Selenium affects the S-alk(en)yl cysteine sulfoxides among short-day onion cultivars

Four cultivars of onion (Allium cepa L. 'Primavera', 'Granex 33', 'Pegasus', and 'Sweet Success') were grown to maturity in modified nutrient solutions with or without 2.0 mg . L-1 Na(2)eO(4) (1.51 mg . L-1 SeO4-2). Selenium did not affect total flavor precursor content (ACSO) in 'Granex 33','Pegasus', and 'Sweet Success'. However, Se affected several individual ACSOs and precursor intermediates. Selenium decreased gamma-L-gtutamyl-S-(1-propenyl)-L-cysteine sulfoxide and trans(+)-S-(1-propenyl)-L-cysteine sulfoxide content in all four cultivars. (+)-S-Methyl-L-cysteine sulfoxide content was higher while (+)-S-propyl-L-cysteine sulfoxide content was lower with the added Se for two cultivars. Selenium lowered total bulb S content in all cultivars, and increased the percentage of total S accumulated as SO4-2 in three cultivars. The effect of Se on the flavor pathway was similar to that found when onions were grown under low S-concentrations. Flavor changes can be expected when onions are grown in a high Se environment, however, specific changes may be cultivar dependent.