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Victor Garcia de Cortazar and Gabino Reginato

Three different parameters were tested to estimate yield in `Royal Gala' apples. These are: a) parameters related to crop load—fruits per tree, fruits per cm2 of branch cross-sectional area, and fruits per hectare; b) parameters related with PFD interception: average fraction of PFD intercepted, total PFD intercepted during the season; and c) combination of the parameters a) and b). The data set was composed of measurements of PFD interception once a month and of yield components on various commercial apple orchards of the variety `Royal Gala' in the central zone of Chile between 2003 and 2006. The orchards were managed for high production, but there were differences of plantation distance, age, and size between them. Also, inside the orchard there were differences between trees. For the trees studied, there were variations of a factor of 10 for crop load, branch cross-sectional area, and tree size estimated as fractional interception of PFD at the beginning of the season. In spite of the big differences between trees, simple equations were fitted between yield and load parameters with coefficients of determination >0.95. Research funded by FONDECYT-Chile grant 1930695.

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Bruno Razeto, Gabino Reginato, and Sergio Rojas

Loquat (Eriobotrya japonica) belongs to the subfamily Pomoideae, and is an evergreen fruit tree which blooms in fall. Its inflorescence is a panicle. To attain commercial fruit size fruit thinning is done by hand. A chemical thinning trial was performed during the 1999-2000 growing season in Peumo, Cachapoal County, Sixth Region, Chile. Sixteen-year-old `Golden Nugget' loquat trees were treated with naphthalene acetic acid (NAA) at rates of 70, 140, and 280 g·ha-1 (1.0, 2.0, and 4.0 oz/acre), split into two or three applications beginning at early fruit set followed with sprays, 13 and/or 28 days later. Each treatment was applied to four randomly selected trees. At harvest, fruit number was measured in four panicles per tree and in the whole tree. NAA produced a thinning effect closely related to dose, with the highest doses inducing both highest flower thinning and the largest size of the fruit, but the lowest yield per tree. Lower doses produced fruit size and yield similar to those of hand-thinned check trees. Fruit load, expressed as trunk cross sectional area (TCSA), reached 1.8 to 9.1 fruit/cm2 TCSA (11.6 to 58.7 fruit/inch2 TCSA) in treated trees in comparison to 20 fruit/cm2 TCSA (121 fruit/inch2 TCSA) of the nontreated trees. NAA treatments did not affect the number of seeds per fruit. Total dose of 140 g·ha-1 NAA was the most effective in reducing fruit number, whether split into two or three applications. Fruit development seemed to conform to a double sigmoid curve, with a high rate of growth during fall, a lower one through the winter, in order to recover the growth rate in spring until maturity.

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Rodrigo Infante, Gabino Reginato, and Patricio Hinrichsen

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Gabino Reginato, Terence Robinson, and Victor Garcia de Cortazar

Several field experiments to assess the effect of tree size and crop load on fruit size and yield were conducted in a `Ross' cling peach orchard and in three nectarine orchards of different harvest seasons in Chile. Trees were randomly selected in each orchard and then hand-thinned at the beginning of pit hardening to a wide range of crop loads. The fraction of above-canopy photosynthetically active radiation intercepted by the canopy (PARi) was determined at harvest and all fruits were counted, weighted, and average fruit weight calculated. Cropload and yield were expressed in terms of fraction of PARi. Data on farm gate prices for export fruit of different sizes and export dates were obtained from a Chilean export company. For each orchard, the relationship between cropload and fruit size or cropload and yield efficiency was assessed by regression analysis. Fruit size distribution was calculated from adjusted fruit size assuming a normal fruit size distribution and valued according to shipment date and price. Using crop load as a covariate, fruit size adjusted for cropload was calculated for each nectarine orchard. Differences in adjusted fruit size and yield efficiency were detected among cultivars. Predicted crop value, normalized in terms of PARi intercepted, was calculated for all the cultivars. Large differences in predicted crop value were found for early, mid-season, and late-ripening nectarines. The early and late ripening cultivars showed the highest predicted crop value, especially at lower crop loads and larger fruit sizes. On the other hand, `Ross' cling peach showed its highest crop value at a medium crop load with high yield and relatively small fruit size. (Funded by FONDECYT grant 1930695.)

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Gabino H. Reginato, Víctor García de Cortázar, and Terence L. Robinson

Several field experiments to assess the effect of tree size and crop load on fruit size and yield efficiency were conducted in cling peach and nectarine orchards of different harvest seasons in Chile. Trees were randomly selected in each orchard and then hand-thinned at the beginning of pit hardening to a wide range of crop loads. The fraction of above-canopy photosynthetically active radiation (PAR) intercepted by the canopy (PAR i) was determined at harvest. All fruits were counted and weighed and average fruit weight calculated. Crop load and yield were normalized by tree size measured by intercepted PAR i. For each orchard, the relationship between crop load and fruit size or crop load and yield efficiency was assessed by regression analysis. Fruit size distribution was calculated from fruit size adjusted for fruit load assuming a normal fruit size distribution and valued according to shipment date and price obtained from a Chilean export company. Using crop load as a covariate, fruit size adjusted for crop load was compared for nectarine and peach cultivars. Fruit size adjusted for fruit load and yield efficiency was greater with late season cultivars than the early or midseason cultivars. Predicted crop value (PCV), normalized in terms of PAR intercepted, was calculated for all the cultivars. Large differences in predicted crop value were found for early, midseason, and late ripening nectarines. Early and late ripening cultivars had the highest predicted crop value, especially at lower crop loads and larger fruit sizes. The early season cultivars had high crop value as a result of higher fruit prices, whereas the late season cultivar had high crop value as a result of higher production. With cling peaches, the early season cultivar ‘Jungerman’ had a lower predicted crop value than the late season cultivars ‘Ross’ and ‘Davis’. For cling peaches, the highest PCV was achieved at a relatively high crop load with high yield and small fruit size.

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Catalina Pinto, Gabino Reginato, Karen Mesa, Paulina Shinya, Mariana Díaz, and Rodrigo Infante

The aims of this study were to characterize the softening rate of the flesh and some physiological parameters of three peach cultivars during the last phase of on-tree development. During two consecutive seasons, labeled fruits were nondestructively monitored on-tree, from the stone-hardening phase up to harvest. The absorbance index of the skin (I AD) follows a segmented, nonlinear regression. Beyond the intersection point of the two segments of the regression, the I AD decreased linearly at a higher rate 10 to 15 day before harvest. The most dramatic change of the I AD coincided with the “color break” of the skin. The I AD and the flesh softening were similar in ‘Andes Du-1’ and ‘Loadel’, while there was no difference in the growth rate of ‘Bowen’ and ‘Loadel’. ‘Andes Du-1’ and ‘Bowen’ showed the same growth rate in the upper and the lower sections of the canopy. The fruit at the upper section showed a mass of 30 to 50 g greater than the fruit at the lower section. In addition, no significant changes in the evolution of the soluble solids content (SSC) were observed, with the exception of ‘Loadel’ located in the upper section of the canopy. Differences in the length of the fruit development period are strongly influenced by the accumulated temperature after bloom. The difference in the fruit mass, SSC, I AD, and background color depend on the position of the fruit on the canopy. The use of mixed models, based on repeated sampling over time allows to accurately describing the evolution of peach ripening.