Cytogenetic analysis of plants regenerated from tissue explants and mesophyll protoplasts of winter rape, Brassica napus L.

Abstract

Plants were regenerated from seedling tissue explants of four lines of winter rape (Brassica napus L.) including a cytoplasmic male sterile line carrying Raphanus sativus L. cytoplasm, and from leaf mesophyll protoplasts of the cytoplasmic male sterile line. Chromosome number variability was investigated in 102 regenerated plants. Mitotic root-tip cells were scored initially; those plants exhibiting mixoploidy or an altered chromosome number were reexamined at meiosis to confirm the presence of alterations in germ line cells. Plants regenerated from seedling explants included 2n = 38 diploids (87.0%) similar to the parental line, monosomics (7.8%), trisomics (2.6%), and 2n = 76 tetraploids (1.3%). The germ line number was not resolved in one mixoploid (1.3%). Protoplast-derived regenerated plants were diploid (44%), hypodiploid (20%), and tetraploid or hypotetraploid (36%). Meiotic analysis of regenerated plants showed a range of multiple chromosome associations with no plants consistently exhibiting bivalent formation only. Chromosomal alterations other than number may have been induced by culture, but could not be substantiated since multiple chromosome associations were also frequent in control plants grown from seed.Key words: plant regeneration, protoplast regeneration, Brassica napus, cytogenetics.