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  • Author or Editor: Fabrizio Bucchi x
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Experiments were carried out for 3 years on `Gala' and `Fuji' apple cultivars. The efficacy of the compounds applied during blooming (ATS, Armothin) and at 10 mm king fruit diameter (BA, CPPU, and NAA) was studied. Results showed a poor efficacy of the chemicals applied during bloom, while compounds applied at fruit set showed interesting results. Among the new chemicals, citokinins were the most effective, although their effects were related to the cultivar: BA performs better than CPPU on `Fuji' while vice versa on `Gala'. In addition, both chemicals induced a slightly higher °Brix content, and acidity level showed the tendency to increase L/D ratio of the fruits as compared to controls. Fruit thinning and the strategies to enhance fruit size are applied early in the season and the problem remains, to assess their effectiveness as early as possible in order to adapt the management techniques (e.g., further thinning, if applicable, or fine-tuning of nutrition and irrigation, etc.) to enable the fruit to reach their maximum potential development. A modelling approach proposed by Lakso et al. (1995) postulates that apples grow in weight according to an equation termed “expolinear” (Goudriaan and Monteith, 1990) because after an initial phase of exponential growth (cell division), the apple enters a phase of linear growth (cell expansion) lasting up to harvest. The effectiveness of a thinning agent can therefore be evaluated-and explained-in terms either of the number of cells of the cortex tissue, or of their volume, or both. In addition, assessing the slope of the linear phase as early as possible might provide a prediction tool to evaluate size at harvest. This paper presents data from apple thinning trials on several cultivars. The effectiveness of these applications has been evaluated via an analysis of the cell parameters (number, volume and intercellular spaces) of the fruit's parenchyma cortex tissue. Also, fruit growth data have been used to test the possibility to predict fruit size at harvest once the fruit reaches the phase of linear growth.

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Prohexadione-Ca (Apogee®) was tested as a growth retardant and fire-blight control agent in the pear (Pyrus communis L. cv. Abbé Fétel) on both bearing trees in the orchard and on 1-year-old scions under greenhouse conditions. Four sprays of 50 and 100 mg·L-1 of the chemical were applied to trees in the orchard at 2-week intervals starting at petal fall, when terminal growth was 4 cm (mid-April). Scions received a single application (250 mg·L-1) and were transferred 2 weeks later to a greenhouse where the shoots were inoculated with a local, virulent strain of Erwinia amylovora (Burrill) Winslow et al. In the orchard, the higher prohexadione-Ca concentration was more effective in reducing shoot growth, enhancing fruit weight and controlling fire blight incidence and severity. Similar effects on growth parameters and disease progression were observed under greenhouse conditions. Chemical name used: calcium 3-oxido-4-propionyl-5-oxo-3-cyclohexene carboxylate (prohexadione-Ca)

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