In vitro inhibition of soil microorganisms by 2-phenylethyl isothiocyanate

Isothiocyanates (ITCs) are produced by the enzymatic hydrolysis of glucosinolates in cruciferous plants and can kill fungi, oomycetes and bacteria. The effect of 2-phenylethyl ITC (2-PE ITC), the main ITC liberated from the roots of canola, was tested in vitro on a range of fungi, oomycetes and bacteria. Bacteria were generally more tolerant than the eukaryotic pathogens to 2-PE ITC, although both groups showed considerable variability in response (ED₉₀ ranging from 0·005 to 1·5 m m for eukaryotes, and from 0·33 to greater than 3·34 m m for complete inhibition of bacterial growth). While intraspecies variability was low, interspecies variability was high within some genera. Amongst the eukaryotes, Trichoderma spp. were the most tolerant to 2-PE ITC, while other genera, including Aphanomyces , Gaeumannomyces , Phytophthora and Thielaviopsis , were very sensitive. A range of responses was exhibited by Pythium spp. and the different anastomosis groups of Rhizoctonia solani . A simple laboratory screening may be an effective way to identify candidate soilborne pathogens for control in rotation cropping systems which include a Brassica crop phase.