Analysis of genotypic variation of sugar and acid contents in peaches and nectarines through the Principle Component Analysis

Genotypic variations and correlations were estimated for sugar and acid contents on a fresh flesh weight basis in peach and nectarine genotypes derived from a clone of a wild peach (Prunus davidiana) by three generations of crosses with commercial nectarine varieties. 107 genotypes were studied in Avignon ( France), 40 in Gotheron (France), and 18 of them were common to both locations. Considerable variations in sugar and acid contents were found among genotypes in both locations. Though location significantly affected sucrose, sorbitol and acid contents of the 18 common genotypes, principal component analysis (PCA) indicated that genotypic correlations among sugar and acid contents were stable in both locations. Almost all sugars and acids analysed exhibited positive loadings for the first principal component (PC). Variations of dry matter content among genotypes only partially explained this general trend as shown by the PCA on a dry flesh weight basis. Glucose and fructose contents were closely correlated and were similar in amount in most genotypes, while fructose content was lower than glucose content in about 12% of the genotypes. A positive but loose relationship was found between malic and citric acid contents in both locations. Likewise, sucrose, sorbitol and quinic acid contents were positively associated. The first PC could be used as a general flavour component. In addition, three groups of closely associated variables (fructose and glucose; malic and citric acids; sucrose, sorbitol and quinic acid) were detected through PCA.