Suppressive activity of some glucosinolate enzyme degradation products on Pythium irregulare and Rhizoctonia solani in sterile soil

Glucosinolate degradation products (GLDPs), mainly isothiocyanates, obtaine d by myrosinase-catalysed hydrolysis of glucosinolates (GLs), are an import ant group of natural bioactive substances. The fungitoxic activity of four GLDPs, chosen on the basis of their side-chain structures, was assayed agai nst Pythium irregulare and Rhizoctonia solani. The effectiveness of the deg radation products (DPs) of sinigrin (alkenyl GL), epi-progoitrin (hydroxy-a lkenyl GL), glucoiberin and glucoerucin (thiofunctionalised GLs) in inhibit ing P irregulare oospore germination and R solani soil colonisation were te sted in a closed system, using an artificially infected soil. The fungitoxi c activity of these GLDPs varied according to their side-chain structure. A s in previous in vitro studies, the thiofunctionalised GLDPs were found the most effective, producing complete inhibition of P irregulare oospore germ ination (0.01 mu mole g(-1) soil) and R solani soil colonisation (0.5 mu mo l eg(-1) soil), but even sinigrin DP showed a fungitoxic activity higher th an that of epi-progoitrin DP. (C) 2000 Society of Chemical Industry.