The Effect of Water Stress on the Glucosinolate Content and Profile: A Comparative Study on Roots and Leaves of Brassica oleracea L. Crops

Drought is one of the major challenges of global crop production, and its severity is
increasing because of climate change. This abiotic stress is an important target for Brassica species,
which are generally grown in arid and semi-arid climates. This study was conducted to investigate the
effects of water deficit on a set of accessions belonging to the Brassica core collection of the EU H2020
BRESOV project, represented by Brassica oleracea L. crops and Brassica oleracea complex species (n = 9).
In particular, the variation in the amount and profile of the glucosinolates (GLSs) compounds was
analyzed on the root and the leaf tissues. The plant morphometric traits and GLSs amount and profile
were detected for the plants grown in cold greenhouse in Catania (Sicily) during the autumn–winter
season for ten weeks. The results showed a wide qualitative and quantitative variation among the
Brassica accessions. The GLSs profile varied qualitatively and quantitively among both genotypes
and portions of the plants (hypogenous-root and epigeous-leaf). Plants grown under drought stress,
for the last two weeks of the growing cycle under consideration, showed a higher amount of GLS
in their leaves (190.1 ± 8.9 μmol·g−1 d.w.) compared to their roots (17.3 ± 1.9 μmol·g−1 d.w.). Under
water stress conditions, the highest increase in the glucosinolate amount was detected in broccoli (the
accession BR1) with 85.4% and in cauliflower (the accession CV1) with 72.8% in the roots and leaves,
respectively. Positive correlations were found between the major leaf and root GLSs identified. The
selection of chemotypes allows for an important time reduction during the breeding programs after
crossing accessions with the specific profiles of glucosinolates.