Abstract: To evaluate the effects of combined salt tolerant mechanisms, BADH gene from Atriplex hortensis was introduced into the T2 generation of transgenic tomato (L. esculentum 'Moneymaker') line X1OEA1 containing AtNHX1 by Agrobacterium tumefaciens mediated transformation. PCR, Southern blot, RT-PCR and betaine measurement indicated that BADH was integrated into the genome of X1OEA1 and functioned properly. Physiological responses of the double transformant to 200 mmol·L-1 NaCl treatment, reflected by photochemical efficiency of PSⅡ(Fv/Fm), relative electronic conductivity (Rc/Rc'), chlorophyll content (Chla+b, Chla/b) and net photosynthetic rate (Pn), were better than those in X1OEA1. The double gene transformed tomato TT0-2 showed the least decrease of Fv/Fm value while the salt concentration increased gradually, and the relative electronic conductivity of TT0-2 and X1OEA1 line T2 plant were 3.6 and 4.2 times higher under 200 mmol·L-1 NaCl treatment compared with normal condition. The stem's dry weight and fresh weight of TT0-2 were 12.5% and 19.8% higher than that of X1OEA1 line T2 plant, respectively, at the same time, the leaves' dry weight and fresh weight of which were 22.5% and 14.0% higher. The results indicated that multigene transformation could further improve salt tolerance of plant. Furthermore, the transformation system of tomato was optimized. The results have proved that Timentin is a better antibiotic than cefotaxim for the effective transformation of tomato.

Key words: Agrobacterium tumefaciens, BADH, AtNHX1, Double-gene transformation, Salt-tolerance, Tomato