Introgression of Swertia mussotii gene into Bupleurum scorzonerifolium via somatic hybridization

Protoplasts derived from calli of Bupleurum scorzonerifolium and S. mussotii were fused to produce 194 putative hybrid cell lines, of which three (all derived from fusions where the S. mussotii protoplasts were pre-treated for 30 s with UV light) later differentiated into green plants. The hybridity of the calli was confirmed by a combination of isozyme, RAPD and chromosomal analysis. The hybrid calli genomes were predominantly B. scorzonerifolium. GISH analysis of mitotic chromosomes confirmed that the irradiation of donor protoplasts increased the frequency of chromosome elimination and fragmentation. RFLP analysis of organellar DNA revealed that mitochondrial and chloroplast DNA of both parents coexisted and recombined in some hybrid cell lines. Some of the hybrid calli contained SmG10H from donor, and produced swertiamarin, mangiferin and certain volatile compounds characteristic of S. mussotii. The expression of SmG10H (geraniol 10-hydroxylase) was associated with the heterologous accumulation of swertiamarin.Somatic hybrids between B. scorzonerifolium and S. mussotii were obtained, hybrids selected all contained introgressed nuclear and cytoplasmic DNA from S. mussotii; and some produced more mangiferin than the donor itself. The introgression of SmG10H was necessary for the accumulation of swertiamarin.Somatic hybridization provides a means to bypass the problem of sexual incompatibility which prevents the production of many wide hybrids in the plant kingdom. The technique has been successfully demonstrated in a number of intra- and inter-specific, intergeneric, intertribal and even inter-familial combinations [1-4]. The possibility of introgression from exotic sources is of interest not just in the applied field, but also because it provides opportunities for the discovery of novel synthetic pathways for secondary metabolites and signalling compounds.The medicinal herb Swertia mussotii Franch is native to Tibet, where it has enjoyed a long history of use as