Interspecific differences in differentiation and dedifferentiation patterns in the genus Nicotiana

Differentiation on hormoneless media, habituation ability and crown gall induction in Nicotiana tissue cultures have been used as physiological parameters of evolutionary differentiation between species. Some of them on hormone free media differentiated whole plantlets, others produced only shoots or roots or showed undifferentiated growth (habituation), some eventually died. Moreover, the same genotypes showed a differential behaviour as far as tumor formation by Agrobacterium tumefaciens was concerned. Particularly, the competence for crown gall transformation in Nicotiana species seems negatively correlated with differentiation capacity and may be ascribed to differences in the plants capacity to synthesize growth regulators. The correlation between the results obtained and the phylogenetic position of the genotypes tested is finally discussed.