Cross-enhancement: enhanced biodegradation of isothiocyanates in soils previously treated with metham sodium |
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| Authors: | Ben Warton John N MatthiessenMark A Shackleton |
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| Institution: | CSIRO Entomology, Private Bag 5, Wembley, WA 6913, Australia |
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| Abstract: | Rates of degradation of 2-propenyl isothiocyanate (PrITC), benzyl isothiocyanate (BeITC) and 2-phenylethyl isothiocyanate (2-PeITC) in a soil known to biodegrade methyl isothiocyanate (MITC) at an accelerated rate, but never previously exposed to the other ITCs, were higher (persistence in soil increased by 1150, 80 and 100%, respectively,) than in a similar non-degrading soil. The rate of degradation of the same three ITCs was significantly lower in sterilised (autoclaved) soils than in the degrading soil. These results indicate that the three ITCs are susceptible to enhanced cross-biodegradation in soils where enhanced biodegradation of MITC has been induced by use of metham sodium soil fumigant. When Brassica plant tissue containing sinigrin (2-propenyl glucosinolate) as the predominant glucosinolate (GSL) was added to the degrading soil, the amount of PrITC present after 24 h was significantly lower than in the non-degrading soil at the same amendment rates. The toxicity to an insect test organism of the PrITC produced from the biofumigant plant tissue was correlated with the concentration of PrITC measured in the two soils, with 67% more plant tissue required in the degrading soil to cause 100% mortality as in the non-degrading soil (3.0 vs 5.0 mg g−1). The effectiveness of biofumigation using ITC-producing Brassica plants may be diminished in soil suffering from enhanced biodegradation of MITC. |
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| Keywords: | Cross-enhancement Isothiocyanates Metham sodium Brassica Enhanced biodegradation |
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