Chemical Mutagenesis—A Promising Technique to Increase Metal Concentration and Extraction in Sunflowers

Abstract

Since most of the metal-hyperaccumulating wild plants only produce very low biomass and many high-yielding crops accumulate only moderate amounts of metals, the current research is mainly focused on overcoming these limitations and the optimization of metal phytoextraction. The main goal of the present study was the improvement of metal concentration and extraction properties of Helianthus annuus L by chemical mutagenesis (the non-GMO approach). Sunflowers—hybrid cultivar Salut and inbred lines—were treated with the chemical mutagen ethyl methanesulfonate (EMS). The effect of chemical mutagenesis on metal concentration in and extraction by new sunflower M₁ and M₂ mutants was directly assessed on a metal-contaminated field in Rafz, Switzerland. Mutants of the M₂ generation showed a 2–3 times higher metal shoot concentration than the control plants. The best M₂ sunflower “giant mutant” 14/185/04 showed a significantly enhanced metal extraction ability: 7.5 times for Cd, 9.2 times for Zn, and 8.2 times for Pb in aboveground parts, as compared to the control plants. Theoretical calculations for the phytoextraction potential of new sunflower variants note that the best sunflower mutant can produce up to 26 t dry matter per hectare and remove 13.3 kg Zn per hectare and year at the sewage sludge contaminated site of Rafz; that is a gain factor of 9 compared to Zn extraction by sunflower controls. Furthermore, the use of sunflower oil and biomass for technical purposes (lubricants, biodiesel, biogas) should produce an additional value and improve the economical balance of phytoextraction.

KEY WORDS::

• Helianthus annuus L.
• mutagenesis
• ethyl methanesulfonate
• phytoextraction
• metal concentration
• non-GMO approach

ACKNOWLEDGMENTS

This work was part of the EU-Framework Programme Quality of Life and Managing of Living Organisms (QLRT-2001–00429). PHYTAC-Development of Systems to Improve Phytoremediation of Metal Contaminated Soils Through Improved Phytoaccumulation and was financed by the SBF (Staatssekretariat für Bildung und Wissenschaft), Berne, Switzerland. The authors also acknowledge the valuable assistance of Peter Baur and Reinhard Schweizer, farmer and landowner of the Rafz site, and Werner Stauffer and Satish Gupta from Agroscope FAL at Berne-Liebefeld.