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

Annual rings from vines in a 30 year old, 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 measured at the
beginning and end of the lifetime of the vineyard. 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 thereafter, consistently shortening ring width
throughout the lifetime of the vine. The ratio of yield to vegetative
growth, juice pH, photosynthetic assimilation and transpiration rates, and
stomatal conductance are correlated with scion trunk radius. Rootstocks
modulate secondary growth over years, altering hydraulic conductance,
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.