Dissection of quantitative traits in oilseed rape for marker development using Brassica-Arabidopsis comparative genomics

摘要

The growing resource of Brassica genome sequence data, along with the ever-improving annotation of Brassica sequences to the extremely well-characterised genome of the model crucifer Arabidopsis thaliana, represent an extremely valuable resource for molecular breeding and genetic characterisation of B. napus. In particular, the newest comparative genomics data enable a unique opportunity to navigate between and among the chromosomes of A. thaliana and B. napus, and to compare the map positions of quantitative trait loci (QTL) for complex traits of agronomic importance in the crop species with the positions of potential candidate genes in the model genome. In some cases such rough macrosynteny enables the detection of chromosome blocks in rapeseed corresponding to more or less unbroken syntenic genome regions in Arabidopsis. On the one hand this can allow orthologous Brassica sequences annotated to the corresponding Arabidopsis regions to be used for datahase-oriented identification of new markers for fine mapping, association studies or marker-assisted selection towards trait improvement. In some cases it is also possible to directly identify potentially relevant candidate genes for important traits in oilseed rape, based on their position in syntenic maps compared to relevant QTL. In other cases it can be feasible to navigate from potential candidate genes in Arabidopsis to homoeologous regions of the rapeseed genome, whereby not only the gene sequence itself but the complete surrounding region can be used to search for sequence polymorphisms that can be utilised as markers. In this paper we demonstrate the potential of comparative genomics data for candidate gene identification and marker development in traits related to oilseed rape seed quality. Different approaches are for dissection of traits that appear to be controlled by a relatively small number of major genes (e.g. seed colour and fibre content), and traits influenced by numerous homoeologous QTL containing an unknown number of active genes (e.g. glucosinolate content). In each case new information can be obtained that can lead to new,tightly-linked selection markers and the identification of new allelic diversity for breeding.