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  • Author or Editor: William S. Conway x
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Abstract

‘Delicious’ apples (Malus domestica Borkh.) were pressure-infiltrated (68.95 kPa) above atmospheric at harvest with CaCl2, MgCl2, or SrCl2. After 5 months in storage at 0°C, the fruit were removed, wound-inoculated with a conidial suspension of Penicillium expansum, and kept for 7 days at 20°. Fruit then were rated for decay severity, ethylene production, respiration, firmness, and injury, and analyzed for the concentration of the appropriate cation. Calcium was the optimum cation for reducing decay, maintaining fruit firmness, and suppressing ethylene production. Cation treatments had little effect on respiration, and Mg was the only cation that caused distinctive injury to the fruit surface.

Open Access

Abstract

Fruit of ‘Golden Delicious’ apple (Malus domestica Borkh.) infiltrated after harvest with CaCl2 solutions of up to 12% (w/v) had lower ethylene production rates than untreated fruit during a 7-day period at 20°C immediately following treatment. However, after a 5-month storage period at 0° the effect of calcium on ethylene production diminished rapidly during a 7-day ripening period at 20°. Ethylene production for the 7-day period immediately following calcium treatment was correlated negatively to calcium concentration of the fruit. Calcium treatment had no significant effect on fruit respiration rate in this study. High calcium concentrations resulted in a decrease in the magnitude of ethylene production but had no effect on respiration. Titratable acidity and percentage of soluble solids were unaffected by calcium treatment even at high concentrations of CaCl2. Fruit firmness was correlated positively to calcium concentration of the fruit both before and after storage at 0°, and soluble polyuronide content of the fruit was correlated negatively to fruit calcium.

Open Access

Calcium has been linked to disease resistance in fruits and vegetables. The effects of calcium nutrition on six hydroponically grown tomato cultivars (`Switch', `Match', `Blitz', `Caruso', `Trust', and `Celebrity') were evaluated in the fall of 1996. Disease resistance and yield were measured for plants grown in either perlite or pine bark mulch. Plants were fertilized with a 5N–11P–26K water-soluble fertilizer solution containing micronutrients and either 60, 120, or 185 mg·L–1 calcium. Disease resistance was determined by measuring disease lesion diameters on mature green harvested fruit 3 to 5 days after inoculating with Botrytis cinerea Pers.: Fr. There was no significant difference in disease when evaluated by medium, cultivar, or calcium treatment. Foliar analysis by Inductively Coupled Argon Plasma Atomic Emission Spectrophotometer (ICAP) indicated that leaf calcium content ranged from 27,000 to 54,000 μg·g–1 dry weight (leaf above fifth flower cluster), but was not significantly different when analyzed by medium, cultivar, or calcium treatment. There was no significant difference in marketable yield due to medium or calcium treatment. Among cultivars, `Trust' had the highest marketable yield at 2.7 kg per plant, which was significantly different from `Celebrity' at 1.6 kg per plant. This experiment suggests that a cheaper medium (pine bark) and lower calcium levels can be utilized in fall tomato production.

Free access

An experiment was conducted to investigate the effect of Ca nutrition on yield and incidence of blossom-end rot (BER) in tomato. Three levels of Ca (low = 20 ppm, medium = 200 ppm, and high = 1,000 ppm; selected to represent very deficient, normal, and very high levels of calcium) were applied to three cultivars of tomatoes (`Mountain Supreme', `Celebrity', and `Sunrise'; selected to represent genetic differences in susceptibility to BER) grown in modified Hoagland solutions using a greenhouse hydroponic system. The experiment was constructed in a randomized complete-block design with three blocks, two replications, three cultivars, and three calcium treatments. The source of basic nutrients was a 5–11–26 soluble fertilizer containing micronutrients. The ratio of N–P–K was adjusted to 1.0–1.3–3.0 by adding NH4NO3 (34% N). Calcium was added as CaCl2. Nitrogen concentrations were maintained at 30 (first month), 60 (second month), and 90 ppm (during fruit growth), while the concentration of other nutrients followed proportionally. Cultivars differed significantly in yield and average fruit weight but not in incidence of BER or leaf Ca concentration. There was no cultiva × calcium treatment interaction. Leaf Ca content across cultivars was increased by 34% and 44%, respectively, by the medium and high Ca treatments. Average fruit weight and total yield per plant were not significantly different between the low and medium Ca treatments, however, both were reduced by the high Ca treatment. Incidence of BER was 95% higher in the low rather than in the medium Ca treatment. There was no significant difference in BER between the medium and high Ca treatments.

