Shijian Zhuang,* Matthew Fidelibus, Kaan Kurtural, and Nick Davis 
*University of California Cooperative Extension, 550 E Shaw Ave, Suite 210-B, Fresno, CA 93710 (gzhuang@ucanr.edu)

San Joaquin Valley (SJV) has 61% of Pinot gris acreage and the majority of Pinot gris crush volume (83%). Strong demand for this cultivar has encouraged growers to advance the time frame from planting to production to less than two years. This requires the permanent vine structures to be established in the first year, with the first crop expected in the second year. Cropping in the second year raises the risk of overcropping, with possible carryover effects in subsequent years. To identify the optimum crop level and economic threshold for young Pinot gris vines, a field trial was conducted in a commercial vineyard in Fresno, CA. Three levels of inflorescences were retained three weeks before bloom at 0, 1/2, and 1 inflorescence per shoot, and unthinned vines were used as a control. Fruit ripening was significantly advanced by thinning inflorescences prebloom. Yield was reduced by 100, 28, and 6% from the thinning. Yield compensation was associated with greater fruit set and berry mass, without rot issues. Total soluble solids at harvest was significantly lower in the control vines. Pruning weight was significantly affected, ranging from 0.46 to 1.18 kg/vine, and the Ravaz index (RI) ranged between 8.3 and 19.9. Based on our results in 2016, 4.2 kg/m row and 0.45 kg/m row are believed to be the yield level and pruning weight for young Pinot gris vines under the quadrilateral cordon spur-pruning system to achieve an RI of 10. This pilot study provides evidence that this yield level and canopy size can give winegrape growers the maximum yield without affecting fruit quality and the following year’s crop. Yield and canopy data in 2017 and 2018 will continue to be collected to understand possible carryover effects.

Funding Support: UCCE and The Wine Group