Seeking non-chemical alternatives to use of DPA for scald control on apples, we interrupted storage with a brief warming period. This often reduces chilling injuries of fruit. Warming `Granny Smith apples for 5 days at 20 C after 2 weeks at 0 C reduced scald as effectively as a 1000 ppm DPA treatment at that time. To better characterize this response, we tested other timings of the warming period, and also lower warming temperature. Warming at 10 C, or for shorter times at 20 C, or after longer periods at 0 C all were less effective. Maintaining a warm period before storage was not effective. During warming of `Cortland' and `Delicious' apples softening and loss of green color occurred, the extent of which increased with warming time and usually was greater if the fruit had initiated the ethylene climacteric before warming.
Preclimacteric `Golden Delicious' apples (Malus domestica Borkh.) were stored at 0 °C in: air; air + 5% CO2; 2% O2 + 98% N2; or 2% O2 + 5% CO2 + 93% N2, and sampled monthly for 4 months to investigate the mechanism(s) by which reduced O2 and/or elevated CO2 atmospheres inhibit C2H4 biosynthesis. Ethylene biosynthesis rates and in vitro ACS activity were closely correlated in all treatments, while in vitro ACO activity significantly increased over time regardless of the treatment. Only a small amount of C2H4 biosynthesis inhibition by lowered O2 and/or elevated CO2 atmospheres could be accounted for by suppressed induction of ACO activity. Western blot analysis demonstrated that apples held for 2 months in lowered O2 and/or elevated CO2 atmospheres had significantly reduced abundance of ACO protein, compared to fruit held in air. Northern blot analysis of ACS and ACO transcript abundance revealed that reduced O2 and/or elevated CO2 atmospheres delay induction and reduce the abundance of both transcripts. Reduced O2 and/or elevated CO2 atmospheres reduce C2H4 biosynthesis by delaying and suppressing expression of ACS at the transcriptional level and by reducing the abundance of active ACO protein. Chemical names used: 1-aminocyclopropane-1-carboxylic acid (ACC), ACC synthase (ACS), ACC oxidase (ACO), ethylene (C2H4), S-adenosylmethionine (AdoMet).
The capacity of ‘Eldorado’ pears to ripen increased dramatically after 4 weeks of exposure to 0°C and was associated with the synthesis of ethylene by pear tissue. Endogenous levels of ACC and internal ethylene were low after harvest, but increased rapidly after 4 weeks at 0°. Exposure to 0° for 4 weeks also resulted in an increase in soluble polyuronide during subsequent ripening at 20°. In contrast, after 9 months at 0°, soluble polyuronide content showed little increase when pears were transferred to 20°, and fruit failed to soften normally even though ACC content, internal ethylene concentration, ethylene evolution, and respiration remained relatively high. The content of arabinose, galactose, and rhamnose residues in cell walls decreased substantially during the ripening period after 4 weeks or longer at 0°. These cell wall neutral sugars decreased during ripening, even after 9 months of storage at 0°, while firmness and soluble polyuronide showed little change after fruit were transferred to 20°. These data indicate that the failure of pears to soften normally at 20° after prolonged storage at 0° is not related to ethylene synthesis or to changes in cell wall noncellulosic neutral sugar content, but is probably associated with mechanisms of polyuronide solubilization. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC).
‘Thompson Seedless’ fruits from vines that received gibberellin or auxin treatment were separated into different maturity classes and stored at 0° for 98 days. Samples were withdrawn at about monthly intervals and soluble solids, total acidity, malic acid, arginine and proline were measured. Fruits with differing soluble solids concn had the same soluble solids content per berry. After 30 days of storage, the soluble solids concn and total acidity of non-GA3 treated fruits began to increase, probably as a result of water loss. Malic acid concn and content increased for 30 days in storage, remained stable for the next 28 days, and then decreased during the remainder of the storage period. The amino acids, arginine and proline, remained relatively constant during the 1st 58 days of storage and then increased greatly both in concn and content.
