ABSTRACT
Brassica campestris-alboglabra monosomic addition lines were developed from a trigenomic Brassica hybrid (2 n=3 x=29, AAC) obtained by backcrossing a resynthesized B. napus (2 n=4 x=38, AACC) line to its parental B. campestris (2 n=2 x=20, AA) line. One addition line was characterized genetically with three loci specific for the alien chromosome and cytologically by meiotic analysis. The following results were obtained. (1) The same chromosome in the B. alboglabra (2 n= 2 x=18, CC) genome carried the three loci, E c, W c and Lap-1 C (c), which control the biosynthesis of erucic acid, white flower colour and the faster migrating band of leucine aminopeptidase, respectively. The linear order and possible positions of the three loci were inferred. The meiotic behaviour of the alien chromosome was documented and its transmission frequency was assessed. (2) Intergenomic recombination frequently occurred in the monosomic addition line, resulting in the introgression of one or two loci from the alien chromosome into the B. campestris genome. (3) B. campestris trisomics were found in the progeny of the monosomic addition line. (4) The removal of the other eight C-genome chromosomes from the trigenomic Brassica hybrid led to a dramatic increase in the erucic acid content of the monosomic addition line. (5) No offspring of the trigenomic Brassica hybrid showed evidence of intergenomic recombination and introgression of the W c locus into the B. campestris genome. It is questioned whether such a difference might be due to a possible regulating mechanism for homoeologous chromosome pairing.
