NaCl salinity stress decreased Bacillus thuringiensis (Bt) protein content of transgenic Bt cotton (Gossypium hirsutum L.) seedlings

Seedling responses of two transgenic Bacillus thuringiensis (Bt) cotton (Gossypium hirsutum L.) cultivars, 99B and SGK9708-41, to salinity stress were studied under 0, 50, 100 and 200 mM NaCl treatments. Cotton seedling growth, indicated by height, leaf area, and fresh and dry weights, of both cultivars was reduced by NaCl in a concentration-dependent manner. Total N concentrations of seedling roots, stems and leaves of both cotton cultivars decreased with increasing NaCl concentrations. For both cultivars, soluble protein content increased in leaves and decreased in stems due to salt stress, and decreased in roots by 50 and 100 mM NaCl. Bt protein concentrations in leaves of both cultivars were decreased by salt stress, but still were biologically effective to control the neonate bollworm larvae in seedling cotton.