MITOTIC KARYOTYPES OF BRASSICA-CAMPESTRIS AND BRASSICA-ALBOGLABRA ANDIDENTIFICATION OF THE B-ALBOGLABRA CHROMOSOME IN AN ADDITION LINE

A Brassica campestris-alboglabra monosomic addition line (genome: AA one chromosome from the C genome, 2n = 21) harbours the Brassica albo glabra (CC, 2n = 18) chromosome with the gene for erucic acid. In orde r to identify this chromosome, we have studied the mitotic prometaphas e chromosomes of Brassica campestris (AA, 2n = 20), B. alboglabra, and the monosomic addition line. More pronounced differential staining an d size differences of chromosomes were observed in B. campestris than in B. alboglabra. The karyotype of B. campestris was composed of four median (m), four submedian (sm), and two subterminal (st) chromosome p airs, while that of B. alboglabra was composed of three m, four sm, an d two st chromosome pairs, provided that the length of the satellite w as excluded when determining the arm ratio of the nucleolar chromosome . The alien chromosome from the C genome in the addition line was easi ly identified in the background B. campestris genome by its large size , its submedian centromere, and its differential staining pattern. Whe n compared with the karyotype of B. alboglabra, the alien chromosome f rom the C genome in the monosomic addition line was revealed to be chr omosome 4.