A high-density genetic map and QTL mapping of leaf traits and glucosinolates in Barbarea vulgaris.

Background: Barbarea vulgaris is a wild cruciferous plant and include two distinct types: the G- and P-types named after their glabrous and pubescent leaves, respectively. The types differ significantly in resistance to a range of insects and diseases as well as glucosinolates and other chemical defenses. A high-density linkage map was needed for further progress to be made in the molecular research of this plant.

Results: We performed restriction site-associated DNA sequencing (RAD-Seq) on an F population generated from G- and P-type B. vulgaris. A total of 1545 SNP markers were mapped and ordered in eight linkage groups, which represents the highest density linkage map to date for the crucifer tribe Cardamineae. A total of 722 previously published genome contigs (50.2 Mb, 30% of the total length) can be anchored to this high density genetic map, an improvement compared to a previously published map (431 anchored contigs, 38.7 Mb, 23% of the assembly genome). Most of these (572 contigs, 31.2 Mb) were newly anchored to the map, representing a significant improvement. On the basis of the present high-density genetic map, 37 QTL were detected for eleven traits, each QTL explaining 2.9-71.3% of the phenotype variation. QTL of glucosinolates, leaf size and color traits were in most cases overlapping, possibly implying a functional connection.

Conclusions: This high-density linkage map and the QTL obtained in this study will be useful for further understanding of the genetic of the B. vulgaris and molecular basis of these traits, many of which are shared in the related crop watercress.