X-ray imaging of 30 year old wine grape wood reveals cumulative impacts of rootstocks on scion secondary growth and Ravaz index

Abstract

Annual rings from 30 year old vines in a California rootstock trial were measured to determine the effects of 15 different rootstocks on Chardonnay and Cabernet Sauvignon scions. Viticultural traits measuring vegetative growth, yield, berry quality, and nutrient uptake were collected at the beginning (1995 to 1999) and end (2017 to 2020) of the lifetime of a vineyard initially planted in 1991 and removed in 2021. X-ray Computed Tomography (CT) was used to measure ring widths in 103 vines. Ring width was modeled as a function of ring number using a negative exponential model. Early and late wood ring widths, cambium width, and scion trunk radius were correlated with 27 traits. Modeling of annual ring width shows that scions alter the width of the first rings but that rootstocks alter the decay of later rings, consistently shortening ring width throughout the lifetime of the vine. Ravaz index, juice pH, photosynthetic assimilation and transpiration rates, and instantaneous water use efficiency are correlated with scion trunk radius. Ultimately, our research indicates that rootstocks modulate secondary growth over years, altering physiology and agronomic traits. Rootstocks act in similar but distinct ways from climate to modulate ring width, which borrowing techniques from dendrochronology, can be used to monitor both genetic and environmental effects in woody perennial crop species.

Figure 1

Grapevine rings and scion trunk radii. A) X-ray CT cross-section through a grapevine trunk. Along a line from the center of the pith to bark, landmarks are placed indicating early (darker shade color) and late (lighter shade color) wood, the remaining outer rings, and cambium. B-C) Boxplots showing distributions of scion trunk radii (cm) in B) Chardonnay (solid) relative to Cabernet Sauvignon (transparent) and number of Chardonnay vines measured and C) Cabernet Sauvignon (solid) relative to Chardonnay (transparent) and number of Cabernet Sauvignon vines measured.

Figure 2

Models of ring width. A) For the negative exponential model, the overall model fitted to all the data (black solid line) and models fitted with values +1.5 standard deviations (solid lines) and − 1.5 standard deviations (dashed lines) for (magenta lines), (blue lines), and (orange lines).B-D) Boxplots of model values by rootstock and by scion for B), C), and D). Cabernet Sauvignon is indicated by purple and Chardonnay by green.

Figure 3

Comparison of ring width models by scion and rootstock. A) A swarmplot of all measured ring widths for Chardonnay (green) and Cabernet Sauvignon (purple) with an overall model (black) and models for each scion, B) models for each vine measured colored by scion, C) models for each rootstock for Chardonnay scions, and D) models for each rootstock for Cabernet Sauvignon scions. Rootstocks colored as indicated.

Figure 4

Correlations between ring features and traits. A) Boxplot showing distributions of Spearman’s rank correlation coefficient values for correlation between indicated traits for Chardonnay (green) and Cabernet Sauvignon (purple) and scion trunk radius (cm). B) 26 correlations that remain significant at p < 0.05 after Benjamini-Hochberg multiple test correction. The year, scion, and trait as well as ring features (modeled values, early ring widths, late ring widths, outer ring width, or total width) are indicated. Negative (burnt orange) to positive (violet) correlation coefficient values are indicated by scale and also provided by text for each correlation.

Figure 5

Correlations by year for Ravaz index and pH with scion trunk radius. Asterisks indicate significant correlations (as indicated in Figure 4B), based on multiple testing correction. For correlations between A) Ravaz index and B) juice pH correlations with scion trunk radius (cm) for data from each scion and indicated year (black data points) and a modeled trendline (blue) are superimposed over all data for the trait (Chardonnay, green; Cabernet Sauvignon, purple) across the years shown.

Figure 6

Repeated measures correlation between physiological traits and scion trunk radius for three rootstocks. Repeated measure correlation coefficient (rrm) and p value are shown for the overall fitted correlation between A) A, assimilation rate (μmol m-2 s-1), B) E, transpiration rate (mol m-2 s-1), C) WUEi (A/E) instantaneous water use efficiency (μmol/mol x1000), and D) leaf temperature (oF) with scion trunk radius (cm) across 3 rootstocks measured on 15 dates across two years. The scions and rootstocks (T = Teleki 5C, F = Freedom, and P = 1103 Paulsen) are indicated in the top panels and dates are indicated as shown by color, yellow shades for 2018 and blue for 2019.