REGENERATION AND CHARACTERIZATION OF PLANTS PRODUCED FROM MATURE TOBACCO POLLEN PROTOPLASTS VIA GAMETOSOMATIC HYBRIDIZATION

Mature pollen protoplasts (n) isolated from kanamycin resistant plants of Nicotiana tabacum (2n = 4x = 48) were fused with somatic mesophyll protoplasts (2n) of Nicotiana plumbaginifolia (2n = 20) to produce pl ants. A total of 3.6.10(6) mature pollen protoplasts were fused with 7 .10(6) mesophyll protoplasts using a PEG/Ca2+ method. Mature pollen pr otoplasts did not divide in our culture conditions, and N. plumbaginif olia protoplasts stopped dividing when the protoplast-derived colonies were transferred to a selection medium containing paromomycine (20 mg .l(-1)). A total of 133 actively growing colonies were recovered on th e selection medium containing kanamycin (100 mg.l(-1)). Plants from tw enty resulting cell lines were confirmed as hybrids (17) or cybrids (3 ) based on leaf and floral morphology and fertility analysis. Isozyme pattern analysis confirmed the nuclear hybrid and cybrid nature, respe ctively, for 2 and 3 typical gametosomatic selected plants. Root tip s quashes of 6 of the gametosomatic hybrid plants revealed chromosome nu mbers ranging from 44 to 68; the 3 selected cybrid plants had 48 chrom osomes. Evidence for organelle transmission from the mesophyll partner in the gametosomatic plants is shown. From the analysis it can be con cluded that the gametosomatic fusion involving mature pollen protoplas ts (n) carrying a dominant selection marker can be convenient for synt hesis of either hybrids or cybrids. Such gametosomatic fusion is there fore considered as a new approach towards the production of androgenet ic plants with a choosen cytoplasm.