Genetic characteristics of aneuploids derived from interspecific crosses of Brassica campestris and B. oleracea

The potential of aneuploidy breeding for improvement of Brassica crops was analyzed. B. campestris was crossed with B. oleracea producing artificial B. napus and this was followed by backcrossing with B. campestris ssp. pekinensis and chinensis to produce new type of amphidiploids. The morphological characteristics, fertility and chromosome number of the sesquidiploids as well as the hypo-aneuploids were described in detail. The sesquidiploids showed a wide range of pollen fertility from 0.0% to 60.4% and individuals with high percent seed set were obtained from those with pollen fertility above 40%. A total number of 185 plants from the backcross between the sesquidiploids and B. campestris showed 20.6% progenies with 22 chromosomes and 21.4% with 23 chromosomes. This may be due to binomial distribution of chromosome number at metaphase Ⅱ commonly found in sesquidiploids. The fertility of derived aneuploids showed that with increasing chromosome number there was a tendency of decreasing pollen fertility as well as percent seed set. Morphological characteristics of hypo-aneuploids showed the possibility that one to nine chromosomes of the C genome was added to the chromosome complement of B. campestris based on such characteristics as waxy leaves, distinct midrib, petiole, leaf shape, leaf color and flowering date. Six types of aneuploids were classified and suggested that a single B. oleracea chromosome was incorporated in the progenies. Thus, aneuploidy breeding can be a promising approach in developing new types of amphidiploids in Brassica crops.