Low temperature exposure of root system and inflorescence affected flowering and fruit set in 'Chardonnay' grapevines (<i>Vitis vinifera</i>)

Abstract

The mechanisms by which low temperature affects flowering and fruit set of grapevines are poorly understood, as is the specific response of the grapevine root system and inflorescence to low temperature effects that reduce fruit set. This study aimed to determine the responses of the root system and inflorescence of the grapevine 'Chardonnay' to low temperature (10 °C) during flowering, and considered the possible mechanisms of low temperature effects on those parts. Temperature treatments of 10 °C or 20 °C were imposed to potted 'Chardonnay' grapevines in a glasshouse for up to two weeks during the early stages of flowering. When the root system alone was exposed to 10 °C (with the rest of the plant at 20 °C) during flowering, the number of attached berries and percentage fruit set were significantly reduced by 50 % than when the root system alone was exposed to 20 °C. Whereas, exposure of the inflorescence alone to 10 °C (with the rest of the plant at 20 °C) delayed flowering, allowed rachis to grow longer, and increased both the number of attached berries (from 22 to 62 per vine) and fruit set (from 8 % to 20 %), than when the inflorescence alone was exposed to 20 °C. This study will enhance our understanding of the possible mechanisms of low temperature effects on grapevine fruit set and productivity.