A microsatellite (SSR) based linkage map of Brassica rapa

In the present study we describe the construction of a genetic linkage map for the Brassica rapa (AA) genome that will act as a key resource in undertaking future structural and functional genomic studies in B. rapa. A F(2) mapping population consisting of 48 F(2) individual plants developed following hybridization of 2 inbred lines Bathari mandi and IC 331817 was used to construct the map. The map comprises 53 SSR markers derived from 3 different public domain resources. Nine linkage groups along with a small subgroup were identified and designated as R(1)-R(9) through alignment and orientation using SSR markers in common with existing B. rapa reference linkage maps. The total length of the genetic linkage map was 354.6 cm with an average interval of 6.6 cm between adjacent loci. The length of linkage groups ranged from 28.0 cm to 44.2 cm for R(6) and R(1A), respectively. The number variability of markers in the 9 linkage groups ranged from 3 for R(6) to 10 for R(1). Of the 53 SSR markers assigned to the linkage groups, only 5 (9.4%) showed deviation from the expected segregation ratio. The development of this map is vital to the genome integration and genetic information and will enable the international research community to share resources and data for the improvement of B. rapa and other cultivated Brassica species.