Saturating the Prunus (stone fruits) genome with candidate genes for fruit quality

To identify genes involved in the expression of a trait using the candidate gene (CG) approach, the genome positions of the maximum number of genes which potentially cause the observed phenotypic variability needs to be known. This position is compared with that of major genes or quantitative trait loci (QTL) for this character, with the co-location of the CG and major gene or QTL indicating a possible cause and effect relationship. In the present study we selected 273 sequences from expressed sequence tag collections, corresponding to CGs from metabolic pathways affecting fruit growth and maturity, texture, sugar and organic acid content, aroma and color, and mapped them in the Prunus reference map (T x E) based on an interspecific almond x peach F2 population. We used the bin-mapping approach, where only eight plants, six of the T x E progeny plus one of the parents and the F1 hybrid, are used to determine the position of a marker. This strategy was very efficient, with 206 CGs mapped, based mainly on the segregation of one or more single-nucleotide polymorphisms. These CGs were located throughout the Prunus genome and are a resource for genetic analysis in stone fruit (peach, plum, apricot and cherry) and almond. Co-locations between CGs and major genes or QTL responsible for natural variability of fruit quality characters in Prunus were identified using the available information on their positions.