GENOME ORGANIZATION OF BRASSICA-NAPUS AND LESQUERELLA-FENDLERI AND ANALYSIS OF THEIR SOMATIC HYBRIDS USING GENOMIC IN-SITU HYBRIDIZATION

Construction of Brassica napus (2n = 38) and Lesquerella fendleri (2n = 12) karyotypes revealed that B. napus contains 10 pairs of metacentr ic, 5 pairs of submetacentric, and 4 pairs of subtelocentric chromosom es, while L. fendleri contains 6 pairs of metacentric chromosomes that are, on average, 1.5 times longer than those of B. napus. By analysin g the karyotypes and performing genomic in situ hybridization (GISH), the chromosome complements of somatic hybrids produced between Brassic a 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 chromo some complements. In the asymmetric fusion experiments, in which L. fe ndleri protoplasts were irradiated before fusion, plants with from 38 to more than 76 chromosomes were obtained. In the hybrids with 38 chro mosomes, the presence of L. fendleri chromosomes was not detected by G ISH analysis, even though L. fendleri DNA was revealed by Southern blo tting. Intra- and inter-genomic recombinations were observed in hybrid s from both symmetric and asymmetric fusions. The rearrangements were more prevalent in plants resulting from asymmetric fusions. Modificati ons of the phenotype and reduced fertility of the hybrid plants were c orrelated with increased dosages of the L. fendleri genome. At least o ne genome complement of L. fendleri was required to express its morpho logical features.