Karyological relationships among some South American species of Solanum (Solanaceae) based on fluorochrome banding and nuclear DNA amount

Abstract

Fluorescent chromosome banding and measurements of nuclear DNA content by image cytometry of Feulgen-stained cells were performed in one sample each of eight diploid (2n = 24) species of Solanum: S. endoadenium, S. argentinum, S. pseudocapsicum, S. atropurpureum, S. elaeagnifolium, S. sisymbriifolium, S. chenopodioides, and S. palustre. The species studied could be distinguished by heterochromatin amount, banding patterns, and genome size. They exhibited only GC-rich heterochromatin and showed a comparatively low heterochromatin amount (expressed as percentage of haplotype karyotype length), ranging from 2.10 in S. argentinum to 8.37 in S. chenopodioides.<br />Genome size displayed significant variation between species, with 1C-values ranging from 0.75 pg (735 Mbp) in S. palustre to 1.79 pg (1,754 Mbp) in S. sisymbriifolium. No significant correlation between genome size and heterochromatin amount was observed, but<br />intrachromosomal asymmetry index (A1) was negative and significantly correlated with heterochromatin amount. DNA content was positively and significantly correlated with<br />karyotype length. DNA C-value distribution in the genus as well as karyotype affinities and relationships between species are discussed in relation to different infrageneric classifications of Solanum.