Development of diagnostic markers for selection of the subacid trait in peach

Peaches with low acidity are preferred in the market and this trait is usually selected in commercial breeding programs. A major gene (D/d) has been described for this character located on linkage group 5 of peach, where the low acid character is determined by the dominant D allele. In this paper, we analyze a collection of 231 varieties and 542 offspring to identify diagnostic markers for this character. The CPPCT040 single sequence repeat (SSR) is known to be tightly linked to D. We found that one of its alleles (193) is diagnostic for the subacid character and identified with high probability individuals with low acidity (titratable acidity <5.5 mg/l). The region around CPPCT040 was explored using 13 DNA fragments for a total of 5,297 bp, covering a length of 70.4 kbp of the peach genome. The sequenced fragments detected 19 single nucleotide polymorphisms (SNPs) and five indels. All subacid individuals shared a large haplotype (>24 kb) around CPPCT040, a region with higher than average SNPs between acid and subacid varieties. The CPPCT040 marker plus one of the SNPs identified (DH875) were used to genotype a collection of 542 seedlings, from different crosses expected to segregate for this character, which were phenotyped by tasting the fruit in the field. Data provided by both markers were always consistent and only 24 plants (4 %) did not fit the expectations. These markers and others that can be obtained from the haplotype identified can be readily used for marker-assisted selection in peach breeding.