Mapping the Anthocyaninless (anl) Locus in Rapid-Cycling Brassica rapa (RBr) to Linkage Group R9

<p>Abstract</p> <p>Background</p> <p>Anthocyanins are flavonoid pigments that are responsible for purple coloration in the stems and leaves of a variety of plant species. <it>Anthocyaninless </it>(<it>anl</it>) mutants of <it>Brassica rapa </it>fail to produce anthocyanin pigments. In rapid-cycling <it>Brassica rapa</it>, also known as Wisconsin Fast Plants, the anthocyaninless trait, also called non-purple stem, is widely used as a model recessive trait for teaching genetics. Although anthocyanin genes have been mapped in other plants such as <it>Arabidopsis thaliana</it>, the <it>anl </it>locus has not been mapped in any <it>Brassica </it>species.</p> <p>Results</p> <p>We tested primer pairs known to amplify microsatellites in <it>Brassicas </it>and identified 37 that amplified a product in rapid-cycling <it>Brassica rapa</it>. We then developed three-generation pedigrees to assess linkage between the microsatellite markers and <it>anl</it>. 22 of the markers that we tested were polymorphic in our crosses. Based on 177 F₂offspring, we identified three markers linked to <it>anl </it>with LOD scores ≥ 5.0, forming a linkage group spanning 46.9 cM. Because one of these markers has been assigned to a known <it>B. rapa </it>linkage group, we can now assign the <it>anl </it>locus to <it>B. rapa </it>linkage group R9.</p> <p>Conclusion</p> <p>This study is the first to identify the chromosomal location of an anthocyanin pigment gene among the <it>Brassicas</it>. It also connects a classical mutant frequently used in genetics education with molecular markers and a known chromosomal location.</p

A new broccoli × broccoli immortal mapping population and framework genetic map: tools for breeders and complex trait analysis

A unique broccoli x broccoli doubled haploid (DH) population has been created from the F-1 of a cross between two DH broccoli lines derived from cultivars Green Duke and Marathon. We genotyped 154 individuals from this population with simple sequence repeat and amplified fragment length polymorphism markers to create a B. oleracea L. var. italica 'intra-crop' specific framework linkage map. The map is composed of nine linkage groups with a total length of 946.7 cM. Previous published B. oleracea maps have been constructed using diverse crosses between morphotypes of B. oleracea; this map therefore represents a useful breeding resource for the dissection of broccoli specific traits. Phenotype data have been collected from the population over five growing seasons; the framework linkage map has been used to locate quantitative trait loci for agronomically important broccoli traits including head weight (saleable yield), head diameter, stalk diameter, weight loss and relative weight loss during storage, as well as traits for broccoli leaf architecture. This population and associated linkage map will aid breeders to directly map agronomically important traits for the improvement of elite broccoli cultivars