Origin of Nicotiana tabacum L. detected by polypeptide composition of Fraction I protein.

Abstract

THERE is no well-authenticated record of the occurrence of Nicotiana tabacum, the commercial tobacco plant, in the wild state, and so its origin and evolution are of great interest. N. tabacum (n=24) is believed to have arisen by chromosome doubling after hybridisation of N. sylvestris Spegazzini and Comes (n = 12) with a species in the Tomentosae section of Nicotiana. Goodspeed and Clausen1 suggested that N. tomentosa Ruiz and Pavon (n = 12) was the species, but Clausen2 amended it to N. tomentosiformis Goodspeed (n = 12). Goodspeed3 favoured N. otophora Grisebach (n = 12), however, because of its present-day geographical distribution; N. otophora is found together with N. sylvestris in an area on the eastern slopes of the Andes whereas N. tomentosiformis occurs further north where N. sylvestris has not been found. Later evidence, however, suggests N. tomentosiformis as the more likely progenitor of N. tabacum. Gerstel4, from an analysis of the segregation of artificial polyploids of N. tabacum × N. tomentosiformis and N. tabacum × N. otophora, concluded that N. tomentosiformis showed the greater chromosome homology with N. tabacum, and Sheen5–7 from an analysis of isoenzyme patterns and sterol composition supported the conclusion that N. sylvestris and N. tomentosiformis were the likely progenitors of N. tabacum. From an analysis by isoelectric focusing of the polypeptide composition of Fraction I protein isolated from N. tabacum and the putative progenitor species, we now report that N. tabacum arose from the hybridisation of N. sylvestris ♀ × N. tomentosiformis ♂.