Vine growth and physiological performance of two red grape cultivars under natural and reduced UV solar radiation

Background and Aims: Under natural conditions the grapevine has shown different growth and physiological responses to high UV radiation. We evaluate the effect of natural and reduced UV-B, UV-A and photosynthetically active radiation (PAR) on vine growth, physiological status and berry composition in Bovale Grande (syn. Carignan) and Cannonau (syn. Grenache) field-grown grapes. Methods and Results: During the two seasons of the trial, UV-screening treatments Visible+UV-A and Visible, imposed with plastic tunnels from pea size onward, promoted a significant difference in UV and PAR transmission as compared with that of plants exposed to natural sunlight, but did not reduce canopy growth and yield. Plants adjusted leaf gas exchange and water status to both high and reduced UV and PAR radiation. The concentration of phenolic substances of berries was significantly higher under natural UV, whereas accumulation of anthocyanins responded differently in the two cultivars according to the duration of high temperature. Conclusions: The results indicate that red grapes of Mediterranean origin are able to adapt growth and physiological responses to high natural UV and temperature, but accumulation of berry anthocyanins and phenolic substances can vary considerably according to sensitivity of cultivars to these abiotic factors. Significance of the Study: Increasing knowledge on the acclimation responses to high UV and solar irradiance environments by grape cultivars may help to improve management practices towards greater adaption to global warming conditions and projected climate change.