Phenotypic and genetic variation occurred during wide hybridisation and allopolyploidisation between Brassica rapa and Brassica nigra

Abstract

Wide reciprocal hybridisations between Brassica rapa (genome: AA) and Brassica nigra (genome: BB) were performed in the present study. The results indicate that use of B. rapa as female parent and B. nigra as male parent was appropriate for wide hybrid production, and allotetraploids and alloaneuploids could be induced by treating allodiploids with 0.2% colchicine for 16h and 24h. When allodiploids, T-allodiploids (allodiploids after treating with colchicine), allotetraploids and alloaneuploids were transferred to the field, the allotetraploids exhibited more vigorous growth compared to the allodiploids and T-allodiploids. Compared with their parents, the allotetraploids displayed 21.07% polymorphic fragments measured by the sequence related amplified polymorphism (SRAP) analysis, which was the double compared to the allodiploids. Moreover, the novel fragments in allotetraploids were more than twice the number of that in allodiploids. The novel fragments matched homologous functional genes when blasted against genome databases. When the allotetraploids (F1) were self-crossed, the next generation (F2) exhibited the same phenotype and genetic pattern. These results indicated that the degree of genetic changes were positively related with the polyploidy level during the process of heterogeneous chromosomes combinations and chromosome doubling, and both wide hybridisation and genome doubling could affect the genomic architecture in newly formed allopolyploids. Moreover, novel fragments may be correlated with novel phenotypes.