The application of immunological methods to the taxonomy of species within the genus Solanum

Abstract

The application of immunological analysis to plant taxonomy has been made practicable by the development of gel-diffusion methods, both by the Elek-Ouchterlony technique and by the more recent immuno-electrophoretic technique of Grabar & Williams. By these means individual proteins in plant extracts may be differentiated and a number of components in the extracts compared individually with those from related species. A modification of these methods has been applied to the investigation of the genus Solanum , with particular reference to the inter-relationships of certain Mexican species of potato with one another and with S. tuberosum , the domestic potato. Antisera were raised in rabbits to crude saps from S. tuberosum and S. ehrenbergii (a Mexican species), using a combination of Freund’s adjuvant technique with courses of intravenous injections. With both antisera well-marked precipitation lines developed against extracts from all the thirty-eight species examined; and by comparison of the direct ‘line-spectra’ and those obtained after cross-absorption of an antiserum, it was possible to divide the species into groups. The results show in their main outline a remarkably close agreement with those obtained from the classical taxonomic methods, and with the general conclusions arrived at from cytological and genetical studies. The value and the limitations of these immunological techniques as applied to taxonomic studies are discussed.