Genome organization of Brassica napus and Lesquerella fendleri and analysis of their somatic hybrids using genomic in situ hybridization

Abstract

Construction of Brassica napus (2n = 38) and Lesquerella fendleri (2n = 12) karyotypes revealed that B. napus contains 10 pairs of metacentric, 5 pairs of submetacentric, and 4 pairs of subtelocentric chromosomes, while L. fendleri contains 6 pairs of metacentric chromosomes that are, on average, 1.5 times longer than those of B. napus. By analysing the karyotypes and performing genomic in situ hybridization (GISH), the chromosome complements of somatic hybrids produced between Brassica napus (+) Lesquerella fendleri were studied. Protoplasts fused with no pretreatment, symmetric fusions, resulted in hybrids containing L. fendleri chromosomes in numbers varying from 2 chromosomes to 2 chromosome complements. In the asymmetric fusion experiments, in which L. fendleri protoplasts were irradiated before fusion, plants with from 38 to more than 76 chromosomes were obtained. In the hybrids with 38 chromosomes, the presence of L. fendleri chromosomes was not detected by GISH analysis, even though L. fendleri DNA was revealed by Southern blotting. Intra- and inter-genomic recombinations were observed in hybrids from both symmetric and asymmetric fusions. The rearrangements were more prevalent in plants resulting from asymmetric fusions. Modifications of the phenotype and reduced fertility of the hybrid plants were correlated with increased dosages of the L. fendleri genome. At least one genome complement of L. fendleri was required to express its morphological features.Key words: Agrobacterium rhizogenes transformed root cultures, Brassica napus, Lesquerella fendleri, somatic hybrids, chromosome translocation.