UC Davis

Viticulturists and winemakers utilize wine grape cultivar clones in order to achieve specific goals related to yield, quality, and wine characteristics. Vitis vinifera cv. Petite Sirah, also known as Durif, is an important wine grape cultivar in California in the production of varietal wines and as a means to improve the color/tannic structure of red wines through blending. Four Petite Sirah clones (FPS01, FPS03, FPS04, and FPS05) were evaluated to compare their agronomic performance and grape and wine characteristics over the course of the 2021 growing season. Eighty vines of each of the four clones were each organized into four biological replicates in a randomized block design at the Robert Mondavi Institute vineyard (Davis, CA). Five vines per biological replicate were evaluated for vine water status, canopy density, ripening parameters, veraison progression, harvest must chemistry, and cluster condition. Clones were harvested at similar ripeness levels, yields determined, and winemaking performed in triplicate. Both the grape and wine phenolic profiles were determined by the Adams-Harbertson Assay and reversed-phase high-performance liquid chromatography (RP-HPLC). Grape and wine aroma profiles were determined by used head space-solid phase micro extraction-gas chromatography-mass spectroscopy (HS-SPME-GC-MS). Wine phenolic extraction during fermentation was monitored daily by spectrophotometric measurements. Results indicate that clones FPS01 and FPS04 may ripen and accumulate sugar quicker than FPS03 and FPS05 depending on the growing season. Grape must from FPS05 contained higher level of malic acid while FPS03 contained the lowest. FPS03 wines had least amount of phenolic compounds in comparison to other clones as they contained the lowest amount of flavan-3-ols, anthocyanins, and flavonols. Wines from FPS01 and FPS04 were higher in flavan-3-ols and flavonols respectively. Grapes and wines from each clone also showed differences in the composition of volatile compounds. Therefore, it can be stated that differences in chemical composition exist among Petite Sirah clones. In this specific year, these chemical differences did not translate to clear, significant differences in sensorial perception based on descriptive analysis.