<i>In vitro</i> inhibition of soil microorganisms by 2‐phenylethyl isothiocyanate

Abstract

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 (ED 90 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.