Preliminary evaluation of agronomic and enological properties of preselected grapevine clones of ‘Tempranillo’ and ‘Graciano’ in DOCa Rioja (Spain)

Abstract

AIM. Cultivation of a few number of clones is causing the loss of vineyard biodiversity, resulting in the disappearance of biotypes that could be of interest to face future challenges, such as climate change or appearance of new pests. This topic is so relevant that OIV dedicated a recent resolution (OIV, 2019) to the recovery and conservation of intra-varietal diversity. In order to avoid the loss of grapevine intra-varietal diversity of DOCa Rioja grape varieties, Regional Government of La Rioja established a germplasm bank with more than 1.600 accessions, which origin lies in the prospecting and sampling of ancient vineyards located throughout the whole region. 30 clones of Tempranillo and 13 clones of Graciano were preselected and multiplied in a new vineyard for further observations. The aim of this work is to describe the first results obtained from the agronomic characterization of these preselected clones, which constitute the base of a new clonal selection that aims to increase the range of available certified clones.

METHODS. Candidate clones (30 cv. Tempranillo; 13 cv. Graciano) were planted in 2016 in an experimental vineyard in La Rioja (Spain). A complete randomized block design was set up with four replicates of 10 plants. In 2020, clones were evaluated according to their phenological data (time of bud burst, full bloom, veraison and physiological ripeness). At harvest, yield parameters were determined: weight of 100 berries (g), cluster weight (g), fertility (clusters/shoot), yield (kg/plant) and cluster compactness (OIV descriptor Nº204). Must chemical composition was determined by analyzing ºBrix, pH, total acidity (g/l), tartaric acid (g/l), malic acid (g/l) and potassium (mg/l). The following vegetative growth parameters were determined: average shoot weight (g), pruning fresh weight (kg/plant) and Ravaz Index. In addition, clones were vinified and wine physical-chemical parameters, total phenolic index (TPI), anthocyanin content (mg/l) and color intensity were determined.

RESULTS. Significant differences between clones were found for each parameter. Results confirmed therefore the huge wide genetic variability existing between the clones regarding their agronomic behaviour. Moreover, clones also showed great differences regarding wine composition. Nonetheless, data collection needs to continue for at least 3 vintages in order to fulfill their caracterization independently from climatic conditions.

CONCLUSIONS

Clones have shown big differences in many of the parameters analyzed. The diversity found is a potential tool for the selection of those candidates with the best properties and constitutes the best guarantee of adaptation of these varieties to future objectives and environmental conditions.