A PHYSIOLOGICAL AND MOLECULAR ANALYSIS OF THE GENUS NICOTIANA

An analysis of the evolution of the genus Nicotiana was carried out wi th physiological and molecular tools. The capacity of explants from se edlings of several species of Nicotiana to differentiate roots or shoo ts or to habituate was used to ascertain whether the in vitro behavior of species has a nonrandom distribution in the genus. The results obt ained allowed us to identify two groups of species, one root-forming p rone composed of Paniculatae (subgenus Rustica) and the composed of Al atae, Repandae, and Noctiflorae (subgenus Petunioides), with a major t endency toward the production of shoots. Habituation capacity was char acteristic of species randomly distributed throughout the phylogenetic tree. These data suggest fixation throughout the evolution of coadapt ed gene complexes (hormone-related genes) involved in the control of d evelopmental processes, RAPDs, on the other hand, used as molecular ma rkers for the clustering of related species, seem entirely coherent bo th with classical morphological and karyological studies and with in v itro physiological methods, supporting an early subdivision of the who le genus into two diverging developmental patterns. (C) 1997 Academic Press.