Date of Award

7-2021

Degree Name

MS in Agriculture - Crop Science

Department/Program

Horticulture and Crop Science

College

College of Agriculture, Food, and Environmental Sciences

Advisor

Jean Dodson Peterson

Advisor Department

Horticulture and Crop Science

Advisor College

College of Agriculture, Food, and Environmental Sciences

Abstract

A two-year study was conducted at a commercial vineyard in California’s Templeton Gap AVA to evaluate the effect of vine age on viticultural, enological, and sensory attributes of Vitis vinifera L. cv. Zinfandel grapes and wines. The experimental block was dry farmed, conventionally managed, with own-rooted Zinfandel vines that, when determined unproductive, were replaced with new vines of genetically identical scion plant material grafted onto St. George (Vitis rupestris Scheele) rootstock. Treatments included Young vines (5 to 12 years old), Control (representative proportion of young to old vines in the block), and Old vines (40 to 60 years old). Results indicated Young vines progressed more slowly during berry formation and more rapidly during berry ripening than Old vines. Due to variation in the timing of sugar accumulation, Old vines were harvested 21 days after Young vines in 2019, and 9 days after in 2020. Old vines produced, on average between both seasons, 3.7 kg more fruit per vine than Young vines. Old vines also produced, on average between both seasons, 22.8 more clusters per vine than Young vines (5.41 tons/acre and 2.64 tons/acre, respectively). The larger vine capacity observed was attributed to Old vines having more arm, spur and dormant bud positions per vine than Young vines, in addition to larger trunk circumference and diameter. Vine age also had an effect on vine vegetative growth, with Old vines producing shorter internodes (25.5% decrease) and smaller shoot diameters (29.3% decrease) compared to Young vines. Young vines had higher mid-day stomatal conductance and tended to have higher mid-day photosynthetic rates, although no differences in corresponding pre-dawn measurements were found. While root architecture was similar between age groups, Old vines displayed greater rooting depths. Young vine wines had lower pH and titratable acidity than Old vine wines. Old vine wines were defined by a wider array and intensity of aromatics, including raisin, orange peel, black fruit and spices relative to Young vine wines which were defined by wet topsoil and pomegranate aromas. These results suggest the potential for greater yield and improved wine quality when extending the longevity of Zinfandel vineyards.

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