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  • Author or Editor: Miklos Faust x
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Abstract

Russeting of apples in a humid environment is a major concern of fruit growers. In 1970 and 1971, two meetings were held in Pennsylvania exclusively to discuss this important problem. 3

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Abstract

Most of the important changes in the apple industry during the last century have resulted from State and Federal research. Methods have been developed for improvement of nutrition, protection from diseases and insects, extension of storage life, and long-distance shipment.

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Abstract

The fruit surface characteristics of 15 nectarine clones were examined by scanning electron microscopy at 200 and 2000× magnifications. The surface of nectarines appeared very different from surfaces of fruits previously examined. The relatively unprotected surface, the apparent ridging, and minute cracks starting at stomates of nectarines have not been previously described. Among clones, differences were evident in prominence and coarseness of ridges, number and elevation of stomates, and cracking of the cuticle of mature fruit. The appearance of minute cracks coincided with the time of natural brown rot infection; thus the cracks are regarded as the most likely entry sites for the brown rot organism. Stomates seemingly were suberized in maturing fruits. The study revealed that relatively small differences in surface structures are apparently heritable.

Open Access

Polyamine, putrescine, spermidine, and spermine contents were determined during endodormancy in the buds of low-chilling-requiring `Anna' apples (Malus domestics Borkh.). Putrescine, spermidine, and spermine contents increased greatly in buds when their chilling requirement was satisfied. Polyamine biosynthetic inhibitors α -difluoromethylarginine (DFMA) or α -difluoromethylornithine (DFMO) reduced bud break and bud growth in concert with decreased polyamine titers. DFMO or DFMA did not inhibit bud break when it was applied to buds after they received the full chilling requirement. DFMO was more inhibitory than DFMA. The polyamine requirement was much higher for bud growth and bud development than during differentiation and bud break.

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Ethylene biosynthesis and polyamine content were determined in normal and watercore-affected apple (Malus domestics Borkh. cv. Delicious). Fruit with watercore produced more ethylene and contained higher amounts of putrescine (PUT), spermidine (SPD), 1-aminocyclopropane-1-carboxylic acid (ACC), and 1-(malonylamino) cyclo-propane-1-carboxylic acid (MACC). The activities of ACC synthase and ethylene-forming enzyme (EFE) in watercore-affected fruit were also higher than in normal fruit. The EFE activity in severely affected flesh was inhibited, resulting in ACC accumulation and low ethylene production. S-adenosylmethionine (AdoMet) was maintained at a steady-state level even when C2 H4 and polyamides were actively synthesized in normal and affected fruit.

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Authors: and

Abstract

The vigor of growth and branching pattern of about 2000 apple seedlings were assessed. The seedlings were 8 years of age and were obtained by intercrossing 4 ‘Goldspur Delicious’ × ‘Redspur Delicious’ hybrids. The seedlings differed considerably in their vigor; the largest tree measured 16 times larger than the smallest one. The short internode condition seemed to exert some dwarfing effect on tree size but was not, however, the sole factor accounting for the degree of dwarfing observed. Measurements revealed that short internode conditions occurred within the most vigorous tree class as well as within the least vigorous one. A continuous variation rather than discontinuous segregation was observed with regard to both vigor of the trees and presence of spurs. Branching pattern also differed with the most numerous pattern being trees with upright branches, some of which produced only a limited number of third-order branches while the others produced a more pronounced number of second-order laterals. Trees with spread-shape crowns consisted of about 20% of the total count, while trees with natural-shape crowns, only 8%.

Open Access

Abstract

The growth curves of eastern-grown nectarines (Prunus persica (L.) Batsch) do not follow closely the three-phase sigmoid curve established for peaches. All clones completed phase I at the same time. However, many clones did not have a well-defined ‘final swell’ and several showed gradual increases in growth through phases II and III. Percentages of final fruit size attained during the final few weeks of growth or percentages of calcium in leaves, fruits or peels were not closely associated with cracking of fruits. Slower growth rate appears linked to the nectarine character, although the linkage seems to have been partially broken in some clones. Growth rates of 41 nectarine clones were not closely associated with field cracking or minor surface cracking.

Open Access

The ability of low and high temperatures and S-containing compounds to overcome endo- and paradormancy along with the possible mechanisms involved in these treatments for breaking `Anna' apple bud dormancy were studied. All three treatments induced budbreak in paradormant (July) and endodormant (October) buds. Cold, heat, and allyl disulfide increased ascorbic acid, the reduced form of glutathione (GSH), total glutathione, total nonprotein thiol (NPSH), and nonglutathione thiol (RSH), whereas dehydroascorbic acid and oxidized glutathione (GSSG) decreased. The treatments also increased the ratios of ascorbic acid: dehydroascorbate and GSH: GSSG and the activities of ascorbate free-radical reductase (AFR, EC 1.6.5.4), ascorbate peroxidase (EC 1.11.1.11), dehydroascorbate reductase (DHAR, EC 1.8.5.1), ascorbate oxidase (AAO, EC 1.10.3.3), and glutathione reductase (GR, EC 1.6.4.2) in the buds. These results indicate that budbreak induced by cold, heat, and allyl disulfide is associated with the removal of free radicals through activated peroxide-scavenging systems.

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The glycolipids, phospholipids, and sterols were determined in normal and watercore-affected apple (Malus domestica Borkh. cv. Delicious). Fruit with watercore contained higher amounts of glycolipids, phospholipids, and sterols. The ratios of unsaturated to saturated fatty acids and (18:3) to (18:1 + 18:2) were lower in watercore-affected tissue than in normal tissue. The ratio of free sterols to phospholipids was higher, whereas the ratio of phosphatidylcholine to phosphatidylethanolamine was lower in watercore-affected apple. Membrane lipids were altered in watercore-affected fruit.

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The changes of membrane lipids in apple (Malus domestics Borkh. cv. Delicious) auxillary and terminal buds from August to April were determined. The predominant lipids were monogalactosyl diglyceride (MGDG), digalactosyl diglyceride (DGDG), phosphatidylcholine (PC), and phosphatidylethanolamine (PE). An increase in membrane polar lipids was associated with budbreak and bud growth from August to April. Linolenic acid was the predominant fatty acid in MGDG, DGDG, and PC, while linoleic acid was predominant in PE. Phosphatidylglycerol (PG) and phosphatidylinositol (PI) contained a high amount of palmitic acid. The ratio of (18:2 + 18:3) to 18:1 fatty acids in galactolipids in apple buds increased from August to April. ß-Sitosterol and sitosteryl ester were the predominant sterols in apple buds. An increase in sitosterol, a decrease in sitosteryl ester, and a decline in the ratio of free sterols to phospholipids occurred during budbreak in spring. A decrease in sitosterol was associated with bud expansion in spring.

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