Search Results
You are looking at 21 - 30 of 57 items for
- Author or Editor: Donald J. Huber x
Three experiments were performed to characterize the physiological responses of an Eastern United States shipper muskmelon (Cucumis melo L. var. reticulatus ‘Athena’) harvested preripe (¼ slip) and during ripening (half-slip, full-slip) to 1 μL·L−1 1-methylcyclopropene (1-MCP), a potent ethylene antagonist effective at significantly extending the time required for climacteric fruit to complete ripening. In the first experiment, preripe fruit were treated with 1-MCP (18 hour, 20 °C) before storage at 15 °C. Softening of preripe ‘Athena’ was significantly suppressed in response to 1-MCP, with firmness of control and 1-MCP–treated fruit declining ≈50% and ≈36% through 12 and 18 days of storage at 15 °C, respectively. By 21 days of storage, firmness of 1-MCP–treated remained near 70 N, minimally within the upper range of whole-fruit firmness values considered acceptable for consumption (50–75 N). Fruit treated with 1-MCP exhibited significantly lower ethylene production, respiratory rates, and electrolyte leakage throughout storage. In a second experiment, muskmelon were treated with 1-MCP (18 hours, 20 °C) at progressively advanced stages of ripening (half- and full-slip stages). Softening was significantly suppressed in half-slip fruit, declining ≈64% and ≈23% in control and 1-MCP–treated fruit, respectively, during 16 days of storage at 15 °C. Advanced-ripening, full-slip fruit were similarly affected, softening ≈60% and ≈25% in control and 1-MCP–treated fruit, respectively, during 10 days at 15 °C. In a third experiment designed to simulate possible commercial handling protocols, full-slip muskmelon were treated with 1-MCP (24 hours, 10 °C) and held at 10 °C for 5 days before transfer to 20 °C. Mesocarp firmness of 1-MCP and control fruit within 2 days of transfer to 20 °C had decreased ≈40% and ≈54%, respectively, compared with values at the start of the experiment. After an additional 2 days at 20 °C, the mesocarp tissue of the respective treatments had softened 42% and 70%. Fruit treated with the ethylene antagonist showed significantly delayed incidence of surface decay and sunken regions compared with control fruit.
Interspecific hybrid squash (Cucurbita maxima × Cucurbita moschata) is a well-known cucurbit rootstock for controlling soilborne diseases and improving abiotic stress tolerance. However, reduced fruit quality has been reported on certain melon (Cucumis melo) cultivars when grafted with squash rootstocks. In this study, a field experiment was designed to explore fruit development and quality attributes of galia melon ‘Arava’ by grafting with hybrid squash rootstock ‘Strong Tosa’. Grafted plants with ‘Strong Tosa’ showed delayed anthesis of female flowers by ≈8–9 days, but harvest dates were unaffected compared with non- and self-grafted ‘Arava’ plants. Early and total yields were not significantly different between grafted and nongrafted plants. Grafted plants with ‘Strong Tosa’ rootstock exhibited accelerated fruit development and greater vegetative growth. During the harvest period, ≈27% of grafted plants with ‘Strong Tosa’ wilted, which was determined as nonpathogenic. Grafting with ‘Strong Tosa’ rootstock resulted in reduced fruit total soluble solids (TSS) and consumer rated sensory properties.
`Galia' (Cucumis melo var. reticulatus L. Naud. `Galia') melons exhibit relatively short postharvest longevity, limited in large part by the rapid softening of this high quality melon. The present study was performed to characterize the physiological responses of `Galia' fruit harvested at green (preripe) and yellow (advanced ripening) stages and treated with 1-methylcyclopropene (1-MCP) before storage at 20 °C. Treatment with 1.5 μL·L-1 1-MCP before storage delayed the climacteric peaks of respiration and ethylene production of green fruit by 11 and 6 d, respectively, and also significantly suppressed respiration and ethylene production maxima. Softening of both green and yellow fruit was significantly delayed by 1-MCP. During the first 5 d at 20 °C, the firmness of green control fruit declined 66% while 1-MCP-treated fruit declined 46%. By day 11, firmness of control and 1-MCP-treated green fruit had declined about 90% and 75%, respectively. The firmness of control yellow fruit stored at 20 °C declined 70% within 5 d while 1-MCP-treated fruit declined 30%. The 1-MCP-induced firmness retention was accompanied by significant suppression of electrolyte leakage of mesocarp tissue, providing evidence that membrane dysfunction might contribute to softening of `Galia' melons. The mesocarp of fruit harvested green and treated with 1-MCP eventually ripened to acceptable quality; however, under the treatment conditions (1.5 μL·L-1 1-MCP, 24 h) used in this study, irreversible suppression of surface color development was noted. The disparity in ripening recovery between mesocarp versus epidermal tissue was considerably less evident for fruit harvested and treated with 1-MCP at an advanced stage of development. The commercial use of 1-MCP with `Galia'-type melons should prove of immense benefit in long-term storage and/or export situations, and allow for retention of quality and handling tolerance for fruit harvested at more advanced stages of ripening.
