Grapevine (Vitis vinifera L., cv. Pinotage) responses to water deficit modulated by rootstocks

[摘要] ENGLISH ABSTRACT: Water scarcity is a key limiting factor for viticulture in dry regions. Traditionally droughtsensitive varieties have the potential to grow in dry areas, however in most situations, throughthe use of rootstocks. Drought-tolerant rootstocks are expected to improve grapevine response towater deficit by improving the water uptake and transport and by reducing the water loss inleaves by root-to-shoot signalling. The mechanisms of rootstocks' tolerance to drought are notyet fully understood. The main aim of this study was to improve the understanding of therootstock/scion-cultivar interaction in the regulation of grapevine water use and leaf stomatalbehaviour. Irrigated field vines without any water constraint were compared to rain-fedgrapevines subjected to moderate water constraint. To better manage vine water status, reducevariability, and compare more rootstocks, greenhouse trials were also conducted where plantswere well watered or subjected to severe water constraints. Pinotage grapevines (Vitis viniferaL.) grafted onto 110 Richter, 140 Ruggeri and 1103 Paulsen rootstocks were used for fieldexperiments whereas Pinotage grapevines grafted onto 99 Richter, 110 Richter, 140 Ruggeri,1103 Paulsen and Ramsey were used for greenhouse experiments. Our study suggested theinfluence of rootstocks on scion-cultivar water status and leaf stomatal size and density and gasexchange of the scion, implying an influence on water uptake and transport and a tight regulationof the stomatal conductance. Our data supported the hypothesis that the influence of rootstock inresponse to drought seemed to be higher under increasing water deficit up to a point where theplant water status is the main driver of the stomatal conductance and therefore photosynthesisregulation, considering the plant water status thresholds. In addition, the results suggested thatstomatal development is affected by light, drought and possibly by rootstocks. Nevertheless, it isstill not clear how the rootstock affects stomatal development and the link with scion-cultivarwater use. It seems that the transpiration rate of leaves is more related to stomatal size thandensity. Thus one possible mechanism of Pinotage leaf adaptation to water constraints wasstructural during leaf growth, with a reduction in pore size to reduce plant water loss. The resultsshowed that the rootstock is regulating the cultivar's stomatal size (anatomical changes duringleaf growth) and functioning (stomatal regulation) through a complex signalling process. Theeffect of light on stomatal development is interesting in the context of canopy microclimate andcanopy manipulation (choice of the vine architecture vs canopy size, in the context of climatechange versus the possible increase in drought and water scarcity). The use of rootstocks is along term investment which aims to provide resistance to soil pests and pathogens and to conferto the scion-cultivar drought and salt tolerance. The use of drought tolerant rootstocks is actually one of the most relevant practical solutions in dry terroir – units and in situations where wateravailability is limited. The understanding of the physiological and genetic mechanisms whichgovern scion-cultivar drought tolerance/behaviour induced by rootstocks is critical in terms ofrootstocks choice in interaction with the scion-cultivar and is critical to assist breeding programsto create/select drought tolerant rootstocks.

[发布机构] Stellenbosch University