Controle genético do teor de sólidos solúveis e do sabor em tomate

Abstract

The objectives of this study were to determine the inheritance, the gene action and to estimate the number of genes involved in the genetic control of soluble solids content and taste in tomato fruits. Initially, 53 tomato accessions belonging to the following varietal groups were evaluated: Grape, Salad, Saladete and Industry, as well as seven species of wild tomato (Solanum pennellii, Solanum chilense (2), Solanum hirsutum, Solanaceae, Solanum huaylasense, Solanum seaforthianum). The experiment was established in a greenhouse and designed with a completely randomized block design with three replicates, using two plants per replicate. At the physiological maturation stage, the fruits were evaluated for soluble solids content (SS) and titratable acidity (TA). Based in these indexes, we determined the SS/TA ratio that characterized the flavor fruit. The data were submitted to analysis of variance and the means of the genotypes grouped by the Scott & Knott cluster analysis at 5% of probability. In addition, the genetic parameters were estimated through the mathematical expectation of the mean squares of the analysis of variance. The genetic variability for the tomato fruit quality was obtained by the analysis of genetic dissimilarity between the accessions, estimated by the phenotypic data of soluble solids and the molecular polymorphism obtained by AFLP marker. The genetic inheritance of organoleptic characteristics was determined from the analysis of generations means. Two families obtained by Grape x Salada (family 1) and Grape x Rin (family 2) crosses were evaluated. The experiment was established in a randomized block design with three replicates. The treatments were arranged in split plot design. The family effect was studied in the main plots while the segregation generations were evaluated in the subplots. Each family was composed of six generations (P1, P2, F1, F2, RC1 and RC2), from which we determined the soluble solids content, titratable acidity and average fruit weight by statistical and genetic analyzes. The results showed a phenotypic contrast between the tomato accesses, especially Grape, which presented high SS content and flavor. On the other hand, the accesses of type Salada and Rin were those that obtained the worse performance for these characteristics. The estimated genetic parameters indicated low participation of the environmental effects in the expression of the flavor character evidencing the possibility of genetic gains with the artificial selection. The results show the predominance of additive effects for the soluble solids and flavor in the two families analyzed with polygenic genetic control. Estimates of heterosis were high and positive for the characteristic flavor in the Grape x Salada family, evidencing the potential to obtain individuals higher than the average of the parents. Heritability in the restricted sense was up to 17.5 for SS and 77.7% for flavor, confirming the facility of artificial selection for the flavor in tomato breeding programs. The predominance of additive gene action, associated with high heritability and heterosis for the flavor, allows us to infer the effectiveness of the genetic gain during artificial selection. However, for the soluble solids, the low heritability associated to the high number of genes indicates a lower efficiency and a difficulty of the artificial selection for this characteristic.