Evaluation of Glucosinolate Variation in a Collection of Turnip (Brassica rapa) Germplasm by the Analysis of Intact and Desulfo Glucosinolates

Glucosinolates
(GLS) are secondary metabolites occurring in cruciferous
species. These compounds are important for plant defense, human health,
and the characteristic flavor of Brassica vegetables. In this study,
the GLS in tubers from a collection of 48 turnip (Brassica
rapa) accessions from different geographic origin
were analyzed. Two different methods were used: desulfo GLS were analyzed
by high-performance liquid chromatography with a photodiode array
detector, and intact GLS were analyzed by accurate mass liquid chromatography–mass
spectrometry. For most GLS, desulfo and intact signals correlated
well, and the analytical reproducibility for individual GLS was similar
for both methods. A total of 11 different GLS was monitored in the
turnip tubers, through both intact and desulfo GLS analysis methods.
Four clusters of accessions could be clearly distinguished based on
GLS composition of the turnip tuber. Clustering based on tuber GLS
differed markedly from a previously published clustering based on
leaf GLS.