DEVELOPING SUSTAINABLE GRAPEVINE NURSERIES. THE OPTIMIZATION OF IRRIGATION AND NITROGEN INPUTS TO ENHANCE CARBON RESERVES

This work is the output of an industrial PhD in collaboration with Vivai Cooperativi Rauscedo (VCR), one of the few nurseries specialized in the production of grafted vine plants. During the nursery propagation process, plants are subjected to stresses that might jeopardize their transplanting performance and, in some cases, their survival. As a result, each step of the production process is characterized by plant losses that cannot be optimized by the canonical methods of plant evaluation, often focused on sanitary aspects. Studies on NSC dynamics in woody crops are reported in the literature, often using grapevines as model plants. However, the nursery production process is poorly investigated, although plants are more fragile and require more attention. The project was based on identifying the mechanisms that could facilitate grafted grapevines to increase carbon reserves. We hypothesize that controlled water and nutritional deficits, plant hydraulic strategies, and cultivar/rootstock combination could shape the NSC concentrations in different organs. Therefore, the first aim was to decipher the responses of different cultivar/rootstock combinations of one-year-old grapevines subjected to water and nitrogen deficit. Subsequently, the acquired knowledge was transferred to the nursery. Our results confirmed that NSC concentration constitutively depends on cultivar and rootstock genotype and is mainly modulated by seasonal dynamics. As expected, at the cane maturity stage, NSC concentration is higher. Among the organs investigated, roots appear as the key organ accumulating carbon reserves and the one that respond to water and nitrogen availability. Specifically, a reduction of water supply could favour the accumulation of NSC in the roots, while nitrogen regimes provide conflicting responses. Furthermore, we realized that the mechanisms of NSC accumulation could be better understood by dividing the different pools into sugars, starch degradation products, and starch. The latter may be a proxy for the total NSC. This thesis focused on specific stages of the plant production process in the nursery. Future studies should integrate and apply the knowledge gained to the cutting conservation stage, which could affect the respiration rate and, hence, the NSC content. Consequently, this dissertation concludes with a recommended exploratory study on oxygen consumption in grapevine cuttings at 4 and 9°C, that offers a proof-of-concept beneficial for future investigations. In conclusion, we believe that evaluating carbon reserves can be very useful in directing management toward greater sustainability and a future assessment of the quality of grafted grapevines.