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  • Author or Editor: Francesco Marra x
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Rooted cuttings of Nemaguard peach [Prunus persica (L.) Batsch.] were grown in 0.18-, 0.36-, 0.90-, and 2.40-liter containers for 16 weeks to study the influence of root confinement on growth, gas exchange, water uptake, and leaf carbohydrate and nutrient content. An automatic nutrient-solution dispensing system was used to ensure uniform fertility among treatments and to prevent drought stress. Leaf area and stem length were reduced by root confinement 6 to 7 weeks after transplanting, and differences among treatments increased throughout the experiment. Final tree dry weights were reduced by 51% over a 13-fold reduction in rooting volume, but dry weight partitioning was largely unaffected. A temporary limitation to CO2 assimilation (A) and leaf conductance (g) was observed just after budbreak, but consistent reductions in A and g for confined trees did not occur until after week 11. Sorbitol and starch accumulated earlier in leaves of trees in smaller containers than larger containers. Despite similar fertility, concentrations of all nutrients except N and Cu were reduced ≈2-fold for trees in 0.18-liter containers compared to other treatments. However, characteristics of nutrient deficiency were not observed on any trees, and growth reduction with no change in leaf nutrient content was observed in other treatments. It was concluded that the initial mechanisms limiting growth were not gas exchange rates, levels of nonstructural carbohydrates, or drought stress, although nutrient deficiency may have contributed to growth limitation in trees with severely confined root systems.

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Peach trees trained to modified spanish bush (MSB) and Y-trellis (Y) were evaluated and compared in the Mediterranean settings of southern Italy. The observations included two peach (Rich May and Summer Rich) and two nectarine (Big Bang and Nectaross) cultivars. In the MSB system, trees were spaced at 4.5 × 2.5 m (888 trees/ha), whereas in the Y system, trees were spaced at 5.5 × 2 m (909 trees/ha). Costs at planting, yield per tree, fruit size grade, unit price of sold peaches for each size grade, amount and cost of materials and labor for cultural management, and grower’s profit were quantified throughout all 6 years from planting and at full crop (year 4–6). Fixed costs of the MSB system were 45% lower at planting, 11% lower for fertilization, and 33% lower for pest control than in the Y system. Regardless of cultivar, the MSB system reported 19% lower yields, 29% less management labor, and 12% higher labor efficiency (kg fruit/h) than the Y system. The yield gap between the two systems tended to decrease after the 5th year. A greater percentage of fruit fell into large size categories in the MSB than in the Y system. Fruit unit value and yearly profit were similar in the two systems. Even for the most profitable cultivar under the Y system (i.e., Nectaross), the time needed to pay off the additional investment for establishing a Y by its additional profit was ≈11 years, indicating an advantage of the Y system over the MSB only by the 12th year from planting. Yield trends, along with the high initial investment and management labor and costs in the Y system, indicate better financial performance and more sustainable production in the MSB than in the Y system.

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Canonical discriminant analysis (CDA) of morphometric data of buds, leaves, and fruit, as well as isozyme analysis (esterase, peroxydase, and acid phosphatase) of leaf samples, were used to identify eight male pistachio selections and 10 female pistachio cultivars. According to the CDA, 77% and 93% of the total variance was summarized by the first three canonical discriminant functions for the female and male selections, respectively. Fruit characteristics, particularly fruit fresh and dry weights and fruit length, accounted for most of the discriminatory power for the female cultivars, while the dimensions of the leaves, principally leaf rachis length, were the most effective discriminating characters for the males. Isozyme analysis showed a higher degree of polymorphism in the male than the female genetic pool. Hence, using only three enzymes, it was possible to identify all of the male selections, but only 50% of the females. Peroxidase polymorphism clearly demonstrated the greater phylogenetic distance between `Kerman' and the local cultivars, as well as between `Cerasola', a quite different cultivar with a reddish hull, and the others tested. The combination of CDA and isozyme analysis enhanced the possibility of uniquely identifying the female cultivars.

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