Sulphur fertilization may improve the nutritional value of Brassica rapa L. subsp. sylvestris

Sulphur is essential in the biosynthesis of secondary metabolites with high nutritional value that typically accumulate in brassica species. Among these, glucosinolates are the most representative. The level of glucosinolates in these plants is highly dependent on genetic factors as well as environmental determinants, such as the available soil sulphur content. There is an increasing need of defining the metabolic profile of brassica species in response to both cultivation practices and environmental factors since a targeted modification of its constituents may significantly affect the functional properties and the commercial value of these vegetables. Here, we report on the effects of sulphur fertilization on flavonols, phenolic acids and glucosinolates contents of two friariello (Brassica rapa L. subsp. sylvestris L. Janch. var. esculenta Hort.) ecotypes-Lingua di Cane and Sorrentino. Friariello quality in terms of sprouts plus inflorescence nitrate and chlorophyll contents was also assessed. We found a significantly higher flavonols content in the ecotype Sorrentino, whereas its glucosinolates level was relatively smaller compared to Lingua di Cane. Sulphur fertilization significantly improved the antioxidant activity of both ecotypes and was associated with a genotype-dependent significant reduction of leaf nitrate content.