Anthocyanins Reduce Fungal Growth in Fruits

Abstract

As the most visible role of anthocyanins is to impart colors, the adaptive significance of anthocyanins in plant reproductive organs is invariably attributed to the attraction of seed dispersers and pollinators. However, few studies suggested that anthocyanins in vegetative tissue might also function in plant defence, although the evidence for such a function is not particularly strong. Here, we investigated whether anthocyanins contribute to fruit defence against fruit-rot fungi. We found that the risk of fruit-rot in grape varieties infected with Botrytis cinerea decreased with increasing anthocyanin contents. Moreover, anthocyanin contents directly inhibited growth rates of nine fruit-rot fungi on agar plates. Anthocyanins reduced fungal growth by 50% in the concentrations that typically characterise unripe blackberries and by 95% in the concentrations that typify ripe blackberries. We conclude that anthocyanins in fruits not only function to attract animal vectors, but that they also contribute to fruit defence. The antifungal activity of anthocyanins might more widely explain their occurrence in various plant organs such as vegetative tissue and roots.