined using tristimulus color analysis and reverse-phase high performance liquid chromatography. Anthocyanin synthesis was enhanced by light and MJ treatment. Chlorogenic acid and most cyanidin, quercetin, and phloretin glycosides increased with MJ treatment concentration. Light alone also promoted increased production of most of these compounds. Production of catechin, (-)epicatechin, quercetin, and quercetrin was not enhanced by either light or MJ treatment. Light and MJ enhanced ß-carotene and chlorophyll b, synthesis but not xanthophyll or chlorophyll a synthesis. The chlorophyll a/b ratio decreased with MJ dosage. Results suggest MJ may provide a viable means of enhancing apple fruit coloration and other photoprotective mechanisms. Chemical name used: methyl 3-oxo-2-(2-pentenyl)cyclopentane-1-acetate (methyl jasmonate).

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James M. Wargo and Chris B. Watkins

`Honeycrisp' apples (Malus × domestica) were harvested over 3-week periods in 2001 and 2002. Maturity and quality indices were determined at harvest. Fruit quality was evaluated after air storage [0.0 to 2.2 °C (32 to 36 °F), 95% relative humidity] for 10-13 weeks and 15-18 weeks for the 2001 and 2002 harvests, respectively. Internal ethylene concentrations (IEC), starch indices (1-8 scale), firmness and soluble solids content (SSC) did not show consistent patterns of change over time. Starch hydrolysis was advanced on all harvest dates, but it is suggested that a starch index of 7 is a useful guide for timing harvest of fruit in western New York. After storage, firmness closely followed that observed immediately after harvest, and softening during storage was slow. No change in SSC was observed during storage in either year. Incidence of bitter pit and soft scald was generally low and was not affected consistently by harvest date. The incidence of stem punctures averaged 18.5% over both years, but was not affected by harvest date. Development of stem end cracking in both years, and rot development in one year, increased with later harvest dates. A panel of storage operators, packers, growers, and fruit extension specialists evaluated the samples for appearance and eating quality after storage, and results suggested that a 2-week harvest window is optimal for `Honeycrisp' apples that are spot picked to select the most mature fruit at each harvest.

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Iwan F. Labuschagné, J.H. Louw, Karin Schmidt, and Annalene Sadie

Genetic variation in chilling requirement was investigated over three growth periods using clonal progenies of six apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] families derived from crosses of high and low chill requiring cultivars. Two quantitative measurements related to chilling requirement, viz., the time of initial budbreak (vegetative and reproductive) and the number of breaking buds over a specified time interval, were used as evaluation criteria. Genetic and environmental variances of the traits are presented as intra-class correlation coefficients for clones within and between families. For budbreak time, reproductive and vegetative, broad-sense heritability averaged around 75% and 69% respectively, indicating a high degree of genetic determination in this material. For budbreak number, moderate to low genetic determination was found with broad-sense heritabilities around 30%. Estimates of genetic components of variance between families were generally very low in comparison to the variance within families and predict potentially favorable responses to truncation selection on the traits within these progeny groups. Analysis of the data showed that distribution of budbreak time is typical of quantitative traits with means distributed closely around midparent values. Skewed distributions towards low budbreak number were obtained in varying degrees in all families.

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Satoru Kondo, Kentaro Hiraoka, Shozo Kobayashi, Chikako Honda, and Norihiko Terahara

Cyanidin 3-galactoside was the primary anthocyanin in red `Tsugaru' apples [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.]. The concentration of cyanidin 3-galactoside in the skin decreased from 20 to 62 days after full bloom (DAFB), then increased rapidly after 104 DAFB. Small amounts of cyanidin 3-arabinoside and cyanidin 3-glucoside were detected at 122 and 133 DAFB (harvest). The expression of five anthocyanin biosynthetic genes of chalcone synthase (MdCHS), flavanone 3-hydroxylase (MdF3H), dihydroflavonol 4-reductase (pDFR), anthocyanidin synthase (MdANS), and UDP glucose-flavonoid 3-O-glucosyltransferase (pUFGluT) was examined in the skin of red and nonred apples. In general, the expression of anthocyanin biosynthetic genes in red apples was strong in juvenile and ripening stages. The expression of MdCHS, MdF3H, pDFR, and MdANS was observed before ripening stage when anthocyanin was not detected. In contrast, the expression of pUFGluT was detected in the development stage only when anthocyanin was detected. However, the expression of all five genes was observed at 20 DAFB in fruit bagged after fertilization, and anthocyanin was not detected. The expression of MdCHS, MdF3H, pDFR, and MdANS, excluding pUFGluT, was detected at 98 DAFB in fruit bagged after 30 DAFB, and anthocyanin was not detected. These results suggest that pUFGluT may be closely related to the anthocyanin expression in apple skin at the ripening stage.

