Genetic diversification of allohexaploid Brassica hybrids (AABBCC) using fertile octoploid with excessive C genome set

Abstract Even if somatic hybrids are produced, they are usually the end products and are difficult to develop as an innovative crop. In this study, we used somatic hybrids of Brassica juncea (AABB) and B. oleracea (CC) as model cases for the genetic diversification of the somatic hybrids. One cell of ‘Takana’ (B. juncea) and two cells of ‘Snow Crown’ (B. oleracea) were fused to create several somatic hybrids with excessive C genomes, AABBCCCC. Using AABBCCCC somatic hybrids as mother plants and crossbreeding with ‘Takana’, the AABBCC progenies were generated. When these AABBCC progenies were self-fertilized, and flow cytometric analysis was performed on the next generations, differences in the relative amount of genome size variation were observed, depending on the different individuals of AABBCCCC. In other words, somatic hybrid generations may be involved in the genetic stability/instability of generations produced by crossbreeding. Next, to obtain genetic diversification of the trigenomic hexaploid, different cultivars of B. juncea were crossed with AABBCCCC, resulting in a series of later generations with diverse AABBCC genomes. Genetic diversity can be further expanded by crossbreeding plants with different AABBCC genome sets. Although genetic stability is necessary to ensure in the later generations, the results obtained in this study show that the use of somatic hybrids with excess genomes is an effective strategy for creating innovative crops.