Partner und Internationale Organisationen
(Englisch)
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AT, BE, GB, CH, CZ, DE, DK, EE, ES, FI, FR, GR, HU, IE, IL, IT, LT, LU, NL, NO, PL, PT, RO, SE, SI, SK, TR, UK
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Abstract
(Englisch)
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Within COST Action 859 the most efficient genotypes of sunflower mutants of M3 and M4 generations with improved yield and metal removal efficiency and specific cultivation methods were carefully assessed and a field-based mutant screening on a sewage sludge contaminated site in Rafz (CH), located near Zuerich airport, was continued in 2005-06. The aim was to optimise and validate the 'improved phytoextraction technique' and to bring this sustainable remediation procedure towards a practical use. These promising sunflower mutants (self-pollinated inbredlines) with strongly enhanced metal extraction characteristics were previously obtained from Project 'PHYTAC' of EC 5th Framework Programme (2002-2005) by means of chemical mutagenesis and a field based mutant screening. The results of the first field-based mutant screening of 500 promising sunflower M3-mutants, within COST Action 859 in 2005, showed three differing groups of sunflower mutants with alterations in growth and metal uptake: (1) sunflower mutants with a significantly enhanced biomass production and no change in metal accumulation; (2) mutants with an enhanced biomass and metal accumulation and extraction; and (3) mutants with a reduced metal accumulation (exclusion) in the shoots. The metal extraction of the promising 2nd group of most efficiently yielding and metal extracting sunflower mutants, showed in M3 generation enhanced gain factors as follow: yield 2.5-5 fold, Cd 2.4-4.8 fold, Zn 2.3-6.2 fold, and 6-17 fold for Pb extraction, that is a valuable sign of genetically stable mutants. The second field experiment in Rafz in 2006 was aimed on the screening of the top-ten sunflower mutant-lines for their metal extraction efficiency in 4th generation (300 individual sunflower mutants). The improved growth and metal accumulation/extraction characteristics were assessed for each sunflower mutant-line individually to find out the most efficiently yielding and metal extracting sunflower mutants of M4 and to follow up their genetic stability under real field condition. The most promising M4 sunflower mutant 17/67-35-190-04 produced a 4.7 fold enhanced biomass, a 3.5 fold Cd, 4.7 fold Zn, 7.1 fold Cr, and a 8.3 fold Pb extraction, as compared to the non-mutagenized control IBL 04. Theoretical calculations of the phytoextraction efficiency of this strongly enhanced M4 sunflower mutant 17/67-35-190-04 and its control IBLO4 show the following results: the [BL 04 control produced 4.7 t dry matter yield per ha and year and could remove 2.4 kg Zn, 18 g Pb and 7 g Cd on the Rafz field, whereas the enhanced M4 sunflower mutant 17/67-35-190-04 produced up to 20.9 t dry matter yield and could remove 11 kg Zn, 147 g Pb and 25 g Cd per ha and year. In M4 population other promising sunflower mutants with a high phytoextraction efficiency were also found. One of them, sunflower mutant 6/15-35-190-04 can remove 16.6 kg Zn, that is 6.9 fold more efficient, as compared to the control IBL 04. Moreover, several sunflower mutants of 4th generation and control IBL 04 plants, were separately analysed for Cd, Zn and Cr concentration in roots, shoots, leaves, flower and seeds. This study of metal distribution showed a strong effect of chemical mutagenesis on metal translocation and accumulation in individual plant organs. Some sunflower mutants showed a higher metal concentration in leaves, for example M4 mutant 1/86-35-190-04 accumulated 39 % of total Cd and 59 % of Zn in the leaves, whereas seeds showed a marginal Cd and Zn concentration (5-8%). The gain factors for the leaves are as follow: Cd 1.3, Zn 2, yield 1.9 fold, as compared to the control IBL04. Beside sunflower mutants with enhanced metal concentration in shoots, mutants with enhanced root accumulation were also found. M4 sunflower 1/43-14-185-04 accumulated in roots 1.3 fold Cd, 1.6 fold Zn, 1.7 fold Cr and Pb, as compared to the IBL 04. Zinc efficient sunflower mutant lines, were additionally assessed on a Zn contaminated site in the eastern part of Switzerland and the results of yield, metal accumulation and extraction were compared with data of the field experiments in Rafz in 2005 and 2006. M3 sunflower mutant line 8-185-04, tested in 2005 at both sites and M4 sunflower 15-35-190-04, tested in 2006, provided an enhanced yield and metal removal efficiency by a factor of 4-5 at both contaminated sites. Based on the results of now four sequencial mutant screenings and the metal removal efficiency of most of the promising sunflower mutants until the 4th generation, we can conclude, that chemical mutagenesis mainly affected yield and metal extraction characteristics, and partially metal accumulation in aerial plant parts. The high biomass production makes the sunflower mutants very interesting for the 'improved phytoextraction' of metals from contaminated soil. Compared to GMOs, our improved sunflower mutants (non-GMO) are free from any restrictions for freeland application. In addition, a negligible concentration of toxic metals in sunflower seeds and oil should lead to added value products, such as the use of sunflower oil for the sustainable (CO2-neutral) energy production (biodiesel) and for technical lubricants.
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