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 frag mentation in the production of asymmetric somatic hybrids, UV-irradiat ed 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 wer e obtained from experiments using doses of 780, 2340 and 4680 J/m(2). In addition, a control fusion experiment without irradiation was perfo rmed. In total, 312 shoots were regenerated and of those 58 plants wer e analysed for presence of A. thaliana DNA, using 13 mapped A. thalian a RFLP markers (two to four per chromosome). Increased W-irradiation d ose 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 prim arily resulted in loss of chromosome fragments rather than whole chrom osomes from A. thaliana. Fertility was studied in 119 hybrid plants by selfing as well as pollination by B. napus. The fertility after selfi ng increased with increasing W-irradiation dose, while the results of back-crossing were not affected by the irradiation. (C) 1998 Elsevier Science Ireland Ltd.