Plant & Animal Genomes XI Conference

January 11-15, 2003
Town & Country Convention Center
San Diego, CA

Workshop: Brassicas
            

DETECTION OF DE NOVO AND SEGREGATING CHROMOSOME REARRANGEMENTS IN FOUR MAPPING POPULATIONS OF BRASSICA NAPUS L.

Department of Agronomy, University of Wisconsin, 1575 Linden Dr., Madison, WI, 53705

An RFLP consensus linkage map was constructed from four Brassica napus double haploid (DH) mapping populations each sharing a common male parent. A resynthesized B. napus line derived from a cross of its diploid progenitors, B. rapa and B. oleracea, was used as the female parent of one of the DH populations (SYN). Chromosome rearrangements were identified in each DH population and were classified as either de novo non-reciprocal translocations (NRTs), segregating NRTs, or segregating reciprocal translocations (RTs). Fifty de novo NRTs were identified by the presence of in one or a few lines having duplication of homologous region and loss of the corresponding homoeologous region. These likely resulted from recombination between homoeologous chromosomes, and were most prevalent in the SYN population. Segregating NRTs were identified by the presence of many DH lines having duplications / losses due to segregation of NRT pre-existing in one of the parents. Seven pre-existing NRTs were identified in three of the four natural B. napus parents which probably originated from previous homoeologous exchanges The common male parent had a RT between N7 and N16 which segregated in the four DH populations. Thus, chromosome rearrangements may occur frequently in B. napus, and may impact recombination, and allelic, and phenotypic diversity. The evolution of B. napus, as a segmental allopolyploid will be discussed.