Natural Variation of Glucosinolates and Their Breakdown Products in Broccoli (Brassica oleracea var. italica) Seeds.

Seeds of 32 pure lines and six commercial broccoli cultivars were used to investigate variation in glucosinolates and their breakdown products. Aliphatic glucosinolate content was 54.5-218.7 μmol/g fresh weight, accounting for > 90 % of the total glucosinolates. The major glucosinolates found were glucoraphanin and glucoerucin in 27 samples, and progoitrin in 7 samples. A gas chromatography-flame ionization detector (GC-FID) method was used to identify glucosinolate breakdown products; nine products were directly determined using standards. Using Arabidopsis thaliana lines myb28myb29 and Landsberg erect to hydrolyze each reference glucosinolate, seven products were tentatively identified. 4-(Methylsulfinyl)butyl isothiocyanate and 5-(methylsulfinyl)pentanenitrile contents were 2.6-91.1 μmol/g fresh weight and 0-35.4 μmol/g fresh weight, respectively, with epithionitriles being more common than nitriles in accessions rich in alkenyl glucosinolate. Additionally, (S)-5-vinyl-1,3-oxazolidine-2-thione was detected in accessions rich in progoitrin. Specific lines with altered glucosinolate profiles and breakdown products were obtained and discussed according to the putative glucosinolate metabolism pathway.