Heterochromatin and rDNA patterns in Solanum species of the Morelloid and Dulcamaroid clades (Solanaceae)

Abstract

The heterochromatin distribution and the position of 18-5.8-26S and 5S rDNA loci were determined in 13 species of Solanum of the Morelloid and Dulcamaroid clades. The CMA/DAPI staining and FISH was employed. Two types of constitutive heterochromatin were determined: CMA+/DAPI- associated to NOR and CMA+/DAPI- distributed as terminal bands. In the Morelloid clade, CMA+/DAPI- bands were found in five species, while in the Dulcamaroid clade, only S. angustifidum presented this feature. In the Morelloid clade, from two to four 18-5.8-26S rDNA loci occupied terminal positions, and 2 rDNA 5S loci were found with variable positions (terminal, intercalary and centromeric). In the Dulcamaroid clade, two terminal 18-5.8-26S rDNA loci were detected, with the exception of S. salicifolium, which possessed four such loci and two to four 5S rDNA loci. Solanum crispum is the only species possessing the 5S in synteny with 18-5.8-26S rDNA loci. Karyotype features, chromosome banding pattern as well as the location of ribosomal genes varied among the species, reflecting the chromosome differentiation and evolutionary divergence. The findings obtained contributed to the development of tools that can be used for establishing chromosomic homeologies among species and hence to clarify their taxonomic relationships.