Application of Simple Sequence Repeat Markers for Fruit Soluble Solids Content and Titratable Acidity in the Arkansas Peach and Nectarine Breeding Program

Peach [Prunus perisca (L.) Batsch] is the third-most important temperate tree fruit crop produced in the world. It is a diploid species that belongs to the Rosaceae family. Fruit quality characteristics such as flavor, acidity, color, flesh texture, size, shape, and shelf life are important attributes on which breeding programs focus to produce new and improved peach cultivars. The Arkansas peach and nectarine breeding program, which started in 1964, was initially focused on clingstone, non-melting, yellow-flesh peach cultivars destined for the baby food industry. In recent years, the objectives of the program have changed to breeding fresh-market cultivars with different textures, flavors, flesh and skin colors, and harvest date. Soluble solids content (SSC) and titratable acidity (TA) are two important components of flavor, and within the Arkansas breeding program a wide range of peach SSC and TA is present. As part of the RosBREED project (www.rosbreed.org), phenotypic and genotypic data were collected on important Arkansas peach breeding program germplasm for 2010, 2011, and 2012, with the objective of implementing marker-assisted breeding (MAB) to complement the traditional breeding process. The simple sequence repeat (SSR) markers BPPCT015a for SSC and CPPCT040a for TA were screened on 127 trees of five different populations and their parents. This was the first use of these markers in the program. The SSC values varied from 11.2 to 29.6 °Brix and averaged 16.1 °Brix in the years analyzed. Six different alleles were identified for SSC. Of these, allele 168 was present in 84% of the trees analyzed. The average content of malic acid was 0.5 g/100 mL with a maximum value of 1.1 g/100 mL and a minimum of 0.2 g/100 mL. For this trait, four different alleles were identified, with allele 312 present in 82% of the analyzed individuals. These promising results will foster future studies focused on developing more accurate DNA markers for these traits and expand the application of MAB in peach breeding programs.