|Rosen, Carl - UNIVERSITY OF MINNESOTA|
|Kinkel, Linda - UNIVERSITY OF MINNESOTA|
|Cao, A - CHINA ACADEMY OF AG SCIEN|
|Tharayil, Nishanth - UC RIVERSIDE|
Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 18, 2009
Publication Date: October 23, 2009
Citation: Wang, D., C. Rosen, L. Kinkel, A. Cao, N. Tharayil, J. Gerik. 2009. Production of methyl sulfide and dimethyl disulfide from soil-incorporated plant materials and implications for controlling soil-borne pathogens. Plant Soil. 324:185-197. Interpretive Summary: Recent interest in methyl bromide alternatives research created renewed energy in biofumigation or using soil-incorporated plant materials to control soilborne pathogens and diseases. The mode of action of biofumigation is commonly believed to be the biocidal effect of glucosinolate compounds in plant tissues and their degradation products after mixed in the soil. One popular understanding is the release of volatile chemicals that have an isothiocyanate group so the pesticidal actions is compared to synthetic metam sodium products. A lesser known yet more dominant group of volatile compounds released in some biofumigation experiments includes methyl sulfide and dimethyl disulfide. The overall objective of this study was to, through a glasshouse and two field experiments, to quantify production of methyl sulfide and dimethyl disulfide gases and their effect on controlling soilborne fungal pathogens and nematodes. We found that gas concentrations of methyl sulfide and dimethyl disulfide were variable, dependent of plant species used in the experiments and ambient or soil temperature during the experiment. Efficacy against Verticillium dahliae in potato stem saps, Fusarium, and citrus nematodes was correlated to high total gas concentrations of dimethyl disulfide and methyl sulfide or simply the presence of the green manure in soils. Biofumigation or green manure also appeared to have increased populations of freeliving nematode, an indicator of soil health (e.g. healthier soil contains more freeliving nematodes).
Technical Abstract: Soil-incorporated plant materials have been associated with reduction in soilborne pathogens and diseases. Most credits have been given to secondary products of glucosinolate hydrolysis. Little is known about the production of volatile sulfur compounds and even less on their efficacy against soilborne pathogens. A glasshouse experiment and two field experiments were conducted to quantify production of methyl sulfide and dimethyl disulfide gases and their effect on controlling soilborne fungal pathogens and nematodes. Depending on plant species, headspace air concentrations ranged from 3 to 414 ng cm -3 for methyl sulfide and 0 to 100 ng cm -3 for dimethyl disulfide. Low values in colony forming unit of Verticillium dahliae in potato stem saps correlated to high total gas concentrations of dimethyl disulfide and methyl sulfide. Fusarium counts were significantly reduced after soil incorporation of white mustard and no control was found for Pythium. Soil populations of citrus nematodes were reduced and freeliving nematode increased after soil incorporation of white mustard. The study demonstrated measurable production of methyl sulfide and dimethyl disulfide gases in glasshouse and field environment and their beneficial effect on controlling soilborne pathogens.