Free access

Three polyamine biosynthesis inhibitors, α-difluoromethylornithine (DFMO), α-difluoromethylarginine (DFMA), and α-methylornithine (MeOrn), alone and in combination with CaCl2, were tested for their ability to reduce in vitro growth and soft rot development in apple (Malus domestica Borkh.) fruit caused by Botrytis cinerea Pers.:Fr. and Penicillium expansum Link. All three inhibitors reduced the in vitro growth of the pathogens. Calcium had no effect on fungal growth in vitro. Pressure infiltration of millimolar concentrations of DFMO or DFMA or 25 g·L-1 CaCl2 solutions into apples reduced subsequent soft rot development by B. cinerea and P. expansum >40%. A combination treatment of Ca and DFMO or DFMA reduced decay >67%. Treatment of apples with MeOrn was less effective at inhibiting decay development. None of the inhibitors affected polyamine levels in apple cortical tissues. Some injury to the fruit surface was observed with Ca treatments. Fruit treated with Ca and any of the inhibitors were less firm than those treated with Ca alone. Specific polyamine biosynthesis inhibitors in combination with Ca may prove useful in reducing postharvest decay in apples.

Free access

Changes in tissue water relations, cell wall calcium (Ca) levels and physical properties of Ca-treated and untreated `Golden Delicious' apples (Malus×domestica Borkh.) were monitored for up to 8 months after harvest. Pressure infiltration of fruit with CaCl2 solutions at concentrations up to 0.34 mol·L-1 reduced both fruit softening and air space volume of fruit in a concentration-dependent manner. Turgor potential-related stress within the fruit persisted during storage and was higher in Ca-treated than in untreated fruit. Fruit that were pressure infiltrated with CaCl2 solutions between 0.14 and 0.20 mol·L-1 and then waxed to reduce water loss during storage showed no peel injury. Calcium efflux patterns from apple tissue disks indicated two distinct Ca compartments having efflux kinetics consistent with those for cell wall Donnan-phase bound and water free space soluble Ca. At Ca concentrations up to 0.20 mol·L-1, cell wall bound Ca approached saturation whereas soluble Ca showed a linear dependence. At higher external Ca concentrations, only soluble Ca in the tissue increased. During 8 months of cold storage, cell wall Ca-binding capacity increased up to 48%. The osmotic potential of apples harvested over three seasons ranged between-1.32 and -2.33 MPa. In tissue disks, turgor potential changes caused by adjusting the osmolality of the incubation solution with CaCl2 or sorbitol were accompanied by changes in the osmotic and water potentials of the tissue. In CaCl2 solutions up to 0.34 mol·L-1, turgor potential was ≥0.6 MPa in tissue incubated in 0.14 or 0.17 mol·L-1 solutions of CaCl2 and was more than 3 times higher than in tissues incubated in low (≤0.03 mol·L-1) or high (≥0.27 mol·L-1) concentrations of CaCl2. At osmotically equivalent concentrations, turgor potential was up to 40% higher in Ca-than in sorbitol-treated tissue. The results suggest that postharvest treatment with 0.14 to 0.20 mol·L-1 solutions of CaCl2 are best for maintaining fruit water relations and storage life of `Golden Delicious' apples while minimizing the risk of salt-related injuries to the fruit. While higher concentrations of CaCl2 may better maintain firmness, these treatments adversely affect fruit water relations and increase the risk of fruit injury.

