AFLPs and existence of hybrids that confuse species boundaries between the lesser known African taxa in Solanum Merolloids section (Solanaceae)

Abstract

Abstract This study was designed to assess whether or not existed interspecific hybrids that confused the taxonomy of African section Solanum species. Hybridization is one of the factors that blur boundary between closely related species. It is an indication that there is semi-permeable boundary between them through which genes are flowing across. In the African species of section Solanum it has been hypothesized that interspecific hybridization is one of the factors complicates the delimitation of species though this claim has never been examined systematically. One group of taxa with complicated taxonomy is the lesser known Bitter species; Solanum tarderemotum and S. florulentum all described from Tanzania. Through history the two taxa have been considered separate species, different species mixed with hybrids and recently the boundary of S. tarderemotum has been expanded to also cover S. florulentum and materials that have been hypothesized to be hybrids. DNA was isolated from sixty-three individuals from 22 accessions and two AFLP primer combinations; EcoRI + AAC/MseI + CAC and EcoRI + ACC/MseI + CAT. Clustering were constructed using PAST software. Five clusters were generated, S. tarderemotum sensu stricto and S. florulentum sensu stricto, fell in different clusters sharing only 41% of their total number of polymorphic bands. The other three clusters were of intermediary forms but sharing larger number of polymorphic bands with S. tarderemotum and S. florulentum than 41%. This observation indicates that the intermediary forms are real hybrids and S. tarderemotum and S. florulentum are good separate species thus should not be fused between them and with their hybrids.