How temperature stress changes carrot flavor: Elucidating the genetic determinants of undesired taste in carrots

Global climate change and warming temperatures represent the greatest future challenge for global food production and quality. In this project, we will define the genetic factors of climate-associated taste deficiencies in carrot. Carrot is considered one of the leading horticultural crops in the world in terms of its nutritional value, health benefits, and unique flavor based on its high content of carotenoids and volatile aroma compounds. In recent years, carrot genotypes of different color with improved nutraceutical attributes have been developed. When exposed to high growth temperatures, carrots develop an undesired harsh and bitter taste caused by the accumulation of terpene metabolites. This taste deficiency represents a quality defect to carrot breeders and large- scale growers and needs to be minimized for successful marketing of carrot crops. Surprisingly, the genetic determinants of bitter and harsh flavor in carrot and their response to temperature stress are not well characterized. We started to elucidate these factors in different carrot cultivars by investigating the biosynthesis of volatile terpenes, which represent the predominant flavor compounds in carrots. Also, up to date we identified and characterized two terpenesynthase enzymes, one of which produces (E)-β- caryophyllene, a major terpene component in carrot root. Both TPSs may contribute to the observed variation in volatile terpene formation.