LAUSR

Interspecific hybrids between related species have long been used for transferring desirable genes, broadening genetic diversity and utilizing intersubgenomic heterosis. In this study, we developed a novel Brassica rapa type (AA, 2n = 20) exhibiting certain features derived from interspecific hybridization between natural B. rapa and Brassica juncea (AABB, 2n = 36). In pollen mother cells (PMCs) of the novel B. rapa type, normal chromosome pairing with 10 bivalents and 10:10 segregation was observed, and the novel B. rapa lines were completely fertile. However, GISH showed that certain B chromosomes or fragments were introgressed into B. rapa. Genetic components of the novel B. rapa lines were investigated by GISH, AFLP and SSR analyses. GISH analysis of F1, BC1F1, and BC1F2 plants confirmed the identities of three addition lines and seven translocation lines. AFLP and SSR analyses of 60 hybrid progenies from BC1F4 plants, their parents, and some B. juncea and B. rapa resources indicated that the AJ and B chromosome(s) or fragment(s) introgressed to the novel B. rapa. AFLP revealed that 60 BC1F4 plants contained B chromosomes or fragments, which evidenced introgression into the hybrid progeny. SSR analysis indicated that the A-genome (A1–A10) of B. juncea was introgressed into the hybrid progeny at 1.0 to 42.7%. Lastly, we obtained some yellow-seed and early-flowering B. rapa resources. The novel B. rapa lines can be used to genetically improve B. rapa in the Qinghai-Tibet Plateau and to study the origin and evolution of the A- and B-genomes.