PRODUCTION OF INTERTRIBAL SOMATIC HYBRIDS BETWEEN BRASSICA-NAPUS L AND LESQUERELLA-FENDLERI (GRAY) WATS

Intertribal Brassica napus (+) Lesquerella fendleri hybrids have been produced by polyethylene glycol-induced fusions of B. napus hypocotyl and L. fendleri mesophyll protoplasts. Two series of experiments were performed. In the first, symmetric fusion experiments, protoplasts fro m the two materials were fused without any pretreatments. In the secon d, asymmetric fusion experiments, X-ray irradiation at doses of 180 an d 200 Gy were used to limit the transfer of the L. fendleri genome to the hybrids. X-ray irradiation of L. fendleri mesophyll protoplasts di d not suppress the proliferation rate and callus formation of the fusi on products but did significantly decrease growth and differentiation of non-fused L. fendleri protoplasts. In total, 128 regenerated plants were identified as intertribal somatic hybrids on the basis of morpho logical criteria. Nuclear DNA analysis performed on 80 plants, using s pecies-specific sequences, demonstrated that 33 plants from the symmet ric fusions and 43 plants from the asymmetric fusions were hybrids. Ch loroplast and mitochondrial DNA analysis revealed a biased segregation that favoured B. napus organelles in the hybrids from the symmetric f usion experiments. The bias was even stronger in the hybrids from the asymmetric fusion experiments where no hybrids with L. fendleri organe lles were found. X-ray irradiation of L. fendleri protoplasts increase d the possibility of obtaining mature somatic hybrid plants with impro ved fertility. Five plants from the symmetric and 24 plants from the a symmetric fusion experiments were established in the greenhouse. From the symmetric fusions 2 plants could be fertilised and set seeds after cross-pollination with B. napus. From the asymmetric fusions 9 plants could be selfed as well as fertilised when backcrossed with B. napus. Chromosome analysis was performed on all of the plants but 1 that wer e transferred to the greenhouse. Three plants from the symmetric fusio ns contained 50 chromosomes, which corresponded to the sum of the pare ntal genomes. From the asymmetric fusions, 11 hybrids contained 38 chr omosomes. Among the other asymmetric hybrids, plants with 50 chromosom es and with chromosome numbers higher than the sum of the parental chr omosomes were found. When different root squashes of the same plant we re analysed, a total of 6 plants were found that had different chromos ome numbers.