In vitro 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.

Exogenous glucosinolate produced by Arabidopsis thaliana has an impact on microbes in the rhizosphere and plant roots

“…Differential effects on microbial populations that we observed could result from variable direct susceptibility of populations towards antimicrobial properties of hydrolysis products of glucosinolates (Smith and Kirkegaard, 2002;Kliebenstein et al, 2005;Brader et al, 2006). Beside their antimicrobial effect, glucosinolates and their hydrolysis products could also stimulate microbial growth.…”

“…Fungi modifications are expected according to literature. They were reported to be more sensitive than bacteria to these compounds (Smith and Kirkegaard, 2002). The formation of antimicrobial products from glucosinolates has been also suggested to explain the inability of Brassicaceae plants to form arbuscular mycorrhizal (Vierheilig et al, 2000;Roberts and Anderson, 2001).…”

“…The effects on fungal and bacterial responses of the glucosinolate-myrosinase defense system have already been described. However, these studies implicated pure strains of pathogen organisms and in vitro approaches (Brabban and Edwards, 1995;Kirkegaard et al, 1996;Smith and Kirkegaard, 2002;Souza-Fagundes et al, 2004). The incorporation of crucifer tissues showed a variety of effects on non-target soil microbial populations in studies based on isolation and culture of microorganisms (Scott and Knudsen, 1999;Bending and Lincoln, 2000;Cohen et al, 2005).…”

Effects of Plant Residue, Root Exudate and Juvenile Plants of Rapeseed (Brassica napus L.) on the Germination, Growth, Yield, and Quality of Subsequent Crops in Successive and Rotational Cropping Systems

“…The presence of glucosinolates in root tissues can reduce the growth of fungi and oomycetes (Smith and Kirkegaard, 2002). Larkin and Griffin (2007) reported that when rapeseed was grown as a green manure crop, it reduced powdery scab infections in a subsequent potato crop.…”

Changes in fungal communities in organically fertilized soil

“…However, Smith and Kirkegaard (2002) found out that species of Trichoderma genus are tolerant to the above compounds. Curl (1982) even stated that plant excretions can improve the phytosanitary condition of soils through a better development of fungi inhibiting the growth of pathogens.…”