Free access

Effects of postharvest pressure infiltration of distilled water, CaCl2 solutions at 0.14 or 0.27 mol·L-1 without and with subsequent fruit coating treatments of preclimacteric `Golden Delicious' [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf. `Golden Delicious'] apples on volatile levels, respiration, ethylene production, and internal atmospheres after storage at 0 °C for 1 to 6 months, and during subsequent shelf life at 20 °C were investigated. Over 30 volatiles were detected, most of the identified volatiles were esters; the rest were alcohols, aldehydes, ethers, a ketone, and a sesquiterpene. Pressure infiltration of water and increasing concentrations of CaCl2 resulted progressively in reduced total volatile levels, respiration, ethylene production, and internal O2 levels and increased CO2 levels in fruit following 2 to 4 months storage in air at 0 °C. Total volatile levels, respiration, ethylene production, and internal atmospheres of CaCl2-treated apples at 0.14 mol·L-1 gradually recovered to nontreated control levels following 2 weeks of shelf life at 20 °C and/or storage at 0 °C in air for more than 4 months. Following the calcium treatments with a shellac- or wax-based coating had similar but stronger and more persistent effects on volatile levels, respiration, ethylene production, and internal atmospheres than those found in fruit treated with CaCl2 alone. Calcium infiltration did not change the composition of volatile compounds found in fruit. Results suggest that pressure infiltration of `Golden Delicious' apples with CaCl2 solutions transiently inhibited volatile levels, respiration, and ethylene production, in part, by forming a more-or-less transient barrier to CO2 and O2 exchange between the fruit tissue and the surrounding atmosphere.

Free access

Pressure infiltration of `Golden Delicious' and `McIntosh' apples (Malus domestica Borkh.) with polyamides resulted in an immediate increase in firmness. `Golden Delicious' apples were 2.7 N (0.25 mM spermidine) to 6.7 N (1.0 mM spermine) firmer, while `McIntosh' apples were 2.2 N (0.25 mM spermidine) to 5.3 N (1.0 mM spermine) firmer than the water-treated control. During 28 weeks of storage at 0C, the differences between the polyamine-treated and water-treated apples were even larger. Similar results were observed with a 3% Ca treatment, but the Ca treatment reduced the rate of softening to a greater extent than did the polyamine treatments in `Golden Delicious'. Polyamides increased the endogenous levels of the polyamides infiltrated; however, the levels declined rapidly with time in storage. Both polyamine and Ca inhibited the development of chilling injury symptoms (brown core) in `McIntosh'. The influence of polyamines on ethylene production was negligible in both cultivars. The Ca treatment, however, inhibited ethylene evolution in `Golden Delicious'. Polyamides, thus, may affect apple softening through rigidification of cell walls rather than through interactions with ethylene metabolism.

Free access

Abstract

‘Golden Delicious’ apples (Malus domestica Borkh.) were pressure-infiltrated (68.9 kPa) at two harvest dates with 0%, 1%, 2%, or 4% (w/v) solutions of CaCl2 and stored at 0C for 2, 4, or 6 months followed by 1 week at 20C. Calcium concentrations, axial compression profiles, and Magness-Taylor firmness were measured. Calcium chloride infiltration increased all measures of tissue strength immediately and relative increases persisted during storage. A 1-week difference in harvest date markedly affected Ca uptake and textural responses; however, for both dates, 2% CaCl2 was effective in firming the apples. Apples from the second harvest, which were treated with 2% CaCl2 and stored for 6 months, had textural measurement values equal to or greater than those of comparable apples infiltrated only with water and measured before storage. Calcium chloride at 4% had a greater firming effect, but caused severe surface damage. Differential reponses to CaCl2 levels and storage durations by various textural measurements indicate that supplemental Ca not only increased firmness retention during storage, but also induced patterns of textural change different from those that occurred under the influence of the endogenous Ca alone.

Open Access

Abstract

The rate of postharvest softening of ‘McIntosh’ apples (Malus domestica Borkh.) was reduced by storage in a 1% O2 atmosphere at 1 or 3.5C. Apples stored in controlled atmosphere (CA) also maintained higher levels of the polyamines putrescine (PUT), spermidine (SPD), and spermine (SPN) in both skin and flesh tissues than those stored in air. The levels of putrescine and spermidine increased by 2- to 6-fold in CA-stored apples, while spermine decreased, but remained 2- to 5-fold higher than in air-stored fruit at both temperatures. Polyamines were also found to inhibit the in vitro activity of the cell wall-degrading enzyme polygalacturonase (PG). SPD and SPN were more effective than PUT, with SPN possessing the greatest inhibitory activity. These results are consistent with a hypothesis that increased polyamine levels are involved in the beneficial effects of CA storage and that polyamine activity could include the inhibition of cell wall degradation.

Open Access