First genetic linkage map for comparative mapping and QTL screening of brill (Scophthalmus rhombus)

Genetic maps constitute valuable tools to detect genomic regions associated with complex traits and to go forward to understand their genetic basis. Flatfish include several species of great commercial value for which increasing genomic resources are available including genetic maps and EST databases. Application of comparative mapping strategies to flatfish is relevant to obtain genetic information associated with productive traits. The brill (Scophthalmus rhombus) is a flatfish species closely related to turbot (S. maximus) whose meat is highly appreciated in the Spanish market. The Junta de Andalucía local Government has begun a program to adapt this species to captivity for its future production. In this study, we developed the first genetic map of brill using the current turbot genetic map as starting point. This strategy enabled us to select a number of homogeneously distributed markers in the turbot map and to apply cross-species microsatellite amplification to obtain informative markers. Nearly two hundred microsatellites from the framework turbot map were used for validation, and 100 markers were finally informative for mapping. The parents and offspring of the two families (54 and 88, respectively) used to construct the genetic map were genotyped with this panel. All markers, except eleven, were successfully grouped and ordered in 24 linkage groups. Linkage groups and order of markers were highly consistent with the previous turbot genetic map. Linkage map information was used to carry out a preliminary study on growth-related QTL for body weight, length and Fulton's condition factor in the two families, as the main phenotypic traits of interest in this species.