Co-segregation of nitrate-reductase activity and normal regeneration ability in selfed sibs of Nicotiana plumbaginifolia somatic hybrids, heterozygotes for nitrate-reductase deficiency.

The nitrate-reductase (NR) defective cell lines of Nicotiana plumbaginifolia isolated in our laboratory could not be regenerated into plants on the standard medium (Márton et al. 1982 a). The normal regeneration potential, however, was restored in somatic hybrids obtained by fusing the NR(-) (green) lines with a pigment deficient (P(-)), but NR(+) line, A28. Somatic hybrid plants were fertile in two combinations (A28 + NA9 and A28 + NX9). As expected, segregation for NR(-) and P(-) was found after selfing the somatic F1 (SF1) obtained by protoplast fusion, and in the F2. The variable segregation ratios are explained by chromosome abnormalities. Co-segregation of the NR(-) phenotype and the altered response to shoot induction on standard medium suggest the involvement of the nitrate-assimilatory pathway in determining shoot regeneration ability.