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  • Author or Editor: Eugene Mielke x
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Abstract

Interstocks significantly affected β-carotene and lycopene in the pulp and peel of ‘Redblush’ grapefruit (Citrus paradisi Macf.) on Cleopatra mandarin (C. reshni Hort. ex. Tan.) rootstocks. Fruit from non-interstocked trees consistently had the lowest levels of both pigments. Trees wit Nasnaran (C. amblycarpa Ochse.) interstocks had consistently high levels of both pigments, particularly late in the harvest season.

Open Access

Abstract

The isozyme banding patterns of pollen enzymes make it possible to distinguish between the 4 principal cultivars of pecan (Carya illinoensis (Wang) K. Koch) grown in Arizona (‘Apache’, ‘Barton’, ‘Western Schley’ and ‘Wichita’). Although differences existed in all 3 enzymes asaayed (acid phosphatase (HP), glutamate-oxalacetate transaminase (GOT) and esterase (EST) only information provided by GOT and EST was necessary to distinguish between the 4 cultivars.

Open Access

Abstract

Levels of both free and bound abscisic acid (ABA) in flower primordia of ‘Montmorency’ sour cherry, as measured by gas-liquid chromatography (GLC), increased during autumn leaf abscission. Mechanical defoliation of trees prior to the onset of leaf abscission prevented this increase in ABA without affecting the intensity of rest. The leaves on forced branches inhibited neither bud break nor flower development, while ABA inhibited both processes. Once the level of ABA had risen naturally, temperature had no effect on its disappearance. These results cast doubt on the involvement of ABA in the control of winter bud dormancy in sour cherry.

Open Access

An assay for pyruvate kinase (PK) was tested as a diagnostic tool for cork spot, a major physiological disorder in pear Pyrus communis L. cv. d'Anjou) fruit. PK activity and Ca and protein concentrations were measured in peel of normal and affected fruit during selected months in 2 years. Protein concentration was more closely associated with cork spot than PK activity or Ca concentration. These preliminary results suggested the PK assay was a poor diagnostic tool for cork spot.

Free access

The effects of prohexadione-calcium (P-Ca) on fruit size and return bloom in three pear cultivars were evaluated in Medford and Hood River, Ore., and in Cashmere, Wash. A variety of treatment dosages and timings was applied to 4- and 5-year-old trees in 2 years of study. Fruit weight of `Bosc' and `Red Anjou' pears was not affected by P-Ca treatments at any location in either year. However, decreased weight of `Bartlett' pear fruit was associated with all P-Ca treatments in 1999 in Medford except for 83 ppm applied at 2.5 to 6.0 cm shoot growth (first treatment) plus 2, 4, 6, and 8 weeks after first treatment (WAFT) and 125 ppm applied at 2.5 to 6.0 cm growth plus 4 WAFT. `Bartlett' fruit weight was reduced in Medford in 2000 by all treatments except 125 ppm applied at 2.5 to 6.0 cm growth plus 4, 8, and 12 WAFT. In Cashmere in 2000, mean weight of `Bartlett' and `d'Anjou' fruit was reduced by treatments with 83 or 125 ppm applied at 2.5 to 6.0 cm growth plus 2, 4, and 6 WAFT and of `Bosc' pear by all treatments that included more than a single application of P-Ca. Crop load was not significantly different among treatments at any location. Return bloom in the year following P-Ca treatment was reduced in `Bosc' pears by some to most treatments at all locations in both years. In contrast, return bloom was reduced in `Bartlett' and `Anjou' pears only in Hood River in 1999.

