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Shiow Y. Wang, Miklos Faust, and Michael J. Line

The effect of IAA on apical dominance in apple buds was examined in relation to changes in proton density (free water) and membrane lipid composition in lateral buds. Decapitation induced budbreak and enhanced lateral bud growth. IAA replaced apical control of lateral buds and maintained paradormancy. Maximal inhibition was obtained when IAA was applied immediately after the apical bud was removed; delaying application reduced the effect of IAA. An increase in proton density in lateral buds was observed 2 days after decapitation, whereas the change in membrane lipid composition occurred 4 days later. Removing the terminal bud increased membrane galacto- and phospholipids and the ratio of unsaturated to corresponding saturated fatty acids. Decapitation also decreased the ratio of free sterols to phospholipids in lateral buds. Applying thidiazuron to lateral buds of decapitated shoots enhanced these effects, whereas applying IAA to the terminal end of decapitated shoots inhibited the increase of proton density and prevented changes in membrane lipid composition in lateral buds. These results suggest that change in water movement alters membrane lipid composition and then induces lateral bud growth. IAA, presumably produced by the terminal bud, restricts the movement of water to lateral buds and inhibits their growth in apple.

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Lisa G. Neven

Organic production of pome and stone fruits in the United States has greatly increased during the past few years. To compete and enter lucrative export markets, these fruit must meet stringent quarantine requirements. For some countries, these requirements dictate that the fruit crops must be treated with a synthetic chemical fumigant, which is not compliant with organic standards. Therefore, nonchemical quarantine treatments for organically produced pome and stone fruits have been developed using the Controlled Atmosphere/Temperature Treatment System (or CATTS) technology. This technology applies a short-term heat treatment under a low-O2/high-CO2 environment, and is effective in controlling the most prominent quarantine insect pests while maintaining commodity quality. The technology has progressed beyond laboratory-scale research units to 1- to 2-ton commercial units. The development of these treatments and their effect on both insect mortality and commodity quality are discussed.

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Gerson R. de L. Fortes and Silvio L. Teixeira

The aim of this work was to study different apple of somatic material as callus and adventitious shoots are concerned, for further utilization in the research of somaclonal variation. The somatic materials were: leaf discs, cotyledons and hypocotyls of Gala apple seedlings, cultivated in a MS medium added by B5 vitamins in addition to (in mg/l): BAP (1,0), NAA (0,5) mio-inositol (100,0) sucrose (30,0 g/l) and solidified in agar (6,0 g/l). The several times of explant exposition to the dark affected the final callus weight. Callus weight derived from leaf discs were higher than those for cotyledons and hypocotyls. Explants exposed directly under light or up to two weeks in the dark showed less percentage of regenerative callus as compared to those of three weeks in the dark. The leaf explants presented the highest percentage of regenerative callus. The least response was obtained for those derived from hypocotyls. The highest number of adventitious shoots was obtained keeping the explants three weeks in the dark as compared to directed light exposition.

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Gerson R. de L. Fortes, Marisa de F. Oliveira, Nilvane T. G. Muller, Janine T.C. Faria, and Luciana B. Andrade

The apple crop in Brazil is established in acid soils with low pH. This condition leads to high aluminum levels in the soil. The aim of this work was to evaluate the callogenesis and organogenesis of apple rootstock somatic material under aluminum and different auxins concentrations. Internodes of apple rootstock cv. Marubakaido were inoculated in a MS medium containing aluminum (10 mg·L–1), BAP (5.0 mg·L–1), MS vitamins, myo-inositol (100 mg·L–1), sucrose (30 g·L–1), and agar (6.0 g·L–1). Picloram and NAA were tested at (0, 0.5, 1.0, 1.5, and 2.0 μM. Internodes were inoculated in test tubes and the whole material remained in dark for 3 weeks and then to 16-h photoperiod, 25 ± 2°C and 2000 lux. NAA-treated explants performed better than picloram ones. Callus intensity was maximized at 0.5 μM NAA. Although the higher percentage of callus formed (91%) occurred for NAA at 1.0 μM and 82% for picloram at the same concentration. NAA-treated explants responded for 62% of regenerated callus, while picloram presented only 6%. NAA also increased the mean number of shoots (3.54) and buds (11.52) as compared to picloram, which presented 1.40 and 2.78, respectively.

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Robert E. Call and Jack W. Jenkins

Mating disruption of codling moth using codlemone pheromoneemitting twist-ties or cards has become a standard practice in many orchards. This study was initiated to determine the effectiveness of NoMate CM EC, a spray formulation of codlemone pheromone. Treatments were applied 20–21 Apr. 1995 to plots measuring 99 × 244 m of 15-year-old `Golden Delicious' apple trees on seedling rootstock. Trees were spaced 3.7 × 5.5 m and treatments were made in a randomized complete block design replicated three times. Whole trees were sprayed to run-off using a handgun. Treatments were 20.2 g a.i. NoMate CM EC/h and a watered sprayed control. Two pheromonebaited, sticky traps were placed in each replicate to monitor codling moth activity. Moth counts were made 3 days after treatment and continued twice weekly for 4 weeks. Results indicated very little moth activity for the first 14 days of the study in plots treated with NoMate CM EC when compared to the control. However, after the first two weeks differences between treatments were not significant.

