Water deficit is regarded as one of the severe abiotic stresses, which harmfully affect productivity and plant growth. Brassica crops are essential providers of whole oilseed production; therefore, it is necessary to improve tolerant cultivars to guarantee yields under opposing conditions. In the present study, we tested 105 doubled haploid of Brassica oleracea under control and 17% of polyethylene glycol (PEG), as induced drought. A significant variation was observed among the genotypes under both control and drought for all studied traits. There was a considerable reduction in performance for seed germination and seedling-related traits under drought stress (17% compared to control conditions), except that root length, protein, and proline increased. Heritability was very high for all traits except protein and proline under both control and drought. It ranged from 27.51 to 99.98 under the control condition and from 26.65 to 99.98 under drought, respectively. Thirty-nine Quantitative trait loci (QTLs) are scattered across the nine chromosomes of Brassica. Several hotspots of QTLs were localized for different traits. Remarkably, some markers governed many traits in a pleiotropic manner; therefore, they are valuable for improving several traits at the same time. Some QTLs were nonspecific (constitutive), i.e., they are plotted under control and drought, and targeting these QTLs makes the selection for drought tolerance a single-step process. These results are of high importance for improving drought tolerance in Brassica, not only for this collection but for all Brassica species that includes the C genome such as (Brassica napus and Brassica carinata), as the parental line (TO1000DH3) is the reference genome for Brassica oleracea sequencing project.
Key words: Drought tolerance index, hotspot, Brassica, Quantitative trait loci
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