Thayne Montague,* Edward Hellman, Pierre Helwi, and Emily Graff
*Texas Tech University / TAMU AgriLife Research, Texas Tech University, Department of Plant and Soil Science, Lubbock, TX, 79409-2122 (thayne.montague@ttu.edu)

In 2017, the grape and wine industry had an overall economic impact of $13.1 billion within the state of Texas. However, most Texas vineyards are subject to late spring frosts, which potentially reduce crop yields and fruit quality. If Texas grapegrowers were knowledgeable regarding cultivar secondary bud fruitfulness, secondary bud fruitfulness might influence variety selection during vineyard planning. Therefore, objectives of this experiment were to analyze data from a two-year study comparing growth and fruitfulness of shoots grown from primary and secondary buds of Vitis vinifera Grenache grafted to three rootstocks (110R, 1103P, and Freedom) on the Texas High Plains. Grenache vines (vertical shoot-positioned trellis, bi-lateral cordons, four spurs/cordon, and two buds/spur) were planted in a randomized complete block design in 2006. Treatments were repeated on the same vines over consecutive growing seasons (2016 to 2017) and included: primary bud remained, and following budbreak allowing shoot growth to reach 15 cm in length, then removing primary buds. Pruning weight, gas exchange, and fruiting data were collected each year. During the first growing season, gas exchange data from leaves grown on secondary bud shoots tended to have greater gas exchange rates. Second year gas exchange data indicate no differences. Pruning weights suggest greater vegetative growth of shoots grown from primary buds or on rootstock 1103P. In general, each year fruit grown on primary bud shoots had greater berry weight, cluster weight, and yield than fruit grown on secondary bud shoots (across rootstocks, yield was reduced nearly 98% in year one, and 33% in year two). Berry brix levels were also influence by rootstock and bud removal. Results of this study offer new insight into the response of Grenache vines to potential early frost damage.

Funding Support: Texas AgriLife Research and Extension, State of Texas Viticulture and Enology Research, Education, and Engagement Funding