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Characterization of drought-tolerant sugar beet mutants induced with gamma radiation using biochemical analysis and isozyme variations.

BACKGROUND
In this study, drought-tolerant mutants of sugar beet (Beta vulgaris L. cv. Felicita) were obtained by in vitro mutagenesis and characterized by biochemical analysis and isozyme variations.


RESULTS
Among the M₁V₃ plantlets, drought-tolerant mutants were selected on MS medium supplemented with 10⁻² and 2×10⁻² kg L⁻¹ PEG6000. As a result of biochemical analyses, drought stress stimulated SOD activity in eight out of ten mutants compared with the control. APX activity was enhanced in four out of ten mutants (M5, M8, M9 and M10), whereas POX and CAT activities increased significantly in all mutants. Additionally, FRAP values and chlorophyll (a+b, a and b) and carotenoid contents were enhanced under stress conditions in all mutant plants compared with the control. As for isozyme variations, two new POX isozyme bands (POX5 and POX1) were detected in all mutants but not the control, and Fe-SOD was observed in one out of ten mutants (M8), while the intensity of Cu/Zn-SOD was found to be variable in all experimental samples. Furthermore, CAT and APX isozymes were detected at different intensities on native gels.


CONCLUSION
In vitro mutagenesis is a useful technique for improving plant tolerance against environmental stresses.