Stabilization of new types of diploids (2n=22, 24) through selfing of aneuploids (2n=21, 22) derived from crossing of sesquidiploids (2n=29, AAC) and Brassica campestris (2n=20 AA)

Summary Aneuploids with 2n=21 and 2n=22 derived from crossing of sesquidiploids (2n=29, AAC) and Brassica campestris (2n=20, AA) were selfed successively in order to follow the changes in chromosome number of the progenies for three consecutive generations. Progenies with 2n=22, 23 and 24 obtained after selfing of S₀ generation and the succeeding S₁, S₂ and S₃ generations were analyzed in terms of pollen stainability, % seed set as well as cytogenetically based on meiotic behaviour with the aim of determining the possibility of addition of one or more alien chromosomes into n=10 species which may lead to differentiation of single or plural disomic addition lines. The generation of aneuploids with 2n=21 progressed in such a way that most plants seem to revert to the 2n=20 chromosome number of B. campestris after selfing. From 2n=22 aneuploids, however, the succeeding progenies showed high frequency of plants with two additional chromosomes which accounted for 50.6% and 52.9% of total S₃ progenies via 2n=22 and 2n=24 S₂ generations, respectively. The meiotic behaviour of these progenies indicated evidence for a rule governing the frequency distribution of chromosome number among these addition lines and high possibility to breed such disomic plants with 2n=22. A method of selecting stable aneuploids was suggested in addition to the possible role of pollination biology at various processes of such breeding program.