Mapping QTLs controlling fruit quality in peach (Prunus persica (L.) Batsch)

The organoleptic quality of fleshy fruits is in a large part defined by the ir composition of soluble sugars and organic acids. An F-2 population issui ng from a cross between two peach varieties,'Ferjalou Jalousia', a non-acid peach, and Fantasia, an acid nectarine, was analysed over 2 successive yea rs for agronomic characters and for molecular-marker (isoenzymes, RFLPs, RA PDs, IMAs and AFLPs) segregations. Blooming and maturity dates, as well as productivity, were noted for each tree. Four fruits per tree were analysed at maturity for fresh weight, colour, pH, titratable acidity, soluble-solid s content (SSC), acid (malic, citric and quinic acids) and sugar (sucrose, glucose, fructose, sorbitol) contents. QTLs were detected for all fruit com ponents analysed, except for fruit colour. The QTLs for nearly all componen ts were present on two linkage groups. For productivity, fresh weight, pH, quinic acid, sucrose and sorbitol content, all the detected QTLs displayed the same effect as the parental phenotypes. By contrast, for maturity date, titratable acidity, malic and citric acids and fructose, some QTLs display ed the same effect as the parental phenotypes while others displayed the op posite effect. The fraction of the total variation in each trait throughout the population explained by the QTLs was very high and reached more than 9 0% for some characters. For most of the characters analysed, epistasis was observed between QTLs.