Delayed root water supply result in spring dieback of Cabernet Sauvignon in northern China

Cabernet Sauvignon (Vitis vinifera) is one of the main wine-making varieties in the world. Its budding time is late, and cane dieback often occurs in northern China. In order to analyze the causes of shoot drying death of Cabernet Sauvignon in spring, the water supply capacity of the roots of Cabernet Sauvignon and Early-ripening Kyoho and the dynamic changes in the respiration metabolism of roots and buds during the ecodormancy were studied. Additionally, the effects of rootstock SA15 grafting on the sap flow and moisture content changes of Cabernet Sauvignon canes were investigated and the expression of root respiration related genes at different temperatures during the ecodormancy after rootstock SA15 grafting was analyzed. The results showed that compared with Early-ripening Kyoho, the xylem sap flow intensity of Cabernet Sauvignon was low and unstable during the ecodormancy, the roots water reached the peak later, and changes in the respiratory pathways and the accumulation of soluble sugar occurred slowly. The peak of the activity of the respiratory pathways in the Cabernet Sauvignon buds occurred significantly earlier than that of the roots. Compared with self-rooted vines, the peak in the sap flow of Cabernet Sauvignon canes grafted on rootstock SA15 occurred 24 days earlier, and the recovery times of the total water content and free water content occurred earlier. It also increased the roots respiration intensity and the expression of key enzymes of roost respiration under low temperature. In summary, Cabernet Sauvignon insufficient water supply capacity, resulting in difficulty replenishing the water lost from the canes in time and ultimately leading to spring dieback of Cabernet Sauvignon canes. The moisture recovery time of Cabernet Sauvignon canes can be increased by grafting them on rootstock SA15 to prevent the occurrence of spring dieback.