Mapping the BrPur gene for purple leaf color on linkage group A03 of Brassica rapa

The purple-leaf phenotype in Chinese cabbage is due to the accumulation of anthocyanin. To investigate the pattern of inheritance of this trait in Brassica rapa, F-1, F-2 and backcross (BC) populations were constructed by crossing 09N-742, a pak-choi inbred line that has purple leaves, with a green-leaved Chinese cabbage inbred line, 09-680. Using a segregating F-2 population, we identified a single dominant gene, BrPur, for purple leaf, and mapped the gene to a locus on linkage group A03 of B. rapa. Furthermore, sequences from BAC clones and other sources were used to develop molecular marker loci that are tightly linked to BrPur by using a BC1 population of 1,152 individuals. BrPur was assigned to a locus between Indel markers BVRCPI613 and BVRCPI431, which defined a genetic interval of 0.6 cM and a genomic region of 54.87 kb. Sequence analysis of this chromosomal region revealed seven open reading frames. These results provide a foundation for map-based cloning, identification, and functional analysis of the BrPur gene in B. rapa.