Interaction of rootstock and applied water amounts at various fractions of estimated evapotranspiration (ETc) on productivity of Cabernet Sauvignon

Background and Aims: It is commonly thought that grapevine rootstocks vary in their tolerance to drought. This study examined the interaction between various applied water amounts and productivity of Cabernet Sauvignon grafted onto five rootstocks. Methods and Results: The commercial vineyard used in this study was located along the central coast of California. The rootstocks used were Teleki 5C, 110 Ricter, 140 Ruggeri, 1103 Paulson and Freedom. Irrigation amounts ranged from 0.25 up to 1.25 of estimated vineyard evapotranspiration. Midday leaf water potential (Ψ_l), was significantly affected by irrigation treatment but not by rootstock. There was a significant effect of irrigation treatment and rootstock on berry weight, number of bunches per vine and yield but no interaction between those two factors. The rootstock 5C had the lowest yield compared with the other rootstocks. Yield at the 0.25 irrigation level was approximately 62% of the yield at the 1.25 irrigation level across rootstocks. Irrigation treatment was the only factor that significantly affected soluble solids in the fruit. There was a significant interaction between rootstock and irrigation amount on pruning weights. Berry weight, yield and pruning weights were linearly correlated with midday Ψ_l across rootstock and year. Conclusions: The results indicate that the rootstocks producing greater yields at the highest applied water amounts also produced greater yields when deficit irrigated. Significance of the Study: Under both stressed and non-stressed conditions, the rootstocks with the highest yield were those with the greatest number of bunches.