Relationship of climate and genotype to seasonal variation in the glucosinolate-myrosinase system.: I.: Glucosinolate content in ten cultivars of Brassica oleracea grown in fall and spring seasons

Two cultivars each of broccoli (Brassica oleracea L var italica), Brussels sprouts (B oleracea var gemmifera), cabbage (B oleracea var capitata), cauliflower (B oleracea var botrytis) and kale (B oleracea var acephala) were grown during two fall seasons and two spring seasons to determine whether significant seasonal effects on glucosinolate (GS) concentrations could be explained by mean temperature, photosynthetic photon flux (PPF) and daylength during the growing seasons. Concentrations of total GSs, indole GSs and glucoraphanin differed by genotype and season. Total GS concentrations at harvest had a negative linear but positive quadratic relationship with temperature and daylength over the 2 weeks preceding harvest and a positive linear but negative quadratic relationship with PPF over the same 2 weeks. The regression model for indole GS concentrations similarly varied with mean temperature, daylength and PPF over the 4 weeks prior to harvest. Glucoraphanin concentrations at harvest decreased linearly with mean PPF from transplanting to harvest and had a negative linear but positive quadratic relationship with daylength from transplanting to harvest. Because glucoraphanin and other GSs in cruciferous crops are important for cancer chemoprotection, climatic conditions should be considered when planning planting dates or when making breeding selections for GS concentration. (C) 2004 Society of Chemical Industry.