Concentration- and time-dependent effects of isothiocyanates produced from Brassicaceae shoot tissues on the pea root rot pathogen Aphanomyces euteiches

摘要

Isothiocyanates (ITCs) hydrolyzed from glocosinolates (GSLs) in Brassicaceae tissue are toxic to soil organisms. In this study, the effect of aliphatic and aromatic ITCs from hydrated dy Brassicaceae shoot tissues on the mycelium and oospores of the pea root rot pathogen Aphanomyces euteiches was investigated. The profile and concentrations of GSLs in two test Brassicaceae species, Sinapis alba and Brassica juncea, and the ITCs from the dominant hydrolyzed parent GSLs were monitored. The concentrations of dominant ITCs and pathogen exposure time were evaluated in in vitro experiments. The greatest effect on the pathogen was observed from aliphatic ITCs hydrolyzed from B. juncea tissue, and the effect depended on the ITS concentration and exopsure time. ITCs were more effectively hydrolyzed from B. juncea GSLs than from S. alba GSLs; i.e., the ITC/GSL ratio was higher in B. juncea than in S. albatissue, giving a different release pattern. The release of phenylethyl isothiocyanate, which was common to both species, followed a pattern similar to that of the dominant ITC in each crop speices. This suggests that trait other than GSL content, e.g., plant cell structure, may affect the release of ITCs ans should therefore influence the choice of speices used for biofumigation purposes.