Complementation of the Tomato anthocyanin without (aw) Mutant Using the Dihydroflavonol 4-Reductase Gene.

We isolated the dihydroflavonol 4-reductase (DFR) gene from tomato (Lycopersicon esculentum) using a previously characterized cDNA as probe. Earlier studies had indicated that the DFR gene is present in tomato as a single gene located on chromosome 2 near the locus anthocyanin without (aw). Mutant alleles of the aw locus result in the complete absence of anthocyanin pigmentation throughout all stages of plant development. When the genomic DFR clone was introduced by Agrobacterium-mediated transformation into plants bearing the aw mutation, primary transgenic seedlings accumulated anthocyanins that could be observed while the plants were still in tissue culture and which continued to be observed as the plants matured. Progeny of self pollinated and backcrossed transgenic plants segregated for anthocyanin pigmentation, and Southern hybridization analyses indicated the presence of the DFR transgene exclusively in those plants with pigmentation. These data indicate that the aw locus likely corresponds to the structural gene for DFR and that DFR can be used as a visual, nondestructive, plant-derived marker gene for tomato.