Hormonal Control of Grape Berry Ripening

The first steps of berry development, from fertilization to nouaison (fruit set) are under the control of developmental hormones such as auxins, cytokinins and gibberellins that promote cell division and cell expansion. These hormones reach a maximum concentration just before véraison and then decrease sharply upon ripening. Ultimately, the final size of the berry depends on how many seeds it contains.

The three hormones responsible for the grape berry maturation post-véraison include:

• Abscissic acid:
• shows a considerably accumulation after véraison
• a delay in ABA accumulation correlated with a delay in the import of hexoses and may play a role in sugar accumulation
• may also positively influence the accumulation of phenolics in the grape
• plays a role in seed maturation and seed dormancy
• resistance to water stress deficit
• specifically involved in seed maturation control
• Ethylene
• present at low but steady levels along berry development and ripening
• may have in regulating the vascular fluxes associated with berry ripening
• implicated in the reduction of berry acidity during the ripening phase
• exogenous ethylene treatment at véraison was shown to enhance the accumulation of anthocyanins in grape berries
• can have an effect on development of grape flavour and aroma
• Brassinosteroids
• concentration in the grape increases at the onset of ripening
• exogenous treatment of these hormones has hastened berry ripening

References:
1. Text and illustration from: Carlos Conde, Paulo Silva, Natacha Fontes, Alberto C. P. Dias, Rui M. Tavares, Maria J. Sousa, Alice Agasse, Serge Delrot, Hernâni Gerós, Biochemical changes throughout Grape Berry development and fruit and wine quality, Food, 1(1), 1-22 ©2007 Global Science Books.