Towards utilization of aneuploidy breeding in developing new types of diploids in brassica crops

The different species of Brassica crops originated from an urgenome of n=6 which differentiated into B genome(n=8), C genome (n=9) and A genome(n=10) by aneuploidization. In order to develop aneuploidy breeding in Brassica, the different phenomena involved in primary speciation by aneuploidization such as the formation of sesquidiploids, synthesis of aneuploids, euploidization and stabilization of the progenies were analyzed. Brassica campestris(2n=20, AA) was crossed with B. oleracea(2n=18, CC) and an artificial B. napus(2n=38, AACC) was produced. This was followed by backcrossing with B. campestris resulting in the synthesis of sesquidiploids(2n=29, AAC) which was further backcrossed to produce aneuploids with 2n=21, 22 etc. The sesquidiploids were characterized in terms of pollen fertility, seed set percentage in backcrossing and frequency distribution of chromosome number in the progenies. Similarly, the aneuploids which contained one or more additional chromosomes of B. oleracea were also analyzed cytologically and morphologically. After selfing and/or sibcrossing of the aneuploids, several types of diploids such as 2n=22 disomic addition lines as well as 2n=24, 26, 40 etc, were eventually synthesized. Upon stabilization, this may lead to the development of new types of diploids traits and establish aneuploidy breeding as an alternative approach in plant improvement programs.