Effects of salinity on potassium absorption and expression of K+transporter genes at different concentrations of potassium in Grape (Vitis vinifera L.)

Grapevine is classified as a moderately sensitive plant to salinity. Hydroponically three grape genotypes (Vitis vinifera L.) were treated with different concentrations of KCl (0.1, 0.3, 0.5, 1, 5, 10 mM KCl) and NaCl (0, 25, 50,100 mM NaCl). Cl- and Na+ contents were significantly increased in different plant organs of all the genotypes under salinity. In this study, sensitive ('GhezelUzum'), tolerant ('Gharashani') and semi-resistant ('Chawga') grape genotypes were selected based on screening experiments under salinity. 'Gharashani' accumulated higher Na+ and Cl- in roots compared to the sensitive one. 'Chawga' accumulated high K+ similar to Na+ in root and shoot even at high salinity. Km calculation for K+ and Na+ uptake in root and shoot of 'Chawga' showed that K+ and Na+ compete to enter the plant through roots. Two KUP/KT/HAK-type potassium transporters are expressed highly in the grapevine during stress. VvK1.1 could play a major role in K+ loading into grape tissues. The expression of VvKUP1 and VvKUP2 transporters and VvK1.1 channel in roots of 'Chawga' genotype increased significantly (P < 0.05) at different KCl concentrations under salinity stress. Our results showed a significant difference between tolerant and sensitive genotypes and highlighted a strong relationship between the accumulation of specific transcripts and the degree of salinity tolerance.