Taxonomic studies on Solarium section Solarium (Maurella)

Various taxonomic methods are being used to clarify the systematics of Solarium section Solanum , the large and variable species group centring around the black nightshade, S. nigrum. To put the experimental work into perspective, a summary of former taxonomic treatments is given, together with an outline of the provisional taxonomic framework of the section, initially established from earlier classical studies, and supplemented by later experimental work.
Experimentation with living populations has shown that Solanum taxonomy is complicated by several factors. In addition to the historical factors, phenotypic plasticity, genetic variation, the existence of a polyploid series, and the possibilities of interspecific hybridization accompanied by various pre- and post-zygotic isolating mechanisms are dealt with.
The various taxonomic categories attached to Solanum accessions during earlier classical studies derive support from the crossability behaviour of the taxa concerned. Morphological divergence is generally accompanied by genetical isolation which can manifest itself at any time between pollination and the maturation of the F₂ progeny. Data from the hybridization studies, in which 14 diploid species, five tetraploid species, four hexaploid species and one octoploid taxon were used, are presented in detail.