Amy Iezzoni, Project Director, Michigan State University
Peach acidity is a key component of peach fruit flavor. Too much acid makes a fruit taste sour; too little and it tastes bland. Absolute levels of acidity and sweetness are important to flavor, but so is their balance. Developing peach cultivars with the desired levels and ratio of sugars to acid has long been a priority for peach breeders. While complex genetic control make this a highly challenging breeding objective, the international Rosaceae research community has made amazing progress to better understand sugar:acid factors and their interaction. We already know that a region on peach chromosome 4 contributes directly to flavor because it is associated with both sugar and acid levels (see Peach Flavor).
Recent studies have also identified two other chromosomal regions that influence peach acidity. A specific chromosomal region with a large effect on acidity was identified on peach linkage group 5 and is called the D locus (Boudehri et al. 2009). D was consistently associated with high (dd) and low (DD, Dd) acidity levels and a diagnostic marker was developed to ascertain its genotypic effect for any peach individual (Eduardo et al. 2014). In the RosBREED project, a second locus, named G7Flav, has also been identified. G7Flav explains a smaller but significant amount of phenotypic and genotypic variance for acidity (Fresnedo-Ramirez et al., 2015). Combining this new information generated by the international Rosaceae research community, we can now better predict acidity levels in any peach individual and have developed a single DNA test that genotypes both the D and G7Flav loci (called “Ppe-Acid”) for use by peach breeders worldwide. For details, see this page.
With this underlying genetic knowledge and the reliable Ppe-Acid DNA test, breeders can now plan crosses to maximize the probability of using parents with useful alleles and that are effective in combinations, identify superior seedlings with targeted levels of fruit acidity more efficiently, and deliver peach cultivars with wonderful fruit quality. Therefore, because knowledge of these genetic regions will lead to more effective breeding of peach cultivars, they are featured as two of RosBREED’s “Jewels in the Genome.”
Boudehri, K., Bendahmane, A., Cardinet, G., Troadec, C., Moing, A., Dirlewanger, E. 2009. Phenotypic and fine genetic characterization of the D locus controlling fruit acidity in peach. BMC Plant Biology 9:59.
Eduardo, I., López-Girona, E., Batlle, I., Reig, G., Iglesias, I., Howad W., Arús, P., Aranzana, M. 2014. Development of diagnostic markers for selection of the subacid trait in peach. Tree Genetics and Genomics 10:1695-1709.
Fresnedo-Ramirez, J., Bink, M.C.A.M., van de Weg, E., Famula, T.R., Crisosto, C.H., Frett, T.J., Gasic, K., Peace, C., Gradziel, T.M. 2015. QTL mapping of pomological traits in peach and related species breeding germplasm. Mol Breeding 35:166.