Mathematic model for simulating anthocyanin composition during grape ripening: another way of phenotyping

Anthocyanins are responsible for grape color, an important quality factor for market acceptance. The relative proportion of cyanidin-based (cyanidin-and peonidin-derivatives) and delphinidin-based (delphinidin-, malvidin- and petunidin-derivatives) anthocyanins largely determines the color variation among red/purple/blue colored grape varieties. Anthocyanin biosynthesis is under complex regulation by nutrients, hormones, and environmental cues sensed by the berry. However, the physiological mechanisms underlying these regulations are poorly understood. A dynamic model was developed to simulate the developmental anthocyanin composition in two genotypes and different carbon and nitrogen conditions. This model describes the flux partitioning by basic chemical reaction rules with total anthocyanin as input and reaction rates as parameters. Data were gathered from two experiments, which studied the developmental changes in anthocyanin composition. The model was calibrated for two cultivars under a given growth condition and then validated by applying the model to other conditions for the same cultivar. The model can successfully simulate all the observed modifications in anthocyanin composition throughout berry ripening. This provides an alternative way of phenotyping by dissecting a complicated trait (anthocyanin content and composition) into developmentally stable traits (model parameters).