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Variability in fruit quality of citrus occurs among and within trees due to an interaction of several factors, e.g., fruit position, leaf: fruit ratio, and fruit size. By determining variability in fruit quality among i) fruit, ii) trees, iii) orchards, and iv) geographic locations where citrus is produced in Florida, optimal sample size for fruit quality experiments can be estimated. To estimate within-tree variability, five trees were randomly selected from each of three `Valencia' orange orchards in four geographic locations in Florida. Six fruit were harvested from each of two tree canopy positions, southwest top and northeast bottom; fruit were not selected or graded according to fruit size. °Brix and titratable acidity of juice samples were determined, and the °Brix: acid ratio was calculated. Statistical analysis of fruit quality variables was done using a crossed-nested design. The number of trees to sample and the number of fruit per sample were calculated. To estimate between-tree variability, 10 trees were randomly selected from each of three `Valencia' orange orchards from four geographic locations in Florida. Fifty-fruit composite samples were picked from around the tree canopy (0.9 to 1.8 m). Juice content, SSC, acid content, and ratio were determined. Using a nested design, the number of orchards and number of trees to sample were determined. There was greater variability in fruit quality among trees than within trees for a given canopy position; the optimal sample size when taking individual fruit samples from a given location and canopy position is four fruit from 20 trees. There was less variability in fruit quality when 50-fruit composite samples were used, resulting in an optimal sample size of five samples from three orchards within each location.
Sources of variation in juice quality of `Valencia'sweet orange [Citrus sinensis(L.) Osb.] were quantified and their relative contributions to variability in juice quality were determined, from which sample sizes were estimated. Commercial orchards of `Valencia' sweet orange trees on Carrizo citrange [C. sinensis × Poncirus trifoliata (L.) Raf.] rootstock were selected at four geographic locations representing the major citrus-producing regions in Florida. Within- and between-tree variation in soluble solids concentration (SSC) and titratable acidity (TA) were estimated in two experiments over two or three seasons, respectively. Variance components for all treatment effects were estimated to partition total variation into all possible component sources of variation. Seasonal variation in SSC and TA was relatively small, but larger for TA than SSC. Variation in SSC among blocks within a location was intermediate to low, and was less than variation among locations. In contrast, tree-to-tree variation in SSC and TA was large, in spite of sampling from trees of similar vigor and crop load, and variation in SSC and TA among fruit was relatively large. Based on results of this study, samples consisting of 35 fruit are required to detect differences (P ≤ 0.05) of 0.3% SSC and 0.06% TA, whereas 20-fruit samples can be used to detect differences of 0.4% SSC and 0.08% TA. Seven replications are required to detect differences of 0.5% SSC and 0.1% TA, with small gains in precision when tree numbers exceed 10.
Abstract
The changes of amino acid compositions of peach proteins from the Alcohol Insoluble Solids of peaches (Prunus persica (L.) Batsch cvs. Redhaven and Redskin at 5 stages of maturation were investigated by gas-liquid chromatography. Most amino acids in the peach proteins showed gradual increases, as percent of total amino acid, throughout the maturation periods except aspartic acid in both peach cultivars and arginine in the ‘Redskin’ peaches. The amino acid profiles of the ripe fruits from both cultivars were nearly identical.