Search Results

You are looking at 1 - 9 of 9 items for

  • Author or Editor: E. Cohen x
Clear All Modify Search

Abstract

The total amounts of pectic fractions in the albedo tissue of infected and uninfected fruit of lemon [ Citrus lemon (L.) Burm.] were almost the same, but changes were found in different fractions: the water-soluble pectic fraction decreased in the infected fruit, while the alkali-soluble fraction increased and the acid-soluble fraction remained unchanged. Such changes in pectic substances may be typical of fruits exhibiting a firm type of rot.

Open Access
Authors: , , , , and

`Oroblanco' is an early-maturing pummelo-grapefruit hybrid (Citrus grandis × C. paradisi). The fruit of this cultivar are usually picked in October and are marketed while their peel color is still green. However, during long-term storage, the fruit turns yellow, and loses much of their commercial value. In a previous study, we found that application of gibberellic acid and low storage temperatures of 2 °C (35.6 °F) markedly reduced the rate of degreening. However, `Oroblanco' fruit are sensitive to chilling injuries, and thus could not be stored at 2 °C for long periods. In the present study, we examined the possible application of intermittent warming (IW) and temperature conditioning (TC) treatments, in order to retain the green fruit color during long-term cold storage but without enhancing the development of chilling injuries. It was found, that following storage at 2 °C, either with or without IW and TC, the fruit retained green color up to 16 weeks, whereas at 11 °C (51.8 °F) fruit turned yellow after 8 weeks. However, untreated fruit held continuously at 2 °C developed 40, 51, and 68% chilling injuries after 8, 12, and 16 weeks, respectively. IW (storage at cycles of 3 weeks at 2 °C + 1 week at 11 °C) reduced the amount of chilling injuries to only 5, 7 and 11% after the same periods of time, respectively. TC [a pre-storage treatment for 7 days at 16 °C (60.8 °F) before continuous storage at 2 °C] effectively reduced the development of chilling injuries to only 5% after 8 weeks of storage, but was ineffective in reducing chilling damage after longer storage periods. Because chilling damaged fruit is prone to decay, the IW and TC treatments also reduced the incidence of decay development during storage. The IW and TC treatments did not affect juice total soluble solids and acid percentages, but did affect fruit taste and the amounts of off-flavor volatiles emitted from the juice. Taste panels indicated that the taste score of untreated control fruit stored at 11 °C gradually decreased during long-term storage, and that this decrease was more severe in chilling damaged fruit stored continuously at 2 °C. The taste of IW-treated fruit remained acceptable even after 16 weeks of storage, and TC-treated fruit remained acceptable for up to 12 weeks. Fruit taste scores were inversely correlated with the concentrations of ethanol and acetaldehyde detected in the juice headspace.

Full access

Water loss was found to be a nondestructive indicator before visible symptoms of chilling injury (CI) in cold-stored grapefruit (Citrus paradisi Macf.) and lemon (C. limon L. Burm. f.). The water-loss rate increased significantly after removing the fruit from cold storage and holding at 20C. Scanning electron microscopy revealed large cracks around the stomata. Changes in electrical conductivity of the flavedo tissues, total electrolyte leakage, and K+ or Ca2+ leakage were all inadequate predictors of CI, appearing only after CI was evident.

Free access

Abstract

Nucellar and zygotic offspring of ‘Satsuma’ mandarin (Citrus reticulata Blanco) were differentiated by gas chromatographic analysis of gaseous emanations from fragmented leaves of 6-month-old seedlings. Analysis was rapid (< 3 minutes/sample), could be performed on individual leaves, and required virtually no tissue processing. Thus, the method is amenable to the screening of large progeny at the young seedling stage.

Open Access

Recently, yellows diseases have become more common in Israel, and phytoplasmas have been detected in some of these diseased crops. Commercial fields of two celosia species (Celosia plumosa L. and C. cristata L.) also have exhibited yellows symptoms and total crop failure. Typical mycoplasma-like bodies were observed in infected but not in healthy plants. The same plants were analyzed for the presence of phytoplasma by polymerase chain reaction (PCR), using the universal oligonucleotide pair r16SF2/r16SR2, followed by nested PCR using group-specific primers. Restriction analyses performed with these products indicated that two different types of phytoplasmas are infecting celosia. PCR-RFLP analysis of one type revealed a restriction pattern typical of aster yellows. Similar analysis of the second type indicated possible relatedness, though not identity, to the pattern of phytoplasmas of the Western-X group. This is, to our knowledge, the first report of phytoplasma infection in celosia.

Free access

Abstract

Resistant reaction types (RT) can be used to evaluate objectively downy mildew resistance on muskmelon foliage. Reaction types 2, 3, and 4 represent increasing levels of resistance compared to the susceptible reaction typified by RT 1. A double-digit classification system for the RT of leaves 1 and 2, respectively, in greenhouse–growth chamber inoculations of two-leaf stage plants is an excellent predictor of the disease reaction of older plants under field conditions. Spore production decreases progressively as the levels of resistance represented by RT 2, 3, and 4 increase.

Open Access

`Eureka' lemons [Citrus limon (L.) Burro. f.] treated for commercial storage were held for 6 months at 13C. One-half of the fruits were individually sealed in high-density polyethylene (HDPE) plastic film and half not sealed. The HDPE-seaIed lemons showed little change in the water relations characteristics, while unsealed lemons lost weight and decreased in water potential throughout the storage period. The maturity indices in the two treatments were generally similar during the first 3 months of storage, after which maturation of wrapped fruit was slower than that of the control. The overall marketable quality of the fruit was higher in HDPE-sealed lemons than in unsealed. From these results, it appears feasible to introduce seal packaging in packing lines where lemons will be placed in extended storage.

Free access

We are interested in identifying and isolating genes which affect the rate of softening in peach fruit. It may be possible through the engineering of these genes to delay or extend the softening. This could ultimately allow for the harvest and transport of more mature, higher quality fruit. The clone, pch313, was isolated from a ripe peach fruit cDNA library. RNA homologous to this clone is detected at a low abundance in fruit until softening when a >100 fold increase in abundance of the RNA occurs. Pch313 RNA is also detected 30 min after wounding leaf or fruit tissue and peaks in accumulation within 2-8 hours. Wound ethylene was measured from the same tissue and its rate of evolution paralleled the accumulation of the RNA. The cDNA was sequenced and found to have 78% sequence identity with pTom13, a tomato gene that is expressed during fruit ripening and wounding (Holdsworth et al., NAR 15:731-739, 1987). To determine the universality of pch313 related gene expression, RNA accumulation was measured in other fruits during softening, and in leaf tissue upon wounding.

Free access

We are interested in identifying and isolating genes which affect the rate of softening in peach fruit. It may be possible through the engineering of these genes to delay or extend the softening. This could ultimately allow for the harvest and transport of more mature, higher quality fruit. The clone, pch313, was isolated from a ripe peach fruit cDNA library. RNA homologous to this clone is detected at a low abundance in fruit until softening when a >100 fold increase in abundance of the RNA occurs. Pch313 RNA is also detected 30 min after wounding leaf or fruit tissue and peaks in accumulation within 2-8 hours. Wound ethylene was measured from the same tissue and its rate of evolution paralleled the accumulation of the RNA. The cDNA was sequenced and found to have 78% sequence identity with pTom13, a tomato gene that is expressed during fruit ripening and wounding (Holdsworth et al., NAR 15:731-739, 1987). To determine the universality of pch313 related gene expression, RNA accumulation was measured in other fruits during softening, and in leaf tissue upon wounding.

Free access