RAPD and AFLP tagging and mapping of Beta (B) and Beta modifier (Mo-B), two genes which influence beta-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 whic h segregates independently of B. RAPD and AFLP analyses were performed usin g near isogenic lines : for B and bulked segregant analysis (NILs) unique ( BSA) of a L. esculentumXL. cheesmanii-derived F-2 population segregating fo r B. Using 1018 random primers for RAPD analysis and 64 primer pairs for AF LP analysis, we identified polymorphic products which distinguished the NIL s 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 coseg regated 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 map ped to the long arm of chromosome 6. Two RAPD products (OPAR18(1100) and UB C792(830)) of 1100 bp and 830 bp, respectively, were polymorphic between or ange- and red-fruited bulks constructed from F-2 individuals in the L. escu lentum and L. cheesmanii mating series. OPAR18(1100) and LrBC792(830) displ ayed recombination frequencies of 4.2% and 7.6%, respectively, in F-2 proge ny. The B-linked OPAR18(1100) marker was also mapped to the long arm of chr omosome 6, proximal to Mo-B, and revealed linkage between B and Mo-B.