Evaluation of nutrient uptake on grapevine resistant cultivars

The search for valid alternatives to cultivated varieties of Vitis vinifera has recently identified new resistant and/or tolerant genotypes to the main cryptogams (downy and powdery mildew), to be used in enhancing sustainable viticulture. These cultivars represent the result of interspecific crossings, obtained from some important European research centers in viticulture, using Vitis vinifera cultivars and other Vitis species of American and Asian origin. In two sites of northeastern Italy characterized by different soil pH levels, during the period 2015-2019, 15 resistant cultivars – ‘Aromera’, ‘Baron’, ‘Bronner’, ‘Cabernet Cantor’, ‘Cabernet Cortis’, ‘Cabernet Carbon’, ‘Cabino’, ‘Helios’, ‘Johanniter’, ‘Monarch’, ‘Muscaris’, ‘Prior’, ‘Regent’, ‘Solaris’, and ‘Souvignier gris’ – were monitored in order to have information about agronomical and nutritional behaviour. Yearly, 15 plants for each cultivar/site were evaluated at fruit set, with regard to nutritional aspects through leaf analyses and leaf green colour (SPAD indexes), as well as for photosynthetically active biomass behaviour (normalized difference vegetation index – NDVI indexes) at pre-veraison. Weather conditions of different years strongly changed the absorption and availability of nutrients in plants and their behaviour for both indexes. ‘Regent’ and ‘Johanniter’ showed the highest nitrogen (N) uptake, while ‘Solaris’, ‘Muscaris’, and ‘Monarch’ had the lowest leaf contents. ‘Baron’ and ‘Cabernet Carbon’ showed the highest levels of vigor associated with greener leaves, while ‘Cabernet Cortis’ and ‘Prior’ had the lowest values of NDVI and SPAD. ‘Cabernet Cortis’ and ‘Solaris’ revealed potassium (K) deficiencies, while ‘Bronner’ and ‘Souvignier gris’ enhanced the availability of this cation, strongly depressing magnesium (Mg). ‘Johanniter’, ‘Regent’, and ‘Monarch’ had low Mg uptake too. ‘Monarch’, ‘Aromera’, and ‘Bronner’ showed low zinc (Zn) nutritional status in the leaves. Collected results allows us to suggest interventions aimed at a more suitable nutritional management for resistant cultivars, in confront of Vitis vinifera, above all for N, K, and Zn; in particular for Mg, early foliar treatments should be recommended, especially in years where rainfall is concentrated in the spring month