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Pierre-Éric Lauri and Jean-Marie Lespinasse

Growing shoots of two apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] genotypes differing in shoot architecture, the preselection X.3318 and the cultivar `Chantecler', were bent on three dates during the summer and one in the winter to evaluate the interactive effects of shoot architecture and bending date on lateral shoot development and growth over 3 years. Bending X.3318, with a high proportion of vegetative lateral shoots on 1-year-old wood, on different dates did not change the percentage of lateral budbreak (62% to 65%). However, bending in June or July increased lateral growth on 1- and 2-year-old wood in a mesotonic position, whereas bending in winter reduced lateral growth and redistributed the shoots more basitonically. Both number and weight of fruits were reduced by bending. In `Chantecler', which forms many flower buds on 1-year-old wood, bending during flower bud formation (June-July) increased the percentage of lateral budbreak (60% vs. 45% for the control) and the number of flower buds. After 3 years of development, early summer treatments reduced the abortion of laterals as compared to the control. As a consequence, bending increased the number, as well as the weight of fruit. These results show that the effects of bending on the development and growth patterns of lateral shoots vary with genotype.

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D. Michael Glenn and Stephen S. Miller

This study examines the effect of multiple spray applications of Apogee on shoot growth and whole-canopy photosynthesis (WCPn) rate in young, bearing apple trees. Apogee increased fruit numbers and reduced shoot growth and inconsistently reduced leaf area but the reduction in photosynthetic area did not result in reduced WCPn or a detrimental effect on the fruit number:fruit size relationship. Since WCPn was not affected when leaf area was reduced by Apogee treatment, it suggests a greater photosynthetic efficiency of leaves on Apogee treated trees due to reduced shading. The use of Apogee for canopy management may produce a side-effect of increasing fruit set, which may be managed through a crop thinning program.

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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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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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Satoru Kondo, Akihiro Tomiyama, and Hideharu Seto

Trans-jasmonic acid (JA), cis-JA, and trans-methyl jasmonate (MeJA) were quantified in pulp and seeds of `Tsugaru' apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] and `Satohnishiki' sweet cherry (Prunus avium L.). Trans-JA and cis-JA showed similar changes during development in both types of fruit. JA concentration was high in the early growth stages of apple pulp development, decreased with days after full bloom (DAFB), and then increased again during maturation. There was an initial decrease in concentration of MeJA in apple pulp, followed by a general increase towards harvest. Concentrations of JA and MeJA in the pulp of sweet cherry were high during early growth stages, then decreased towards harvest. PDJ treatment at 104 DAFB (preclimacteric stage) increased endogenous abscisic acid concentration and anthocyanin concentration at 122 and 131 DAFB (maturation stages) in apple. JA concentration in apple seeds was also high in the early growth stages, then decreased, and finally peaked at harvest. MeJA concentration in apple seeds increased towards harvest. In the seeds of sweet cherry, JA and MeJA concentrations generally increased until harvest. In both types of fruit, concentrations of JA and MeJA in the seeds were higher than those of pulp. On a dry weight basis, changes in concentration in the seeds preceded those in the pulp. These results demonstrate that relatively high amounts of JA and MeJA are associated with young developing fruit. These substances may have a role in regulation of fruit growth at early growth stages, though this has not been demonstrated. Chemical name used: n-propyl dihydrojasmonate (PDJ).

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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.