Effect of grafting on xilem efficiency/safety modulation and photosynthetic performance in Vitis vinifera “piedirosso”: concerns in a climate change scenario

Vitis vinifera L. is the most widely cultivated and economically important fruit crop in the world (1). Italy, one of the world’s leading wine-producing countries, shows vineyards distributed all over the mainland. In this scenario, Campania region, due to its peculiar climatic conditions and fertile soils, has always been considered one of the most appreciated districts for wine production (2). Additionally, the presence of several autochthonous grape varieties is a mainstay for this region. Italian legislation does not allow the irrigation of vineyards in order to preserve wine quality in most quality assurance labels. However, the ongoing climate changes are determining constraints in viticulture due to rising temperatures, changes in precipitation frequency and occurrence of extreme events, such as heat waves. Grapevine (Vitis vinifera L.) yield is expected to suffer from climate change also given that fruit development and ripening occur in the hottest and driest season (3) (4). In the last years, in the sight of climate change, the attention has been rise non wine production sustainability, particularly considering the possibility to adopt cultivation techniques aimed to enhance physiological adaptation to drought (5). In some volcanic areas of the Campania Region, grapevine cultivation is traditionally performed by avoiding the use of rootstocks thanks to the soil type that is inhospitable to Phylloxera pest. In this context, the aim of the study is to assess how the use of grafting on rootstocks could influence plant adaptation to drought and grape production. This study was conducted on Vitis vinifera L. ‘Piedirosso’ grapevine which is an autochthonous cultivar of the Campania Region. Plant growth, yield, photosynthetic performance and anatomy of water stem-leaf pathway were analysed in plants grown on their own-roots or grafted onto 420A rootstock (Vitis riparia x Vitis berlandieri). The selected vineyard Vigna Jossa was located within the farm Cantine degli Astroni, in the Campi Flegrei area at 200m above sea level (Naples, Southern Italy). Grafted and non-grafted plants were compared on the basis of several morphological and eco-physiological parameters including: plant architecture, leaf and wood stem anatomical traits, photosynthetic efficiency (by determination of quantum yield of PSII electron transport, maximal photochemical efficiency and pigment content), gas exchanges, etc. The overall results showed that the expected differences in growth performance and productivity in the two types of plants, were consequent to different eco-physiological and structural properties suggesting a different capability to modulate gas-exchanges and water flow efficiency/safety against embolism under different conditions of water availability. Hence, this study suggested the occurrence of higher plasticity of plant traits involved in the regulation of water flow in the grafted system. Such findings induce to better evaluate the opportunity to move from a traditional cultivation with own-rooted grapevines towards grafted models in the sight of increasing drought. As an alternative, the maintenance of the traditional own-rooted cultivation system should be accompanied by further cultivation trials aimed to optimize training system and plant management.