UV dose-dependent DNA elimination in asymmetric somatic hybrids between Brassica napus and Arabidopsis thaliana

To evaluate W-irradiation as an alternative method for chromosome fragmentation in the production of asymmetric somatic hybrids, UV-irradiated protoplasts of Arabidopsis thaliana were fused with protoplasts of Brassica napus. The A. thaliana protoplasts were irradiated with doses between 780 and 28 080 J/m(2) (lambda = 254 nm) and hybrid plants were obtained from experiments using doses of 780, 2340 and 4680 J/m(2). In addition, a control fusion experiment without irradiation was performed. In total, 312 shoots were regenerated and of those 58 plants were analysed for presence of A. thaliana DNA, using 13 mapped A. thaliana RFLP markers (two to four per chromosome). Increased W-irradiation dose resulted in a higher frequency of asymmetric hybrids and a higher dose was also associated with the generation of hybrids with a higher degree of asymmetry. RFLP data further indicated that irradiation primarily resulted in loss of chromosome fragments rather than whole chromosomes from A. thaliana. Fertility was studied in 119 hybrid plants by selfing as well as pollination by B. napus. The fertility after selfing increased with increasing W-irradiation dose, while the results of back-crossing were not affected by the irradiation. (C) 1998 Elsevier Science Ireland Ltd.