Ozone treatment has many advantages for control of fungal diseases. There are no residue concerns, no registration is required, and it is non-specific, therefore potentially effective against a broad spectrum of pathogens. However, ozone is known to cause plant damage. There is little information available on either the ozone tolerance of floriculture crops or the levels required to kill plant pathogens under commercial conditions. Nine floriculture crops (begonia, petunia, Impatiens, Kalanchoe, pot roses, pot chrysanthemums, lilies, snapdragons and Alstroemeria) were subjected to increasing levels of ozone. Trials were conducted at 5 and 20 °C (90% to 95% RH) and ozone exposure was for 4 days for either 10 hours per day (simulating night treatment) or for 10 minutes every hour. Damage was assessed immediately after treatment and after an additional 3 days at room temperature in ozone-free air. Trials were terminated for the crop when an unacceptable level of damage was observed. Trials to determine the lethal dose for actively growing pathogens (Alternaria alternata, Alternaria zinniae and Botrytis cinerea) and fungal spores were conducted under identical conditions. Ozone tolerance varied with plant type and ranged between <0.2 and 3ppm. Generally, the crops surveyed were more susceptible to ozone damage at the low temperature. As a group, the bedding plants were the least tolerant. Fungal spores were killed at treatment levels between 0.8 and 2 ppm ozone. The actively growing fungal mycelium was still viable at 3 ppm ozone when the trial had to be terminated due to ozone-induced structural damage in the treatment chambers. Under the trial conditions, only the Kalanchoe would be able to tolerate the high levels of ozone required to kill the fungal spores.
shelf life ( Clark and Finn, 2008 ). For instance, many growers harvest early in the morning to minimize field heat and reduce the time before fruit is placed in cold storage. Some of the most common and potentially devaluing defects in blackberry fruit
could be determined shortly after harvest. However, the differences among cultivars regarding the degradation of fruit quality in shelf life conditions were not assumed to be the same as those in cold storage, which is the typical method of storage
‘Bosc’ pears (Pyrus communis L.) harvested at an optimum maturity, based on flesh firmness (about 62 N), were stored either in air or 1% O2 (plus <0.03% CO2) at −1°C. Fruit stored in air for 1 to 3 months softened rapidly after 2 days of ripening at 20°C and reached ripeness with flesh firmness of 20 N or lower by the 9th day. Ripening was associated with a reduction in extractable juice (EJ) and an apparent increase in water soluble polyuronides (WSP). Fruit stored in air for 4 to 5 months also softened rapidly after 2 days of ripening, but flesh firmness was still between 26 and 30 N after 9 days; however, EJ and WSP of fruit did not change appreciably during 9 days of ripening. The WSP content in fruit stored in either air or 1 % O2 increased substantially during 6 months of storage at −1°C. Increased WSP content during storage did not affect the quantity of EJ. Fruit stored at 1% O2 showed a reduction in EJ and an increase in WSP during the 9-day ripening period, whereas, in long-term air-stored fruit, EJ did not decline while WSP was degraded. Correlation of EJ and WSP during each ripening period provided an estimation of storage life. Increased WSP after ripening might be responsible for the increase in hygroscopic binding capacity of the ripened pulp tissue.
Two mild and two pungent onion (Allium cepa L.) selections (hereafter referred to as cultitypes), W420B, W424B, MSU8155B, and Exhibition, were grown at two locations in two states (Wisconsin and Oregon) during 1994 and 1995. Onion bulbs were harvested, stored at 4 °C and sampled for antiplatelet activity, pungency, and soluble solids 10 days after harvest and every 40 days during a 210-day postharvest storage period. Significant cultitype × state and cultitype × year interactions were detected. However, these were primarily due to the change in rank of cultitypes within the mild or pungent group. Averaged over all environments, antiplatelet activity was significantly greater in 1994 compared to 1995 for all cultitypes. Significantly greater antiplatelet activity was measured for three out of four cultitypes grown in Oregon compared to Wisconsin. During postharvest storage, antiplatelet activity increased 61% and 56% across all cultitypes and across both states during 1994, and across all cultitypes in Wisconsin during 1995, respectively. Although pungency determination can be a good indicator for relative rankings of different cultitypes for antiplatelet activity, changes in pungency were not correlated with changes in antiplatelet activity during postharvest storage. Results demonstrate cultitype, environment, duration of postharvest storage and genotype × environment interactions influence pungency, soluble solids, and antiplatelet activity, which should be considered when assessing onion-induced antiplatelet activity.
development and severity of CI in japanese plums based on the oxidative stress theory following time course analysis of enzymatic and non-enzymatic antioxidants in a multiple sampling framework. Materials and Methods Fruit material and cold storage. Japanese