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 F-1 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.