Abstract
This study aimed to determine the number of measurements necessary to evaluate physical and chemical characteristics of peach fruits, study the relationships between them and their direct and indirect effects on the content of ascorbic acid and total carotenoids. The characteristics skin and pulp color, fruit weight, suture, equatorial and polar diameters, firmness, soluble solids (SS), titratable acidity (TA), SS/TA ratio, ascorbic acid and total carotenoids were evaluated in 39 cultivars of peach and 3 cultivars of nectarine from the orchard of the Universidade Federal de Viçosa. The repeatability coefficient was estimated by ANOVA and CPCOR. Phenotypic correlation coefficients (rf) were estimated and, after the multicollinearity diagnostics, they were unfolded to direct and indirect effects of the explanatory variables on the response variable using path analysis. There was agreement on the magnitude of repeatability coefficients obtained by the two methods; however, they varied among the 14 characteristics. The highest correlations were found between FW, SD, ED and PD. Seven fruits are sufficient to evaluate the physical and chemical characteristics of peach with a correlation coefficient of 90%. The characteristics considered in the path diagrams (b* skin, hº skin, b* pulp, hº pulp, ED, PD, FIR, SS, SS/AT and TC) are not the main determinants of the ascorbic acid. The yellow hue of the pulp (hº pulp) has the potential to be used in indirect selection for total carotenoids.
Highlights
In conducting agricultural experiments various factors like climatic conditions, labor and financial resources, if limiting, complicate the measurement of many characters in many plants
The repeatability coefficients estimated by ANOVA were always lower or equal to those obtained by CPCOR (Table 1)
Results obtained by Nunes et al, (2004) with acerola indicated the variable titratable acidity (TA) as the main determinant of vitamin C content, contradicting the results presented by Gomes et al (2000), who recommended the selection based on SS for gains in vitamin C in acerola
Summary
In conducting agricultural experiments various factors like climatic conditions, labor and financial resources, if limiting, complicate the measurement of many characters in many plants. Measurement of these characters through samples is a procedure used in these experiments. Understanding the relationship between variables is crucial, since obtaining genetic gains and choosing the best genotypes are often directed to a set of agronomic and commercial variables Knowledge of these relationships allows the selection of a response variable with low heritability and/ or difficulty to measure on the basis of other (s) variable (s), enabling the breeder to obtain more rapid progress in relation to the use of direct selection
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