The myrosinase-glucosinolate system as a source of bioactive molecules for controlling postharvest diseases

The strong demands of public opinion to reduce the use of conventional fungicide and the phase-out of several of these compounds have spurred the research to look for more healthy and environmental friendly practices to control postharvest fruit pathogens. Among these, the biofumigation with isothiocyanates (ITCs) produced by the glucosinolate-myrosinase system contained in Brassica plants was the most promising. In fact, ITCs have proved to be effective in controlling Penicillium expansum and Monilinia laxa and others important fruit pathogens during postharvest phase both in vitro and in vivo tests (1, 2). In addition, it has been demonstrated that some ITCs are able to control even P. expansum resistant strains to thiabendazole, which is the most common fungicide used for controlling postharvest green blue mould. In particular, allyl isothiocyanate (AITC) obtained from sinigrin via myrosinase-catalyzed reaction, appears to be the most suitable compound to be used in biofumigation due to its volatility and high biological activity. AITC is a component of the mustard oil that is recognized as safe compound (GRAS Notice N° GRN 000180) by the Food and Drug Administration (FDA). On the basis of these considerations, a number of trials using a pre-pilot plant built up for carrying out large scale biofumigation before storage trials (3) to control M. laxa and P. expansum on stone fruits and on pears respectively have been carried out. The most positive results were obtained using AITC produced in situ from wetted defatted meals of Brassica carinata. After treatment, fruits were stored at low temperature under standard conditions for a variable time depending on the fruit type. Peach and nectarine were naturally infected, whereas pears were inoculated 24 hours before treatment. A summary of the most interesting results and the technical hitches emerged applying this procedure are presented and discussed.