Allelochemicals produced during glucosinolate degradation in soil

Abstract

A variety of plant pests are suppressed by the incorporation of cruciferous plant material into soil. Although this effect is attributed to decomposition of glucosinolates into toxic products, little is known concerning glucosinolate degradation in the soil environment. Arenas (30 × 18 × 8 cm) that contained soil amended with 30 g defatted winter rapeseed meal (Brassica napus L.)/kg soil on one half and unamended soil on the other were constructed. Isothiocyanate concentrations in the soil were measured using infrared analysis of CC14 extracts, and ionic thiocyanate (SCN(-)) using ion chromatography on aqueous extracts. Quantities were monitored during a 100-hr time period in conjunction with a wireworm bioassay. Isothiocyanate production reached a maximum of 301 nmol/g soil at 2 hr, but decreased by 90% within 24 hr. Production of SCN(-) reached a maximum of 180 nmol/g soil at 8 hr but persisted longer than isothiocyanate. Separate late instar wire-worms (Limonius infuscatus Mots.) were repelled by the presence of rapeseed meal in less than 24 hr even though the meal was shown in separate experiments not to be toxic. We propose that rapidly produced isothiocyanates are responsible for this repellency, but other products such as SCN(-) may play a role.

Potencial alelopático de extratos aquosos de genótipos de canola sobre Bidens pilosa

“…Entre os metabólitos secundários existentes nessas plantas estão os glucosinolatos (Norsworthy, 2003). A hidrólise dos glucosinolatos gera produtos voláteis, entre eles os isotiocianatos, que possuem acentuado efeito alelopático sobre uma série de espécies vegetais (Brown et al, 1991). Segundo Norsworthy & Meehan (2005), uma das principais características desse composto é sua atividade herbicida.…”

Revitalizing the winter turnip rape crop in the northern latitudes

“…Even though the seed meal of winter oilseed rape seems not to be toxic to wireworms (Limonius infuscatus Mots. ), it has a strong repellent effect that has been attributed to the release of isothiocyanates or possibly carbonyl sulfide, carbon disulfide and hydrogen sulfide (Brown et al, 1991). Little is known yet about the mechanisms underlying these observations and thus more research should be directed towards biofumigation.…”

“…Glucosinolates have limited biological activity, but their enzymatic hydrolysis results in the formation of allelochemicals (Brown et al, 1991). When glucosinolates come into contact with the enzyme myrosinase which catalyses their hydrolysis, one of the resulting compounds is isothiocyanate (Laegdsmand et al, 2007).…”

Cover Crops with Biofumigation Properties for the Suppression of Plant-Parasitic Nematodes: A Review

“…This aspect, along with a variety that has a high GSL content and with enough water present for hydrolysis to take place, ensure optimum biofumigation (Brown et al, 1991;Poulton & Moller, 1993;Morra & Kirkegaard, 2002;Matthiessen et al, 2004). One way to ensure the effective release of ITC is to slash the leaves with a slasher and then to plough the slashed residues into the soil as soon as possible, using a rotavator or disc harrow (Fig.…”