Sequence-characterized amplified region and simple sequence repeat markers for identifying the major quantitative trait locus responsible for seedling resistance to downy mildew in Chinese cabbage (Brassica rapa ssp pekinensis)

摘要

Downy mildew caused by the oomycete Hyaloperonospora parasitica Constant. (Pers. Ex Fr.) is a serious threat to Brassicaceae family. Previously, a major quantitative trait locus (QTL) for seedling resistance (BrDW) and its flanking markers, K14-1030 and phosphoglucomutase, were identified in the Chinese cabbage. In order to establish the markerassisted selection (MAS) technique, K14-1030 was successfully converted into a sequence-characterized amplified region marker SCK14-825, and a bacterial artificial chromosome (BAC) with sequence homology to K14-1030 was identified. On the basis of the homologous and the linked BAC sequences, two microsatellite simple sequence repeat markers, kbrb058m10-1 and kbrb006c05-2, were designed and mapped on the confidence intervals of BrDW. These three markers could explain the QTL effect to a considerable extent and yield relatively high selection accuracy, which would be helpful in MAS for breeding downy mildew-resistant Brassica rapa ssp. pekinensis varieties.