Rootstock effect on irrigated grapevine yield under arid climate conditions are explained by changes in traits related to light absorption of the scion

- Grapevines grafted on vigorous rootstocks modify light capture traits including chlorophylls, Lhcb2, leaf area, SLA and LAI (assessed via pruning weights).
- These responses are linked to higher assimilation capacity by the scion of grafted plants promoting a higher amount of sugar in leaves, earlier onset of carbon storage in roots and enhanced yield.
- Even under the arid conditions of the experimental plot, water relation traits including WUE, transpiration, stomatal conductance and RWC were unrelated to the performance of rootstocks.
- Considering the results Salt Creek and Harmony are the most efficient rootstocks under these conditions.

The purpose of this study was to investigate the mechanisms underlying the effect of rootstocks on table grapevines grown under irrigated conditions in the arid North macro-zone of Chile.Grapevine cv. Red Globe grafted onto three rootstocks (Harmony, Saint George and Salt Creek) were studied Structural and physiological parameters were monitored at different phenological stages under optimal production conditions.An outstanding yield increment brought about by the rootstocks Harmony and Salt Creek was correlated with increased individual leaf and specific leaf area, pruning weight (proxy for total leaf area), photosynthesis per unit leaf mass, sugar in leaves and root carbon reserves. In addition, these high yielding rootstocks induced higher contents of light-harvesting chlorophyll a/b protein of photosystem II and total chlorophyll in the leaves of the scion. No correlations of yield with traits involved in water use (relative water content or instantaneous water use efficiency) were observed.The effects of rootstocks on the light capture capacity of the scion directly affected carbon assimilation and storage and, accordingly, yield. Therefore, the identified traits are valuable targets for screening and selecting yield efficient rootstocks for irrigated table grape production in arid zones.