Fusion-mediated transfer of triazine-resistant chloroplasts: Characterization of Nicotiana tabacum cybrid plants

Summary Terbutryn-resistant plastids of the Nicotiana plumbaginifolia TBR2 mutant were introduced into N. tabacum plants by protoplast fusion following X-irradiation of TBR2 protoplasts. The N. tabacum chloroplast recipient line, SR1-A15, carried mutant (albino) plastids. Following protoplast fusion, potential cybrid cell lines with an N. tabacum (SR1-A15) nucleus and N. plumbaginifolia (TBR2) chloroplasts were identified by their green color. The presence of TBR2 plastids in regenerated green N. tabacum plants was confirmed by hybridization with a chloroplast DNA probe and by the modified chloroplast fluorescence transients characteristic of the TBR2 mutant. Cybrid plants were resistant to high levels of atrazine (10 kg/ha). The protruding stigma and shorter than normal filaments of the cybrids resulted in male sterility. In the cybrids atrazine resistance was associated with reduced vigour, suggesting a causal relationship.