Impact of supplemental light on bud fruitfulness, physiology and vine yield of containerized ‘Traminette’ (French-American hybrid) and ‘Concord’ (Vitis labrusca)

Introduction The goal of this study was to pre-condition grapevine transplants for enhanced reproductive development, in order to be able to produce a crop in the same season of planting. We hypothesized that young potted grape transplants can be pre-conditioned to enhance reproductive development using supplemental light in a controlled environment greenhouse. The pre-conditioned vines were then planted in a commercial vineyard and fruitfulness and components of yield (COY) were measured for two consecutive years. Methods One-year old bare root Concord ( Vitis labrusca , own-rooted) and Traminette ((Joannes Seyve 23.416 x ‘Gewurztraminer’, 101-14) transplants were grown in 37 L grow bags in a greenhouse under three light intensity levels (4 replicates per treatment) for 101 days. These light treatments were a control with no supplemental light with a cumulative daily light integral (DLI) of 887 ± 113 mol m -2 (NSL), a medium supplemental light intensity treatment with a cumulative DLI of 2895 ± 173 mol m -2 (MSL) and a high supplemental light intensity treatment with a cumulative DLI of 4928 ± 302 mol m -2 (HSL). Results & discussion Potential fruitfulness, evaluated through bud dissections, was significantly higher under HSL for Traminette in secondary and tertiary buds. Concord however showed extensive bud necrosis in all treatments. After transplanting into a commercial vineyard, total observed bud fruitfulness was significantly higher in MSL and HSL in Traminette compared to vines grown without supplemental light. Observed enhanced bud fruitfulness in Traminette did not translate into higher yields, suggesting a potential need for optimized management methods conditioned vines in commercial vineyards. The use of supplemental light in a controlled environment greenhouse did increase potential fruitfulness in containerized ‘Traminette’ and observed fruitfulness in subsequently planted vines in a commercial vineyard. However, increased observed fruitfulness did not lead to higher yields in the year of planting. Similarly, ‘Concord’ did respond to greenhouse conditions with bud necrosis and less fruitfulness across all treatments. Our study suggests that a potential technology to condition grapevines for fruiting under greenhouse conditions needs to be adjusted to specific cultivars.