Assessing visualized response phenomena of grapevine rootstocks exposed to lime and drought stress

Vinifera EuroMaster - European Master in Viticulture and Oenology Engineering / Instituto Superior de Agronomia. Universidade de Lisboa / University of Natural Resources and Life Sciences, Vienna

Iron-deficiency induced chlorosis and drought stress are major constraints in viticulture influencing grape yield and quality. Notably when occurring simultaneously, these stresses can have intense negative effects on plant physiology and plant nutrition. Grapevine rootstocks have the capacity to adapt to different abiotic stresses by morphological, biochemical or gene expression changes, but the mechanisms in detail are not well studied. It can be assumed, that root differentiation has a functional key role in rootstocks adaptation to abiotic stresses. Therefore, the current study aims to characterize the Casparian strip formation and the suberization of endodermis and exodermis to conclude on the plasticity in nutrient and water uptake of grapevine rootstocks. In in-vitro approaches Fercal and 3309 C were subjected to iron free growth conditions and osmolyte induced drought stress as well as the combined stress. Furthermore, rootstock cuttings were grown in rhizoboxes to evaluate the root system architecture. For the intra-treatment comparison, significant differences in root pattern distribution and length parameters were found. For the rootstocks compared, intensified main root length growth seemed not to be a mitigative strategy. In contrast, Fercal had significantly fewer and shorter lateral roots than 3309 C. This implies, Fercal is more efficient per unit root surface. i.e. by increasing the area of the root hair zone. A systematic lignification and suberization can incrementally be observed with increasing stress intensity. For 3309 C, the rhizobox experiments also showed intra-treatment effects. For iron deficiency, foraging seemed to be the main strategy. The results confirmed a high variability between rootstocks supposing specific adaptations strategies to no-iron and drought stress conditions on the root system development as well as on the root molecular differentiation process. The established in-vitro based method could provide a tool to test different environment versus genotype interactions of grapevine rootstocks

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