As water availability decreases and human demand for water increases, it is necessary to minimize vineyard water use while maintaining wine quality and yield. To assess rootstock and irrigation effects in tandem, a vineyard was established in 2008 in Mt. Vernon, Missouri. Six irrigation zones were installed, allowing randomization of blocks for three different irrigation regimes and four different rootstocks. Chambourcin vines, either own-rooted or grafted onto 1103P, SO4, or 3309C, were planted and either (i) nonirrigated, (ii) irrigated at full replacement of evapotranspiration (ET), or (iii) irrigated at 50% of the potential ET (RDI). From 2013 to 2015, soil moisture, leaf gas exchange, leaf chlorophyll content, canopy density, yield metrics, and vegetative growth were monitored and harvested fruit was vinified. In the unirrigated and RDI treatments, the drought decreased mean volumetric soil water content. Midday leaf water potential indicated varying tolerance of water stress, with own-rooted vines showing greater stress under all three irrigation regimes than vines grafted onto SO4 rootstock. Photosynthetic carbon assimilation rate was reduced in nonirrigated and RDI vines on all rootstocks. There were positive correlations between midday mean volumetric soil water content and leaf water potential, leaf stomatal conductance, and leaf transpiration rate. Nonirrigated vines had significantly altered canopy development, a reduced percentage of interior clusters, and increased cluster flux availability and flux symmetry. Treatments influenced fruit composition at harvest with differences in berry weight: in vines grafted onto SO4, full irrigation produced larger berries than both other grafted and own-rooted vines. Differences in fruit composition included higher juice soluble solid content in fruit from own-rooted, nonirrigated vines than in fruit from SO4-grafted, fully irrigated vines. Also, higher juice pH was measured in fruit from 1103P-grafted, partially irrigated vines than in fruit from own-rooted vines.

Funding Support: Missouri Wine and Grape Board