Associations among fruit firmness, morphological traits and RAPD markers in the "firm" tomato mutant

The Santa Clara Cultivar is widely known in the tomato-producing region of Viçosa (MG). Recently, tomato plants from the same cultivar with changes in morphological traits and post-harvest fruit characteristics have been identified. The inheritance study and the allelism test carried out by Schuelter et al. (2002) determined that a recessive gene with pleiotropic effects modified the expression of morphological traits, such as the color of stigma and fruits and the early leaf senescence. This gene, present in the ‘firm’ mutant (frm), was mapped on the tomato chromosome 10 region - the same region of the lutescent-2 (l-2) gene. However, the identification and location of the genes that increase the firmness of ‘firm’ mutant fruits remain unknown. Therefore, the objective of this study was to analyze the inheritance of morphological and firmness characteristics of fruits which were modified by the mutation using RAPD markers. Results demonstrated that the genomic region comprising the l-2 gene increases the fruit firmness, explaining from 6.27 to 25.09% the phenotypic variation for this trait along the 15 day-period of storage. However, the AQ16747 and AS8622 markers, mapped at 11.67 and 21.67 cM from the mutation frm, indicated that the further they were located from this region, the smaller proportion of the phenotypic variation they had. Thus, we can conclude that that the genomic region flanking the l-2 gene also increases fruit firmness in the ‘firm’ mutant, a trait that has never been associated with this gene.