Improved salt-tolerance of transgenic soybean by stable over-expression of AhBADH gene from Atriplex hortensis

The salt-tolerance of transgenic soybean cleared for environmental release was improved by stable over-expression of AhBADH gene from Atriplex hortensis, which was demonstrated through molecular analysis and field experiments. An effective strategy for increasing the productivity of major crops under salt stress conditions is the development of transgenics that harbor genes responsible for salinity tolerance. Betaine aldehyde dehydrogenase (BADH) is a key enzyme involved in the biosynthesis of the osmoprotectant, glycine betaine (GB), and osmotic balance in plants, and several plants transformed with BADH gene have shown significant improvements in salt tolerance. However, very few field-tested transgenic cultivars have been reported, as most of the transgenic studies are limited to laboratory or green house experiments. In this study, we demonstrated through field experiments that AhBADH from Atriplex hortensis confers salt tolerance when transformed into soybean (Glycine max L.). AhBADH was successfully introduced into soybean by Agrobacterium mediated transformation. A total of 256 transgenic plants were obtained, out of which 47 lines showed significant enhancement of salt tolerance compared to non-transgenic control plants. Molecular analyses of the transgenic line TL2 and TL7 with the highest salt tolerance exhibited stable inheritance and expression of AhBADH in progenies with a single copy insertion. TL1, TL2 and TL7 exhibited stable enhanced salt tolerance and improved agronomic traits when subjected to 300mM NaCl treatment. Currently, the transgenic line TL2 and TL7 with stable enhanced salt tolerance, which have been cleared for environmental release, are under biosafety assessment. TL 2 and TL7 stably expressing AhBADH could then be applied in commercial breeding experiments to genetically improve salt tolerance in soybean.