Relationship of climate and genotype to seasonal variation in the glucosinolate–myrosinase system. II. Myrosinase activity in ten cultivars of Brassica oleracea grown in fall and spring seasons

Abstract Myrosinase catalyzes the hydrolysis of glucosinolates found in the Brassicaceae, generating a variety of bioactive reaction products that may aid in the prevention of some cancers and that are suppressive to soil‐borne plant pathogens. 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 if myrosinase activity varied by season. Regression models that included mean temperature and photosynthetic photon flux (PPF) during the growing seasons showed that climatic variables explained seasonal differences for myrosinase activity. Activity‐FW (FW = fresh weight; U g −1 ) and specific activity (U mg −1 ) were significantly ( p ≤ 0.05) affected by season, botanical group and group × season. Activity‐FW had a negative linear relationship with temperature, and a positive linear but negative quadratic relationship with PPF. Specific activity had a positive linear and a negative quadratic relationship with both temperature and PPF. Therefore the influence of climatic factors on myrosinase activity in Brassica species may affect the potential benefits of the glucosinolate–myrosinase system. Copyright © 2004 Society of Chemical Industry