Mr. Kidanemaryam Wagaw

Water deficit and salinity are the most abiotic constraints that affect viticulture sustainability. Grafting can improve a scion’s tolerance to stress, ultimately optimizing its productivity and quality. Identifying metabolic and physiologic responses of grafted grapevine to water deficit and salinity is crucial. We examined berry quality and composition from grafts of Syrah scion on Paulsen1103 and SO4 rootstocks under combinations of salinity (0.5 and 2.5 dS/m) and irrigation levels (66%, 100%, and 133%). The results showed that berry weight was less affected in graft SO4 as compared to graft Paulsen1103 across treatments. Spectrophotometer readings showed that saline deficit irrigation increased tannin content in berries and decreased carotenoid content. Similarly, berries from both rootstocks had an insignificant difference in nitrogen and hydrogen content, while carbon content decreased in Paulsen1103 under saline deficit irrigation. Chloride ions accumulated more in wine made from graft SO4 than Paulsen 1103,  indicating the difference between the two rootstocks in salt exclusion capacity. GC-MS-based primary metabolites from must and wine showed the interaction between salt, water regimes, and rootstocks altered the accumulation of major sugars and amino acids. Under salt stress, the relative content of metabolites, such as proline and alanine, were increased, while lysine, valine, and leucine declined,  compared to the control. In contrast to SO4, the wine and must from Paulsen1103 accumulated more amino acids (pyroglutamate, leucine, and valine), sugars (lyxose, xylose, and trehalose), and some other metabolites (ethanolamine, cinnamate, lactate, and galactarate). Altogether, water deficit and salinity induced the reduction in yield and quality by impacting berry weight and composition.