RAPD and AFLP tagging and mapping of Beta (B) and Beta modifier (MoB), two genes which influence β-carotene accumulation in fruit of tomato (Lycopersicon esculentum Mill.)

The Beta (B) locus in tomato (Lycopersicon esculentum) increases fruit beta-carotene content at the expense of lycopene, resulting in orange-pigmented fruit. Expression of B is influenced by the beta-modifier (Mo-B) gene which segregates independently of B. RAPD and AFLP analyses were performed using near isogenic lines : for B and bulked segregant analysis (NILs) unique (BSA) of a L. esculentumXL. cheesmanii-derived F-2 population segregating for B. Using 1018 random primers for RAPD analysis and 64 primer pairs for AFLP analysis, we identified polymorphic products which distinguished the NILs and the two bulked DNA samples constructed for BSA. A single 100 bp AFLP amplification product (E-ACA/M-CTG(100)) which distinguished the NILs cosegregated with MOB and was demonstrated to be tightly linked to the locus. E-ACA/M-CTC100 exhibited a recombination frequency of 1.7% in the F-2 progeny derived from an initial cross between the isolines. The Mo-B locus was mapped to the long arm of chromosome 6. Two RAPD products (OPAR18(1100) and UBC792(830)) of 1100 bp and 830 bp, respectively, were polymorphic between orange- and red-fruited bulks constructed from F-2 individuals in the L. esculentum and L. cheesmanii mating series. OPAR18(1100) and LrBC792(830) displayed recombination frequencies of 4.2% and 7.6%, respectively, in F-2 progeny. The B-linked OPAR18(1100) marker was also mapped to the long arm of chromosome 6, proximal to Mo-B, and revealed linkage between B and Mo-B.