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F.F. Ahmed, A.M. Akl, A.A. Gobara, and A.E.M. Monsour

The beneficial effect on yield and quality of `Anna' apple fruits for the application of ascobine at 0.1% and citrine at 0.6% was studied during 1995 and 1996. Results showed that two citrine sprays at start of growth and 30 days later of ascobine at 0.1% or citrine at 0.6% were of material promotion effect on yield, fruit weight, total soluble solids, and total sugars, while reducing the total acidity. Both fertilizers were equally very effective in all the studied characters. The most striking and promising treatment was the application of ascobine at 0.1% or citrine at 0.6% twice during the growing season; i.e., growth start at 30 days later.

Open access

Raquel Gomez and Lee Kalcsits

‘Honeycrisp’ is among the most widely grown apple cultivars in the United States and ‘WA 38’ is a new apple cultivar released in Washington State. ‘Honeycrisp’ is highly susceptible to bitter pit and other physiological disorders; however, ‘WA 38’ is not susceptible to bitter pit but little is known about its susceptibility to other disorders. Bitter pit is a calcium-related disorder that has been associated with localized calcium deficiencies in fruit in addition to the proportions of calcium relative to the presence of other nutrients like potassium and magnesium. The objective of this study was to compare physiological differences and fruit quality between ‘Honeycrisp’ and ‘WA 38’ to determine how these differences might correspond to differences in mineral nutrient composition and bitter pit susceptibility. Here, ‘Honeycrisp’ and ‘WA 38’ elemental composition in leaves, fruit, and xylem sap was measured every 20 days starting 30 days after full bloom and compared with leaf gas exchange and stem water potential. ‘Honeycrisp’ had greater foliar transpiration rates that corresponded with greater calcium in the leaves and lower leaf K+Mg/Ca ratio, when compared with ‘WA 38’. In contrast, fruit calcium concentrations were higher for ‘WA 38’ with lower K+Mg/Ca ratios. Xylem conductance was higher during late summer in ‘WA 38’ compared with ‘Honeycrisp’. ‘WA 38’ fruit was denser than ‘Honeycrisp’ and more research is needed to determine whether differences in fruit structure may affect susceptibility to bitter pit in apple.

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Adriana C. de M. Dantas, Adriano N. Nezi, and Gerson R. de L. Fortes

Three different leaf segments (apical, basal, and middle) were treated in combination with aluminum at 0, 5, 10, 15 and 20 mg·L-1. Three kinds of leaf segments were inoculated in flasks in 12 replicates, with the adaxial surface touching the medium composed by basic macro- and micronutrient and MS vitamins added to 2,4-D (1.0 mg·L-1); BAP (5.0 mg·L-1); sucrose (30.0 g·L-1); myo-inositol (100.0 mg·L-1) and agar (6.0 g·L-1). The pH was adjusted to 4.0 before autoclaving. After inoculation, the explants were incubated in a dark growth room for 21 days and then, placed during 80 days, at 25 ± 2 °C, 16-h photoperiod provided by white fluorescent lamps under 19 μE·m-2·s-1 radiation. At the end of this period, the explants were evaluated. It was observed that basal leaf explants provided greener callus and that the heavier ones came from the middle leaf explants. Absence of Al or high Al concentrations favored the number of adventitious buds, whereas intermediate concentrations inhibited them. The absence of Al favored basal explants to form adventitious shoots, while lower concentrations favored apical and basal segments. High Al concentration appear to stimulate adventitious shoots in the basal and middle explants. Although it was evident that callus intensities were lower in higher Al concentration, Al is not so harmful to callogenesis and organogenesis.

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Yong-Koc Kim and Yong-Suk Kim

Experiments were carried out to evaluate some newly devised and conventional methods of grafting using `Fuji' apple trees on M.26/M. prunifolia rootstocks. Out of various methods of grafting, the modified inverted-veneer grafting and the inverted bark grafting showed a complete healing of the grafting union leaving no part of xylem tissue exposed in the air. However, owing to the longer period of growth for the trees grafted by the modified inverted-veneer grafting than the inverted bark grafting during the period of one growing season, the modified inverted-veneer gave slightly better shoot growth than the inverted bark grafting. It was clear that the former two methods were superior to the all other grafting methods, i.e., whip-and-tongue grafting, modified veneer grafting, inverted-veneer grafting, bark grafting, and chip budding in the grafting union healing, shoot growth, and tree form performance.

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Steven J. McArtney and Li Shao Hua

A single spray of either GA3 or GA4+7 at full bloom reduced the severity of the alternate bearing cycle of `Braeburn' apples, measured as the proportion of flowering spurs over the 2 years following treatment. Increasing the concentration of GA3 applied in the light-flowering year linearly reduced the proportion of flowering spurs in the following year and linearly increased the proportion of flowering spurs 2 years after treatment. Application of GA3 or GA4+7 at full bloom inhibited flower bud formation on spurs only, whereas, in a separate experiment, GA3 or GA7 applied later than 8 weeks after bloom inhibited flower bud formation on 1-year wood only. Thus, delayed GA treatments may provide suitable technology for the selective removal of fruit from 1-year wood in apple.