Construction of a F 1 DH population and high-density genetic map of ornamental kale

Abstract

Background Ornamental kale (Brassica oleracea var. acephala) is an attractive ornamental plant with a range of leaf colors and shapes. Owing to the long breeding cycle and limited availability of genetic markers, the breeding of new varieties of ornamental kale by traditional and marker-assisted selection (MAS) breeding methods is difficult. Microspore culture is an effective approach to generate new materials and a doubled-haploid (DH) population, which is suitable for genetic map construction. Genetic maps are a prerequisite for quantitative trait loci analysis, MAS, fine gene mapping, and genome sequence assembly. Here, we report the construction of a F1-derived doubled haploid (F1DH) population and high-density genetic map for ornamental kale to provide novel resources to use in breeding new varieties.Results A F1DH ornamental kale population comprising 300 DH lines, derived from parents that differed markedly in leaf shape and color, was constructed using microspore culture. More than 1000 regenerated plants were obtained, showing that the F1 progeny possessed high regeneration capacity, and the proportion of spontaneous chromosome doubling was higher than 50%. The F1DH population contained rich phenotypic diversity, especially variation in leaf color and shape. A high-density genetic map was generated by whole-genome resequencing using 150 F1DH individuals selected from the F1DH population. The genetic map contained 1696 bin-markers with 982,642 single-nucleotide polymorphisms (SNPs) spanning a total distance of 775.81 cM on all nine chromosomes with an average distance between markers of 0.46 cM. The ornamental kale genetic map contained substantially more SNP markers compared with published genetic maps for other B. oleracea crops. The haplotype and heat maps as well as the collinearity of the genetic and physical maps illustrated that the genetic map for ornamental kale was accurate and of high quality.Conclusions The F1DH progenies provide an excellent resource for germplasm innovation and breeding new varieties of ornamental kale. The high-density genetic map provides useful information for gene mapping and elucidation of the molecular mechanism of important agronomic traits of ornamental kale, and will aid in pseudochromosome assembly in genomic research on B. oleracea.