Temperatures above 30 °C may delay or inhibit germination of most of commercial lettuce cultivars. Ethylene enhances lettuce seed germination at high temperatures. Enzyme-mediated degradation of endosperm cell walls appears to be a crucial factor for lettuce germination at high temperature. The galactomannan polysaccharides in lettuce endosperm cell wall are mobilized by endomannanase. The role of endo-mannanase during germination of lettuce seeds at high temperature (35 °C) and the possible role of etlene in enzyme regulation were investigated. Seeds of thermotolerant (`Everglades'-EVE) and thermosensitive (`Dark Green Boston'-DGB) lettuce genotypes were incubated at 20 and 35 °C in water, 10 mM of 1-aminocyclopropane-1-carboxylic acid (ACC), or 20 mM of silver thiosulphate (STS). Also, seeds were primed in an aerated solution of polyethylene glycol (PEG), or PEG+ACC, or PEG+STS. Untreated seeds germinated 100% at 20 °C. At 35 °C, EVE germinated 100%, whereas DGB germinated only 33%. Seed priming or adding ACC during imbibition increased germination of DGB to 100% at 35 °C. Adding STS during imbibition led to a decrease in germination at 35%C in EVE and completely inhibited germination of DGB. Priming with STS led to reduced germination at 35%C of both genotypes. EVE produced more ethylene than DGB during germination at high temperature. Providing ACC either during priming or during germination led to an increase in endo-mannanase activity, whereas STS inhibited mannanase activity. Higher endo-mannana activity was observed in EVE than DGB seeds. The results suggest that ethylene might overcome the inhibitory effect of high temperature in thermosensitive lettuce seeds via weakening of endosperm due to increased endo-mannanase activity.
Weakening of the endosperm tissue around the radicle tip before radicle protrusion and a potential role of endo-β-mannanase during germination of lettuce seeds (Lactuca sativa L.) at high temperature (35 °C) were investigated. Seeds from the thermotolerant genotypes `Everglades' and PI 251245 had greater endo-β-mannanase activity before radicle protrusion at 35 °C than the thermosensitive genotypes `Dark Green Boston', `Valmaine' and `Floricos 83'. Thermotolerant genotypes also generated more ethylene at high temperature. At 35 °C, germination of `Dark Green Boston' and `Everglades' seeds produced at days/nights of 20/10 °C was 10% and 32%, respectively, whereas germination of seeds produced at days/nights of 30/20 °C was 67% and 83%, respectively. Higher endo-β-mannanase activity was observed before radicle protrusion in `Dark Green Boston' seeds produced at 30/20 °C compared with those produced at 20/10 °C. A relationship between seed germination at high temperature, ethylene production, and an increase in endo-β-mannanase activity before radicle protrusion was confirmed.
Abstract
Postharvest changes in color and compositional characteristics were monitored in ‘Arkin’ and ‘Golden Star’ carambolas (Averrhoa carambola L.) before, immediately following, and 6 days after they were stored for 44 days at 5, 10, or 15C. General commercial practice has been to store this tropical fruit at 10C or higher to avoid possible chilling injury. Results from the present work demonstrated that fruit stored at 5C maintained better appearance, lost less weight, and exhibited less change in soluble sugar (glucose, fructose, and sucrose) or organic acid (oxalic and malic) concentrations than fruit stored at 10C. Rewarming experiments (6 days at 23C) indicated that these fruit had not lost the capacity to ripen normally and did not develop symptoms of chilling injury. Carambolas therefore can be stored most effectively at 5C.
1-Methylcyclopropene (1-MCP), an inhibitor of ethylene action, has been shown to extend the storage life of avocado fruit. Waxing is also known to extend the storage life of avocado by reducing water loss and modifying the fruit internal atmosphere. In this study, 1-MCP and waxing were used to investigate their effects on ripening characteristics in avocado fruit. Preclimacteric `Tower II' and `Booth 7' avocados were treated with 1-MCP (Ethylbloc®) for 12 h at 20 °C. Half of the fruit were waxed (Sta-Fresh 819F®, FMC Co.) after 1-MCP treatment. The fruit were subsequently stored at 13 °C or 20 °C at 85% RH. As evaluated by fruit firmness, ethylene evolution, and respiration rate, 1-MCP and waxing delayed the ripening of `Tower II' avocados stored at 20 °C. Fruit treated with both 1-MCP and wax had better retention of green peel color and fruit firmness, and the delayed climacteric pattern of ethylene evolution and respiration rates. Waxing reduced weight loss and retarded softening, but did not delay climacteric ethylene evolution and respiration rates. Whereas firmness of control fruit decreased from >100 N to 20 N in as few as 7 days at 20 °C, fruit treated with both 1-MCP and wax reached 20 N over 11 days at 20 °C. The firmness of `Booth 7' avocados treated with both 1-MCP and wax decreased from >170 N to 20 N over a 5-week period at 13 °C. Current studies are addressing the nature of the dramatic decrease in firmness of MCP-treated fruit.
