IMPROVING LEVELS OF BIOACTIVE COMPOUNDS IN BRASSICA VEGETABLES BY CROP MANAGEMENT STRATEGIES

Abstract

The Brassica family is a rich source of health-promoting compounds such as glucosinolates, carotenoids and chlorophylls. To date, little is known about the factors influencing the biosynthesis or degradation of phytochemicals at the pre-harvest stage. Therefore, we have studied the effects of genotype, ecophysiological factors, nutrition supply as well as elicitor and amino acid application on phytochemical content. At the genotypical level, different Asian Brassica species could be differentiated by their different compositions and contents of glucosinolates, carotenoids and chlorophylls. Additionally, a daily radiation sum >10 mol m -2 d -1 along with a daily mean temperature of <13°C increased lutein and alkyl glucosinolate contents in the broccoli heads, whereas the indole glucosinolate glucobrassicin was reduced. Furthermore, a higher mineral N supply resulted in a 30% reduction of the alkyl glucosinolates glucoraphanin and glucoiberin. Also, an increase in glucosinolate content induced by the addition of S was mainly because of increases in the alkyl glucosinolate glucoraphanin rather than to the indole glucosinolates; a phenomenon most likely due to the different biosynthetic pathways of alk(en)yl glucosinolates compared with indole glucosinolates. Leafstalk infusion of methionine, a precursor of alk(en)yl glucosinolate syntheses, also led to increased glucoraphanin and glucoiberin content in the broccoli head. Additionally, in turnip, elicitors such as salicylic acid and methyl jasmonate enhanced the aromatic glucosinolate gluconasturtiin and the indole glucosinolates in exudates. Taken together, the data provided here have implications for customer-oriented quality production and crop management strategies aiming to optimize health-promoting substance content in Brassicaceae.