Autoplasmic and alloplasmic Brassica napus with a single chromosome of B-genome (MAL, 2n=39) were bred from progenies of the reciprocal interspecific F₁ hybrids between B. napus (AACC) and Brassica juncea (AABB) with backcrossing to B. napus. The alien chromosomes of the B-genome (n=8, a–h) of B. juncea were identified by B-genome specific microsatellite markers, cytogenetic observation and morphological characteristics. As a results, there were six types in autoplasmic MALs, except for the a-type and the f-type, the alloplasmic ones were also identified to six types, except for the e-type and the f-type. A total of seven types of MAL showed predominantly the chromosome configuration of 19_II+1_I in metaphase I but a few multivalent chromosomes were also observed. The morphological traits suggested that the external form was affected by the additional g and h chromosomes. The transmission rates of MALs varied from 1.9% to 36.4%, indicating that each added B-genome chromosome could be inherited to the next generation. Traits of each B-genome chromosomes determined by studying MALs will facilitate the study of transductions and homoeologous relationships in Brassica genera.

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