Search

Abstract. Somatic hybrids between Brassica napus (oilseed rape) and its wild relative Sinapis arvensis (Xinjiang wild mustard) from northwestern China were produced by fusing mesophyll protoplasts. Fifty-four plants were identified as symmetric hybrids and four as asymmetric hybrids by random amplified polymorphic DNA analysis and nuclear DNA content. The morphology of investigated 58 hybrid plants resembled characters from both parental species. Highly fertile hybrids were recovered where the fertility was associated with the choice of B. napus genotype. Enhanced disease resistance to Leptosphaeria maculans was found in S. arvensis and in the hybrid offspring. This plant material has great potentials not only for use as a bridge for the introduction of a number of valuable traits from the wild species to Brassica crops but also for breeding new varieties with improved blackleg resistance.

Abstract:  Chromosome counts and RFLP markers mapped to Arabidopsis thaliana were used to determine the proportion of eliminated chromosomes and retained A. thaliana DNA in the back-crossed (BC) progeny derived from symmetric and asymmetric somatic hybrids between Brassica napus and A. thaliana. All plants were analysed for the presence of two RFLP markers per chromosome, preferably with one located on each chromosome arm. A reduction in both A. thaliana RFLP markers and chromosome numbers was found in the BC1 and BC2 generations of the symmetric hybrids as well as in the BC1 generation of the asymmetric hybrids. In the symmetric hybrids, two back-crosses to B. napus were required to reduce the frequency of retained A. thaliana loci to 42.4% and mean chromosome number to 39.4. In comparison, the BC1 progeny of the asymmetric hybrids had 16% of the analysed A. thaliana loci present and an average of 38.4 chromosomes maintained. When the frequency of A. thaliana chromosomes with both analysed loci maintained was compared with the frequency of chromosomes with one locus lost and one kept, a reduction in the number of complete chromosomes between BC1 and BC2 derived from the symmetric hybrids was observed. Among the BC1 plants in the asymmetric group the situation was different, with higher amounts of incomplete donor chromosomes compared to whole chromosomes. The results indicate that A. thaliana chromosome fragments are more often found in the progeny of irradiated hybrids, while back-crossed symmetric hybrids have more complete chromosomes.

Abstract:  Offspring of somatic hybrids between the zero-erucic acid rapeseed cv Hanna and Lesquerella fendleri were analysed regarding their fatty acid profiles. In the first back-cross generation one plant was found that produced a seed containing up to 16.5% erucic acid and 15% eicosaenoic acid (Line 1), as well as a seed having 4.3% ricinoleic acid (Line 2). This was interpreted as due to a contribution of elongase and hydroxylase genes from the L. fendleri genome since these two fatty acids are not produced in the recipient rapeseed cultivar Hanna. Crosses between Line 1 and cv Hanna resulted in the production of seeds with 35% erucic acid (F2). Furthermore, crosses between the F2 plants and the rapeseed cultivar Gulle, producing 35% erucic acid in the seeds, resulted in F3 seeds with 48% erucic acid. The highest amount of erucic acid, 61.5%, was found in the F6 generation after crossing Line 1 with a high erucic acid rapeseed line, HEAR, followed by self-fertilisation for two generations. When performing Southern-blot analysis on the F6 plants, seven of the nine analysed plants hybridised with the L. fendleri species-specific repetitive probe. The presence of the hydroxylase gene was also observed in the F6 generation of Line 1 according to Southern-blot analysis. Hybridisation with a hydroxylase probe was seen although no hydroxy fatty acids could be detected in any of the F6 plants. In parallel, Line 2 was crossed with HEAR cv Gulle and self fertilised. No hydroxy fatty acids were detected in the F2 generation of Line 2 and no specific hybridisation patterns could be found in the Southern-blot analysis.

Abstract:  Offspring from asymmetric hybrids between Brassica napus and the three B-genome species Brassica nigra, Brassica juncea and Brassica carinata were analysed for the presence of B-genome markers and resistance to the fungus Leptosphaeria maculans, the causal agent of blackleg disease. Twenty five plants from each species combination were analysed in the first backcross (BC1) generation, 30 plants in BC2 and 60 plants in BC3. The plants were analysed by 46 RFLP markers detecting 85 loci dispersed throughout the B. nigra genome. The plants with additional B. carinata DNA had a decrease in the presence of RFLP markers ranging from 59% in BC1 to 36% in BC2 and down to 11% in BC3. Similar results were obtained in the lines with additional DNA from B. juncea where the 60% presence of RFLP markers in BC1 was reduced to 33% in BC2 and to 10% in BC3. However presence of the markers were significantly lower in the B. nigra-derived material where BC1 had 46%, BC2 25% and BC3 8%. Since at least two loci could be detected on each end of the eight linkage groups of the B genome, the degree of symmetry was estimated. After one back-cross between 0.5 and 1.25% intact chromosomes were retained, whereas in BC2 this frequency was 0.21% for all three B-genome donor species. The maintenance of half-chromosomes ranged from 2.63% to 5.38% in BC1 and between 0.73% and 1.15% in BC2. No chromosome arms were found in any of the BC3 plants. In total, four co-segregating markers for cotyledon and adult-leaf resistance to L. maculans were found which detected six loci located on linkage groups 2, 5 and 8. When the results from the three donor species were compared, one triplicate region in the B genome had preserved the resistance loci in all three species.