High glucosinolate broccoli: a delivery system for sulforaphane

Abstract

The development of hybrid broccoli genotypes with enhanced levels of 4-methylsulphinylbutyl glucosinolate, the precursor of anticarcinogenic isothiocyanate sulforaphane (SF), by introgressing genomic segments from the wild ancestor Brassica villosa is described. We demonstrate that to obtain enhanced levels of either 3-methylsulphinylpropyl or 4-methylsulphinylbutyl glucosinolate it is necessary to have B. villosa alleles in either a homozygous or heterozygous state at a single quantitative trait locus (QTL) on O2. The ratio of these two glucosinolates, and thus whether iberin or SF is generated upon hydrolysis, is determined by the presence or absence of B. villosa alleles at this QTL, but also at an additional QTL2 on O5. We further demonstrate that following mild cooking high glucosinolate broccoli lines generate about three fold higher levels of SF than conventional varieties. Commercial freezing processes and storage of high glucosinolate broccoli maintains the high level of glucosinolates compared to standard cultivars, although the blanching process denatures the endogenous myrosinase activity.