Coloração e conservação pós-colheita de frutos em híbridos de tomate em função dos alelos norA, ogc e rin

Abstract

Multiple genes may affect fruit color in tomatoes. Although major genes have individual effects, it is often the interaction between these major genes that produces the fruit color phenotype. Fruit color is a combination of pigments present in of three different types of tissues; epidermis, pericarp, placenta, and columella. We evaluated yield and quality of tomato hibrids and compared the effects of the mutant alleles alcobaça (norA), ripening inhibitor (rin) and old gold crimson (ogc), in heterozygous and / or homozygous conditions, in the expression of color and conservation of postharvest quality of fruit in tomato genotypes. Twelve experimental hybrids obtained by crosses which included three lines bearing the alleles alcobaça, ripening inhibitor and old gold crimson (TOM-591 – norA/norA ogc/ogc; TOM-761 – ogc/ogc rin/rin), a line carrying the rin allele (TOM-667 – rin/rin) and six normal strains. A randomized complete block design was deployed, with 14 treatments (12 experimental hybrids and 2 controls - the hybrid Giselle - normal and Colono - rin+/rin) and 4 replications. Both external and internal fruit color were assessed with a Minolta CR-400 colorimeter in the CIE L*, a* and b* mode. Hue and chroma readings were taken of four different points of the fruit (epidermis, pericarp, placenta, and columella). The fruit quality-related traits included shelf life (firmness in the breaker stage) and the content of soluble solids was evaluated. Yield related traits: total yield, early yield, average fruit mass, fruit shape and locule numbers. There also evaluated yield traits were not influenced by genotypic constitutions in loci rin, norA and ogc; there were however, genotypic background, mainly in the average fruit mass. Genotypes rin+/rin and nor+/norA contributed by conditioning greater firmness of tomato fruit at harvest point (breaker stage). The genotypes rin+/rin presented the worst internal fruit colors. There was a positive effect of ogc+/ogc in improving internal color rin+/rin and nor+/norA fruit making, it similar to that of normal genotypes. The triple combination ogc/ogc rin+/rin nor+/norA was considered the most promising to maintain or improve internal color (placenta) of the fruit, at the same time improving the postharvest conservation of tomato fruit.