MARKER-ASSISTED SELECTION IN STONE FRUITS

Molecular linkage maps in peach first appeared in 1994 and included markers associated with traits of horticultural interest, such as vegetative habit, fruit skin pubescence (fuzz), and red leaves.
Many breeders predicted a rapid development of marker-assisted selection (MAS), based on the analysis of markers closely associated with the character rather than the character itself, which is often not expressed in seedlings during their juvenile phase.
Since then, diverse molecular markers have been developed including: isozymes; RFLP; markers produced by means of PCR and arbitrary primers, such as RAPD and AFLP; markers based on length polymorphism of repetitive DNA, such as SSR; markers based on single point mutations such as SNPs and others obtained from either cDNA sequences (ESTs) or databases (CGAs, Cloned Genes Analogs). Different approaches to the analysis of marker-trait association include the use of mapping populations segregating for the characters of interest, bulk segregant analysis (BSA), and linkage disequilibrium (LD). The most important characters and quality trait loci (QTL) have been tentatively mapped in several stone fruits (peach, almond, cherries, common and Japanese apricot, and myrobalan plum). Some of them are used in early progeny screening, include blooming time, pollen sterility, self-incompatibility, double flower, fruit shape, skin hairiness, flesh color, acidity and sweetness, pillar and weeping tree architecture, red leaves, resistance to powdery mildew, leaf curl, root-knot nematodes and other pests and diseases.
There are many advantages offered by the high degree of genome synteny found in Rosaceae, which allows transferring sets of markers and coding sequences between species.