Dissection of acidity-related traits in an apricot (Prunus armeniaca L.) germplasm collection revealed the genetic architecture of organic acids content and profile

Fruit acidity-related traits significantly influence consumer preferences for apricots (Prunus armeniaca L.). This study evaluated the variability associated with overall fruit acidity, and the content and profiles of ten organic acids (cis-aconitate, citrate, fumarate, galacturonate, malate, oxalate, quinate, shikimate, succinate and tartrate) separately in pulp and skin tissues across three consecutive harvesting seasons in an apricot germplasm collection. The phenotypic dataset was integrated with genotyping data from a customized 25K target SNPs assay to perform genome-wide association studies and complemented with linkage mapping in four segregating progenies. A major locus was identified on chromosome 8 (qMCr8.1) showing a Mendelian-like effect on the qualitative profile of malate and citrate, the most abundant organic acids in apricot fruits. This locus segregated accessions into three groups: citrate- or malate-predominant, or balanced. In contrast, the quantitative abundance of specific organic acids (OAs) and total OAs content (strictly correlated to titratable acidity) exhibited a more complex genetic architecture, controlled by several minor QTLs on different chromosomes, with significant seasonal variability and a strong correlation with maturity date. Beyond establishing the genetic determinants of fruit acidity traits, this study provides valuable insights for future implementation of marker and/or genomics-assisted approaches in apricot breeding.