Comparison of UV light, X-ray and restriction enzyme treatment as tools in production of asymmetric somatic hybrids between Brassica napus and Arabidopsis thaliana

Asymmetric somatic hybrids between Brassica napus (receptor) and Arabidopsis thaliana (donor) have been produced by three different methods supposed to induce asymmetry. The donor protoplasts were either UV- or X-irradiated, or the mixture of protoplasts was treated with the restriction enzyme PvuII immediately before fusion. The genome composition of the hybrids was analysed with Southern blot hybridisations using 15 different mapped A. thaliana RFLP markers as probes. Both UV- and X-irradiation were found to be efficient treatments for induction of asymmetry in somatic hybrids in a dose-dependent manner. The addition of a restriction enzyme to the protoplast mixture did not have any effect on the frequency of asymmetric hybrids or on the degree of asymmetry in the hybrids produced. UV- and X-irradiation resulted in higher fertility in the hybrids? while PvuII treatment did not have any effect on seed set. A significant positive correlation between degree of asymmetry in different plants and seed set after selfing was detected.