Influence of Grapevine Rootstock on Scion Development and Initiation of Senescence

Goals: The purpose of this research was to determine if scion development and the timing of phenologic events could be affected by rootstock selection. Deciphering the influence of rootstock on scion traits such as shoot internode length and diameter, yield, pruning weight, light penetration (photon flux density, PFD) into the cluster zone, initiation of leaf senescence, and progression to vine dormancy would enable growers to better address climatic changes and associated stressors.

Key Findings:

• Vines grafted onto 110R (Vitis berlandieri × V. rupestris) had lower light (PFD) penetration in the cluster zone, more clusters, and greater pruning and crop weight per vine compared to scions grafted onto 101-14Mgt (V. riparia × V. rupestris).

• Scion cultivars grafted onto 110R had greater shoot internode length and diameter than those grafted to 101-14Mgt.

• Vines grafted to 101-14Mgt initiated leaf senescence and reached dormancy earlier than those grafted to 110R, and dry farming resulted in faster senescence of Cabernet Sauvignon scions grafted to 101-14Mgt.

Impact and Significance: Rootstock choice plays a key role in scion development and can be used to induce earlier dormancy to address late-season precipitation risks during harvest or to conserve soil water resources in areas prone to drought conditions. Rootstock choice can also play a role in extending leaf function, delaying dormancy, and allowing berries additional time to attain better ripeness. A leaf senescence index could be used to classify existing rootstocks and to help in screening new germplasm and rootstock selection. Rootstock selection can also be used to manipulate pruning and cluster weights, canopy density, and light penetration into the fruiting zone. Understanding the response of scions to rootstock selection is of practical and economic importance in winegrape production.