Which statement best defines coulure in grape development?

• A. A condition of the grape bunch in which fruit set has failed for a high proportion of flowers due to unsuccessful ovule fertilisation.
• B. A condition of seedless grapes.
• C. A weather phenomenon causing irregular berry size.
• D. A disease affecting vines.

Answer: (C)

Coulure describes a problem of fruit set at bloom, where many flowers fail to develop into berries because fertilization of the ovules does not occur. This means that even though flowering happens, the flowers don’t progress to fruit, leading to poor or uneven set in the cluster. Weather during flowering can influence it—cool, wet conditions can hinder pollen viability and pollen tube growth—but the term itself refers to the outcome (failure of fertilization and fruit set), not a weather event or a disease. It’s not about seedless grapes, a weather phenomenon, or a vine disease.