High UV-tolerance with introgression hybrid formation of Bupleurum scorzonerifolium Willd

The protoplasts of Arabidopsis thaliana (L.) Heynh. treated with 7.5 mM of IOA (iodoacetoamide) were fused with those of Bupleurum scorzonerifolium Willd, using PEG-mediated method. The protoplasts of B. scorzonerifolium were irradiated with ultraviolet light (UV) at an intensity of 380 μW/cm2 for 30, 60, 90, and 120 s, respectively, before fusion. In cell clones produced in all the fusion combinations, only those from Combination VI (UV 120 s) differentiated to plantlets. The cell lines and plantlets were identified as somatic hybrids by analysis of chromosome size and number, RAPD, 5S rDNA spacer sequence respectively. Genomic in situ hybridization (GISH) revealed that there was a complete set of chromosomes of donor (B. scorzonerifolium) in all hybrids with a few intact chromosomes and chromosome segment(s) of recipient (A. thaliana) in the hybrid cell lines from Combinations I-V or only chromosomal segment(s) in the regenerated cell lines from Combination VI. The numbers of chromosomal fragments from A. thaliana translocated or inserted to donor chromosomes increased with UV dose enhanced. The UV-tolerance of B. scorzonerifolium and indirect effect of UV on the exclusion and introgression of receptor (A. thaliana) chromosomes in the hybrid cells was discussed.