Is it Possible to Combine High Content in Phenolics with Low Browning in Fruits and Vegetables? A case in Eggplant

Abstract

Demand among consumers for fruits and vegetables with improved contents in bioactive compounds is increasing. In particular, a lot of attention is being paid to phenolic compounds, as they have been reported to present many beneficial effects for human health. However, oxidation of phenolic compounds present in the tissues of fruits and vegetables by polyphenol oxidases (PPOs) can result in browning, which affects negatively the quality of the produce. Eggplant (Solanum melongena) presents a high content in phenolics, in particular chlorogenic acid (CGA), which confers nutraceutical properties to this crop. In order to obtain information relevant for the development of varieties with high content in CGA and low browning, we have studied the diversity for CGA, PPO activity, and fruit flesh browning and their relationships in a collection of 18 Spanish accessions of eggplant. Also, using an interspecific mapping population between S. melongena and S. incanum we have mapped the genes involved in the synthesis pathway of CGA as well as the eggplant PPO genes. The results confirmed that eggplant presents high levels of CGA, and that a wide diversity exists for the three traits studied. Low levels of correlation have been found between CGA and PPO activity on one side and browning on the other, indicate that PPO is not a limiting factor in browning in the germplasm collection studied. The six genes of the pathway for the synthesis of CGA from phenylalanine have been mapped to five different linkage groups. Only two of the genes are linked indicating that selection of materials with the alleles favourable of different parents will be easily achieved. However, the five PPO genes mapped (PPO1 to PPO5) cluster together in the same linkage group, which will difficult obtaining recombinants. Mapping of these genes is of interest for marker assisted selection for high content in CGA and reduced browning. Overall, the results indicate that selection of eggplant varieties with high content in CGA and low browning is feasible. The information obtained is also useful for the genetic improvement of other fruits and vegetables in order to develop new cultivars with increased added value resulting from high content in phenolics and low browning.