Mapping of Pi, a gene conferring pink leaf in ornamental kale (Brassica oleracea L. var. acephala DC)

We previously found that pink leaf is conferred by a single semi-dominant gene in ornamental kale. To map this gene, we constructed an F-2 segregating population containing 184 individuals by crossing W02-7, a white-leaved inbred line, with P02-9, a pink-leaved inbred line. We screened 297 simple sequence repeat (SSR) and 437 sequence-related amplified polymorphism (SRAP) markers using bulked segregant analysis. We identified one SSR and seven SRAP markers that linked tightly to the pink-leaf (Pi) gene. To obtain more specific genomic markers, we converted six SRAPs to sequence-characterized amplified region (SCAR) markers. We constructed a genetic linkage map of the Pi locus using one SSR and five SCAR markers, spanning a total interval of 15.0 cM. One SSR marker, Ni2C12, and one co-dominant SCAR marker, Boac04, flanked Pi on either side at distances of 0.6 and 2.4 cM, respectively. Based on the reference genome sequence of Brassica oleracea, we positioned Pi on the top of chromosome C3. We also detected that pink hypocotyl co-segregated with pink inner leaf. These markers provide the basis for fine-scale mapping and cloning of Pi, and may be used for marker-assisted selection in ornamental kale breeding programs.