Phenotypic evaluation of 'thompson seedless' grapes transformed with atnhx1 growing in hydroponics and potted soils

Overexpression of vacuolar Na+/H+ antiport AtNHX1 has been reported to improve plant salt tolerance. We produced transgenic plants of Vitis vinifera ?Thompson Seedless? via Agrobacterium tumefaciens carrying the gene encoding for AtNHX1 under the control of the constitutive promoter CaMV35S. Independent transgenic lines with improved tolerance to salt stress were selected in first round evaluations. The objective of this study was to analyze the response of the selected lines to NaCl stress in hydroponics and potted soils. Untransformed and transgenic plants were acclimated to greenhouse conditions and grown hydroponically using Long Ashton nutrient solution. In the salinity treatments, NaCl concentrations were increased stepwise by 25 mM every 10 days up to 150 mM. In addition, untransformed and transgenic plants were grown in a mix of 7-3 grape pomace-sand soil and watered with Long Ashton nutrient solution with and without increasing concentrations of NaCl. Analysis of plant growth variables confirmed the improved tolerance of the transgenic lines, which showed higher shoot length, leaf number, leaf area, and fresh and dry weight of shoots and roots. However, their improved performance was not correlated with higher Na accumulation in root and/or shoot tissue compared to the untransformed controls. Na and Cl tissue contents were higher in plants grown in hydroponics; and roots accumulated 1.5-2.5 times more NaCl than aerial parts