Linkage analysis among loci for RAPDs, isozymes and some agronomic traits in Brassica campestris L.

Abstract

F2 populations from a hybrid between an inbred line of Chinese cabbage (Brassica campestris L. var. pekinensis, 2n = 20) and an inbred line of Mizu-na (B. campestris L. var. japonica 2n = 20) were grown in two seasons, and were analyzed with RAPD and isozyme markers to construct a linkage map following our previous linkage analyses for 19 isozyme loci. A total of 52 RAPD markers were integrated into ten linkage groups, which is the same as the haploid chromosome number of B. campestris. Genes for morphological traits, such as leaf shape, period to bolting, leaf hairiness, the self-incompatibility (the S-glycoprotein) and the NS-glycoprotein which has a high degree of structural homology with the S-glycoprotein, were found to link to the RAPD markers by QTL or linkage analyses. Leaf shape was found to be controlled by multiple genes in two linkage groups. Leaf hairiness seemed to be controlled by a single gene and to be linked to a group of RAPD markers. The period to bolting was found to be controlled by at least two independent loci in the genome. A RAPD marker showing linkage to the self-incompatibility locus showed a recombination value of 20.2%. The NS-glycoprotein locus was linked to the ACP-1 isozyme locus. Linkages between markers and traits are useful for developing marker-assisted selection of important traits.