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Duane W. Greene

Over 225 apple cultivars grown at the Horticultural Research Center in Belchertown have been evaluated for fruit quality and fruit characteristics. Methods used to determine fruit characteristics and organoleptic assessment will be presented. The postharvest potential of the most promising apples will be presented. Two apples ripen about the first of September and show promise for early market. `Sansa' is a medium-sized red apple that ripens about the first of September. It is a high-quality apple with characteristics similar to `Gala'. `Ginger Gold' is a large, firm, mild-flavored, russet-free, yellow apple. `Honeycrisp' is a red apple that ripens in mid-September, before `McIntosh'. It is a large, mild-flavored apple that is sometimes erratic in red color development. It maintains firmness and explosive crispness out of storage better than any other apple evaluated. `Golden Supreme' is an extremely attractive, russet-free `Golden Delicious' type ripening 7 to 10 days before `Golden Delicious'. When ripe it has a very aromatic, fruity flavor. It stores better than `Golden Delicious'. Other apples with merit that have commercial potential include: `Hampshire', `Shizuka', `Cameo', `Creston', `Coop 25', `Coop 29', and `Braeburn'. `Pink Lady' is a very late maturing, new cultivar that is being heavily planted in other areas. Although it does mature here, based upon starch rating, fruit size is small, the flesh is dry and very tart, and taste is only fair.

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Duane W. Greene

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Duane W. Greene

Experiments were conducted to evaluate abscisic acid (ABA) and the combination of ABA and benzyladenine (BA) as a thinner on ‘Bartlett’ pears. Application of 500 mg·L−1 ABA at bloom, petal fall, and at the 10-mm stage resulted in significant fruit thinning at all timings. Application at the 10-mm stage nearly defruited the trees. Rates of ABA between 50 and 500 mg·L−1 were evaluated at 10 mm and the thinning response was quadratic and highly significant. Rates as low as 50 mg·L−1 thinned. BA at 150 mg·L−1 at the 10-mm stage did not thin and when combined with 250 mg·L−1 ABA, no additional thinning was observed, but extensive thinning was done by the ABA alone. When thinning with ABA was achieved, return bloom was also enhanced. Thinning with ABA generally resulted in larger fruit, greater flesh firmness, and higher soluble solids. The russet seen on ABA-treated fruit was attributed primarily to the surfactant used. Extensive leaf yellowing and leaf abscission were noted after ABA application, especially with the 250 mg·L−1 and 500 mg·L−1 and this was considered commercially unacceptable. BA was unable to reverse or modify the leaf yellowing and abscission caused by ABA as it has been shown to do with other plant species.

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Duane W. Greene

`Gardiner Delicious'/MM.lO6 apple (Malus domestics Borkh.) trees were initially sprayed in 1985 with paclobutrazol (PB) at 250 mg.liter-1 at tight cluster and again on 10 and 25 June and 29 July. From 1986 through 1988, PB sprays of 85 or 100 mg·liter-1 were applied at either petal fall (PF) + 2 or PF + 4 weeks and one to two additional sprays were applied per year when growth resumed. Promalin was applied to one group of trees that received PB starting at PF + 2 weeks. PB reduced terminal, lateral, and total shoot growth the year of application and in subsequent years. Although average shoot length of lateral and terminal shoots was reduced, the greatest reduction in growth occurred because PB prevented spurs from growing into lateral and terminal shoots. Compared to unsprayed trees, PB reduced pruning time in all 4 years by 23% to 70%. PB increased bloom only the first year after application, but increased fruit set for 2 years due to a carryover effect. Application of PB in 1985 caused a reduction in fruit size, sometimes in soluble solids concentration, length: diameter (L : D) ratio, and pedicel length. Promalin either overcame the reduction in the ratio or increased it in 1986. Reduced rates of PB in subsequent years caused few adverse effects on the fruit. PB increased flesh firmness when applied at PF + 2 weeks but not at PF + 4 weeks. Trees treated with PB produced fruit with higher flesh Ca and less bitter pit, cork spot, and senescent breakdown following regular air storage. Chemical names used: ß -(4 -chlorophenyl)methyl α -(1,1-dimethylethyl) -1H-l,2,4-triazole-1-ethanol (paclobutrazol, PB); gibberellins A4+7 plus N-(phenylmethyl) -1H-purine-6-amine (Promalin).

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Duane W. Greene

A range of concentrations and timings of CPPU application were evaluated in attempt to identify situations in which fruit size, flesh firmness, and soluble solids could be increased while minimizing increased incidence of fruit asymmetry and reductions in flower bud formation and fruit surface red color on 'McIntosh' apples (Malus×domestica Borkh.). The greatest response to CPPU for most attributes evaluated occurred when it was applied at fruit size between 6 mm and 16 mm. The conclusion from this series of experiments is that differential response to CPPU could not be established by altering the time of application. The response to CPPU is linear with increasing concentration. Results suggested that use of 4 to 6 mg·L-1 CPPU on apples to increase fruit size was the maximum and appropriate range to use without causing fruit asymmetry. Chemical name used: N-(2-chloro-4-pyridyl)-N′-phenyl urea (CPPU)

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Duane W. Greene

Pome fruit display a biennial bearing tendency that is characterized by heavy flowering and fruit set one year followed by a year with reduced bloom and fruit set. This tendancy results in a year with heavy cropping with small fruit, and a subsequent year with large fruit and a small crop. Both situations are undesirable. Chemical thinners in the “on” year are frequently used to modify this cropping behavior. Alternative methods to control cropping by flower bud inhibitions will be discussed. Gibberellin application in the “off” year at or soon after bloom will inhibit flower bud formation and encourage moderate flowering. This method of crop regulation has been used infrequently. Gibberellins differ in their ability to inhibit flowering. Therefore, selection of a specific gibberellin and an effective concentration range may provide greater flexibility in controlling flowering. The cytokinins CPPU and thidiazuron inhibit flower bud formation, increase fruit size, and also thin fruit. Appropriate application of these cytokinins will be discussed where beneficial effects on fruit size may be achieved while maintaining a moderate level of flower bud formation.

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Duane W. Greene

Proheaxadione-calcium (ProCa) was applied to `Spencer' apple trees at rates between 250 to 750 mg·L–1 after harvest but before leaf fall. The following spring terminal growth was reduced linearly from early petal fall through the growing season to leaf fall. ProCa was applied after harvest and before leaf fall at 500 mg·L–1 to `Spigold' apples. The carryover effect on terminal growth persisted for about 2 weeks after bloom. A combination of 500 and 82.5 mg·L–1 ProCa on `Spigold' in the fall and spring, respectively, reduced terminal growth greater than the individual treatments for about 3 weeks after petal fall. Recent report have shown that ProCa can induce physiological resistance to fire blight and apple scab when applied near petal fall. These data support the suggestion that ProCa may be used as a fall application and the carryover effects may result in early growth control. Potential benefits of the carry-over effects of ProCa for early-season suppression of fire blight and apple scab are discussed.

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Duane W. Greene