Elucidating the mechanisms controlling the carotenoid retention trait in Capsicum annuum.

Fruit colour is a key quality trait in chilli pepper (Capsicum annuum), and carotenoids are the major pigments responsible for conferring the red colour observed in pepper fruits. Carotenoids have valuable antioxidant properties. Post-harvest storage of peppers is often required in order for consumer demand to be met, and therefore peppers must retain their quality during storage. An understanding of changes in carotenoid content is essential for high quality carotenoid retaining lines to be bred.
In the present study, the mechanisms underlying the carotenoid retention trait have been investigated. Biochemical profiling, employing both HPLC-PDA and GC-MS has revealed changes in carotenoid content in the fruit of a Doubled Haploid population (375 associated lines), and has revealed that the carotenoid retention trait and intermediary metabolism are not linked. Physiological analysis of fruits has revealed the role of the fruit cuticle in controlling the carotenoid retention phenotype. The fruit cuticle protects fruit from carotenoid degradation by acting as a barrier to harmful oxidative species, which can result in non-enzymatic carotenoid cleavage. Transcriptomic analyses have resulted in the identification of candidate genes underlying the carotenoid retention trait, and a method of Virus Induced Gene Silencing (VIGS) has been established in pepper fruit for functional characterisation of genes, and validated in tomato.
This study sheds light on a previously understudied trait. Understanding the mechanisms underlying carotenoid retention in chilli pepper will not only result in breeding of improved pepper varieties, but this information may also be translated to other crops, which also experience costly post-harvest carotenoid degradation, and consequently, reduced antioxidant properties and nutritional content.