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  • Author or Editor: Paula Morales x
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Pruning and skirting (removal of low-hanging limbs) effects on canopy temperature, relative humidity (RH), and fruit yield and quality of `Orlando' tangelo trees (Citrus paradisi Macf. × Citrus reticulata Blanco) on `Carrizo' citrange rootstock [Poncirus trifoliata (L.) Raf. × Citrus sinensis (L.) Osb.] were studied at the Univ. of Florida Fifield Farm in Gainesville, Fla., in 1996–97. In the first season, treatments consisted of skirted and non-skirted trees. In the second season, two skirting (skirted and non-skirted) and three pruning (gable-top, flat-top, and non-pruned) treatments were evaluated. Neither RH nor air temperature was affected in the lower canopy by any treatment. However, temperature in the upper canopy of flat-topped trees was higher than that in gable-topped or non-pruned trees, and reached >45 °C during spring and summer. Fruit number and yield were decreased by pruning and skirting in one season. Skirted, gable-topped trees had the lowest yields, followed by skirted, flat-topped and non-skirted, gable-topped trees. All other treatments produced yields similar to those of non-skirted, non-pruned trees. Pruning increased the percentage of large fruit and reduced the percentage of small fruit. Skirting and pruning had no effect on blemish incidence with the exception of wind scar, which was higher in skirted than in non-skirted trees in the first season. During both seasons the main causes of packout reduction were rust mite and wind scar damage. Regardless of treatment, rust mite damage was much higher in the lower than in the upper canopy because of lower average temperatures and higher RH. Pruning effects on fruit quality were similar to those reported previously, but skirting had no effect on most fruit quality factors.

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Rain cracking (hereinafter referred to as macrocracking) severely impacts the production of sweet cherry (Prunus avium). Calcium (Ca) sprays can reduce macrocracking, but the reported responses to Ca sprays are variable and inconsistent. The objective of this study was to establish the physiological mechanism through which Ca reduces macrocracking in sweet cherry fruit. Six spray applications of 50 mM CaCl2 had no effect on macrocracking (assessed using a standardized immersion assay) despite a 28% increase in the Ca-to-dry mass ratio. Similarly, during another experiment, there was no effect of up to nine Ca sprays on macrocracking, although the Ca-to-dry mass ratio increased as the number of applications increased. In contrast, CaCl2 spray applications during simulated rain (in a fog chamber) significantly reduced the proportion of macrocracked fruit. Additionally, immersion of fruit in CaCl2 decreased macrocracking in a concentration-dependent manner. Monitoring macrocrack extension using image analysis revealed that the rate of macrocrack extension decreased markedly as the CaCl2 concentration increased. This effect was significant at concentrations as low as 1 mM CaCl2. Decreased anthocyanin leakage, decreased epidermal cell wall swelling, and increased fruit skin stiffness and fracture force contributed to the decrease in macrocracking. There was no effect of CaCl2 on the cuticle deposition rate. Our results demonstrated that Ca decreased macrocracking when applied to a wet fruit surface either by spraying on wet fruit or by incubation in solutions containing CaCl2. Under these circumstances, Ca had direct access to the cell wall of an extending macrocrack. The mode of action of Ca in reducing macrocracking is primarily decreasing the rate of crack extension at the tip of a macrocrack.

Open Access