Runze Yu, Luca Brillante, Johann Martinez-Luscher, and Kaan Kurtural*
*University of California Davis, 1 Shields Avenue, Davis, CA 95616 (skkurtural@ucdavis.edu)

A Crimson Seedless vineyard was modeled to examine the ecophysical variation and plant water status influence on productivity and berry chemistry over two years. Electrical conductivity (EC) of the soil was proximally sensed with electromagnetic induction. A stratified random sampling method and an equidistant 30 × 30 m grid sampling were used in 2016 and 2017 to ground-truth proximally sensed data. Deep EC was related to variation of plant water status in 2016 (R2 = 0.4897); however, shallow EC did not explain the variation in water status. Grape primary metabolism was measured for total soluble solids, total acidity, pH and berry weight. Only pH in 2016 and total acidity in 2017 showed significant differences based on different degrees of water stress. Secondary metabolites were characterized with a C18 reversed-phase HPLC. The results indicated that peonidin was the most dominant anthocyanidin form in Crimson Seedless table grape. There was no difference in anthocyanidins in 2016. However, delphinidin, petunidin, and malvidin were greater in content within the relatively higher water stress cluster. This study provides evidence to optimize the application of proximal sensing to monitor, estimate, and manage on-site measurements of plant water status, productivity, and berry chemistry in a large-scale vineyard.

Funding Support: USDA-NIFA Specialty Crops Research Initative