CHANGES IN LIPID-COMPOSITION AFTER IN-VITRO SELECTION FOR GLYPHOSATE TOLERANCE IN TOBACCO

After a one-step selection procedure with glyphosate added to the call us medium, tobacco regenerants were obtained from calluses surviving o n field doses of the herbicide. The lipid and sterol compositions of p otted plants from the two original cultivars which underwent the selec tion procedure but without glyphosate, and the selected regenerants we re investigated. Controls were derived from micropropagation and not f rom seeds. They served as appropriate controls for comparison with gly phosate regenerants, i.e. they underwent exactly the same experimental conditions except for the glyphosate treatment. Plant regeneration wa s strongly (at one-step selection) or fully (at stepwise selection) in hibited. Only a few glyphosate-tolerant plants (seven of Nevrokop A(24 ) and five of Zlatna arda) were obtained which were cloned and potted. At least 10 plants of one clone per genotype were used for the furthe r biochemical analyses. The spraying of the tobacco plants from the cu ltivars with glyphosate led to a decrease of monogalactosyl diacylglyc erol content and increase of the saturated fatty acids in all glycolip id classes. The concentration of stigmasterol increased and that of si tosterol decreased only in Zl.arda variety. In the regenerants there w ere different changes in lipid composition, concerning mainly a decrea se of monogalactosyl diacylglycerols (MGDG) and an increase of digalac tosyl diacylglycerols (DGDG) in Zl.arda-derived regenerants and increa se of the amounts of neutral lipids and decrease of phospholipids (PL) in the Nevrokop A(24)-derived regenerants. Surprisingly, after treatm ent of the regenerants with glyphosate, the MGDG amounts in these rege nerants were higher than in the controls, which could mean a lesser ab ility to control ion permeability.