Mapping major genes and quantitative trait loci controlling agronomic traits in almond

Six tree traits (self-compatibility, blooming date, blooming density, productivity, leafing date and ripening time) and five pomological traits (kernel taste, in-shell weight, shell hardness, kernel weight and double kernel) were studied in an F₁ almond progeny of 167 seedlings from the cross between the French cultivar 'R1000' and the Spanish cultivar 'Desmayo Largueta'. In addition, a set of 135 codominant microsatellites or simple-sequence repeat (SSR) markers developed from peach, cherry and almond were used for the molecular characterization of the progeny. A genetic linkage map was constructed with 56 of these SSRs. Cosegregation analysis allowed the identification of the map positions of two major genes to be confirmed for kernel taste ( Sk ) in linkage group five (G5) and for self-incompatibility ( S ) in G6. QTLs mapped include two for leafing date ( Lf-Q1 and Lf-Q2 ) in G1 and G4, one for shell hardness ( D-Q ) in G2, one each for double kernel ( Dk-Q ) and productivity ( P-Q ) in G4, one for blooming date ( Lb-Q ) in G4, two for kernel weight ( Kw-Q1 and Kw-Q2 ) in G1 and G4, and two for in-shell weight ( Shw-Q1 and Shw-Q2 ) in G1 and G2. Four SSR loci (BPPCT011, UDP96-013, UDP96-003 and PceGA025) were linked to the important agronomic traits of leafing date, shell hardness, blooming date and kernel taste. Finally, the development of efficient marker-assisted selection strategies applied to almond and other Prunus breeding programmes was also discussed.