Some nonmelting flesh (NMF) peaches develop a characteristic off-flavor during postharvest ripening. A study was conducted using NMF genotypes from the Univ. of Florida breeding program to investigate the off-flavor development in melting flesh (MF) and NMF peach genotypes and to determine the compositional changes associated with the development of off-flavor during postharvest ripening at 8 °C. The study revealed that there were certain chemical components that were consistently associated with the occurrence of off-flavor. Generally, there was a significant increase in total soluble phenolics, polyphenoloxidase (PPO) activity and ethanol content with the increase in the percentage of off-flavored fruit with time in storage at 8 °C in NMF genotypes examined. However, total sugars and total soluble solids decreased significantly during the storage period. These changes in chemical composition of NMF genotypes were not observed in MF genotypes, which did not show off-flavor development. Moreover, highly significant linear correlations were detected between off-flavor development and soluble phenolics, PPO activity, ethanol content, total soluble solids, and sugars in Fla. 92-21C and USDA 87P285, which had the highest percentage of off-flavored fruit. Specifically, soluble phenolics, chlorogenic acid, PPO activity, and ethanol were positively correlated, but soluble sugars and soluble solids were negatively correlated with the off-flavor development. Thus, it is suggested that the accumulation of soluble phenolic compounds and ethanol, and the reduction of soluble solids and sugars contribute to the of off-flavor in NMF genotypes.
Ethylene is integrally involved in the ripening of climacteric fruit. The ability to prevent ethylene action, or manipulate fruit sensitivity to ethylene, would provide a powerful means of extending postharvest storage life of these fruit, particularly for those that ripen rapidly and/or that are not tolerant of low-temperature storage. In this study, 1-methylcyclopropene (1-MCP), an inhibitor of ethylene action, was used to investigate ripening, respiration, and ethylene production in avocado fruit. `Monroe' avocados were treated with 1-MCP (Ethylbloc®) for 24 h at 20 °C. The fruit were subsequently stored at 13 or 20 °C. Some fruit were exposed to 100 ppm ethylene at 13 and 20 °C before or after MCP treatment. As evaluated by flesh firmness, respiration rate, and ethylene evolution, 1-MCP completely inhibited the ripening of avocado fruit stored at 13 and 20 °C and 85% relative humidity. Ethylene evolution and respiration rates were dramatically depressed, greater than 95% and 52%, respectively, by 1-MCP. Whereas firmness of control fruit decreased from over 100 N to 10 N in as few as 7 days, fruit treated with 1-MCP remained firm (>45 N) for periods of up to 3 weeks at 13 °C. Treatment of avocado fruit with 100 ppm ethylene at 20 °C for 12 h did not overcome the influence of MCP treatment. Similarly, treatment with ethylene before MCP exposure did not circumvent the effects of the cyclic olefin on ripening. Current studies are addressing the effects of MCP concentration and exposure time on avocado ripening.
Roma tomatoes (`Sunoma') were hand-harvested at the mature-green color stage and treated with 100 μL·L-1 ethylene for 60 h at 20 °C and 90% RH. Tomatoes at breaker ripeness stage (<10% red coloration) were sorted by weight (about 100 g) and half of the fruits were treated with 1-methylcyclopropene (1-MCP; 1 μL·L-1 for 24 h at 22 °C). After 1-MCP treatment, individual fruits were subjected to double impacts over the marked locular surface with force equivalent to a 40-cm height drop using a pendulum impactor. In non-1-MCP treated fruit, impacts increased the maximum respiration rate by 27% (to 39.1 mL·kg-1 per h) and ethylene production by 24% (to 5.5 μL·kg-1 per h). Treatment with 1-MCP decreased relative production of both CO2 (56%) and ethylene (54%) over non-1-MCP treated fruit, while the ripening period (as measured by softening and color development) was extended 2.5 times, to about 8 d. Fruits treated with 1-MCP had increased TTA (about 40%; 0.58% citric acid equivalent), decreased pH (5%), and no difference in soluble solids content (3.7 °Brix); double impacts did not affect these values. Double impacts accelerated the onset of polygalacturonase (PG) activity by about 100% (to 99.8 mol·kg-1 per min*10-5 D-galacturonic acid) at day 6 over non-impacted control fruit. 1-MCP treatment delayed the onset of increased PG activity by 10 d over non-1-MCP treated fruit. Although 1-MCP alleviated the impact-induced increase in PG activity, PG activity recovered to rates similar to those of non-1-MCP treated fruit during the final 4 d of ripening.