Free access

`Columbia' and `Gebhard' strains of red `d'Anjou' pears (Pyrus Communis L.) harvested at similar maturity exhibited different ripening behavior after monthly removal from 1C storage in air. `Columbia' fruit produced ethylene at higher rates than `Gebhard' fruit during 15 days of ripening at 20C after each corresponding storage interval, `Gebhard' fruit required a longer period of chilling than `Columbia' fruit to generate noticeable rates of ethylene during ripening. The unripened fruit of both strains contained similar amounts of ACC at each corresponding storage interval. At each corresponding ripened state, ACC content in `Columbia' fruit increased 2 to 3-fold, while that in `Gebhard' fruit changed very little. After sufficient chilling, `Columbia' fruit were capable of softening to proper ripeness, and they developed buttery and juicy texture as indicated by the apparent reduction of extractable juice (EJ) content. `Gebhard' fruit also softened but to a lesser extent than `Columbia' fruit. Ripened `Gebhard' fruit had only slightly lower levels of EJ than unripened fruit and did not develop a buttery and juicy texture after any storage intervals. Titratable acidity (TA) in fruit of both strains varied between for the 1988 and 1989 seasons but decreased significantly during storage in both years. Soluble solids concentrations (SSC) in both strains also varied seasonally but did not change during storage or ripening. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC).

Free access

Relationships between mineral content and corkspot in `Anjou' pears (Pyrus communis) were evaluated in 1985 and 1986. Although there were no significant relationships between mean preharvest fruit mineraI content and corkspot incidence, the postharvest mineral concentrations of corkspotted and normal fruit were markedly different. Corkspotted and normal pear fruit had different Ca and N : Ca ratios in all types of subsamples (peels, opposing tangential slices with peels, opposing tangential slices without peels, cortical tissue plugs from the area next to the core, cortical tissue plugs from the area just inside of the peel, and the cores including seed), based on either dry or fresh weight. The dry-weight basis also revealed differences in Mg concentrations in both years and in B and K concentrations in 1986. Peel concentrations correlated with other tissues and were the easiest subsample to process. Corkspot was absent in either year, with a peel N: Ca ratio below 6.3. A computer model used mean Ca concentrations and standard deviations to estimate the percentage of pears in each orchard that were less than a given threshold level. When the overall average percentage of arbitrarily defined low-Ca pears was small (< 10%), it was difficult to predict the actual number of low-Ca pears from mean Ca concentrations. Therefore, it may not be realistic to expect strong correlations between mean Ca concentration and the incidence of disorders commonly encountered in Hood River, Ore. This situation occurred even when Ca concentrations of disordered and normal pears clearly differed.

Free access

`Bartlett' pears (Pyrus communis L.) were harvested at commercial maturity (average flesh firmness of 18 lb), stored at 30F for 0, 2, or 4 weeks, and then placed into a ripening room at 68F with or without ethylene to evaluate ripening activities. Pears that were stored in air at 30F for <4 weeks did not ripen after 7 days at 68F in an ethylene-free (no-ethylene) room. These pears ripened normally and uniformly after 7 days at 68F in a room enriched with 100 ppm ethylene (yes-ethylene). `Bartlett' pears that were stored in air at 30F for 4 weeks ripened normally after 5 days at 68F in the yes-ethylene room or 6 days at 68F in the no-ethylene room. The amount of cans produced per ton of fresh processed pears can be maximized most economically by exposing freshly harvested `Bartlett' pears to 100 ppm ethylene at 68F for 7 days before canning.

Full access

A proportion of `d'Anjou' pear fruit (Pyrus communis L.) developed a disorder, “black speck” or “skin speckling”, after prolonged controlled atmosphere (CA) storage (1% O2, - 0.5 C). A comparative study of biochemical components revealed that there was no significant difference in succinic, citric, fumaric, and pyruvic acids between the speckled' and normal skin tissues. The content of malic acid in the affected tissue was almost three times lower than that in the normal tissue. The specific activity of NADP-malic enzyme (EC 1.1.1.40) in the affected tissue was also lower, but the total activities were similar. The affected tissue contained higher percentages of dry matter and soluble proteins than the normal tissue. Two-dimensional gel electrophoresis of proteins showed that two groups of novel polypeptides appeared only in the affected skin tissue. This study indicated that a certain proportion of `d'Anjou' pear fruit might have been exposed to unfavorable preharvest environmental stresses, and, therefore, could no longer tolerate the subsequent semi-anaerobic and chilling stresses during prolonged CA storage.

Free access