Differential physiological responses of Tunisian wild grapevines (Vitis vinifera L. subsp. sylvestris) to NaCl salt stress

The effects of salt stress on growth, organic and inorganic solute accumulation and chlorophyll florescence were studied on 3-month-old plants of six Tunisian wild grapevine accessions in order to identify salt tolerance mechanisms and select tolerant genotypes. Potted plants were grown under controlled conditions and irrigated for 14 days with 0, 100 and 150 mM NaCl Long Ashton nutrient solution. Salt begins to adversely affect plant growth and plant nutrition at 100 mM NaCl. Compared to control, shoot growth rates were 21.5% less for Khedhayria, Tebaba and Ouchteta, 33% for Djebba and Zouarâa and 49% for Houamdia. They were assigned to stomatal and non-stomatal factors. Stomatal conductance decreased after 1 day at 150 mM NaCl in all accessions in response to reduced leaf water potential. Leaves in tolerant accessions were well hydrated through efficient osmotic adjustment, sufficient potassium flux and selectivity of K+ versus Na+. In addition, salt tolerance of wild grapes was related to limiting Na+ transport to lamina and to compartmentalization of Cl− on root and leaf vacuoles, improved in Tebaba and Khedhayria by the uptake of K+. At the same time, disturbances of the PSII have been noted as non-stomatal factors, and the most important photoprotective mechanism against photosynthetic damages was non-photochemical energy dissipation. However, chlorophyll fluorescence parameters were more stable in Tebaba compared to Khedhayria, thus showing better salt tolerance. Based on our results, wild grapevine accessions could be classified from most tolerant to most sensitive as follows: Tebaba > Khedhayria > Ouchteta > Zouarâa > Djebba > Houamdia.