Chromosome number and genome size diversity in five Solanaceae genera

Abstract

Sixteen species of Solanaceae, belonging to five genera, were studied karyologically through chromosome counting, chromosomal measurement, and karyotype symmetry. Genome size (GS) estimation was performed on fifteen species using flow cytometry. The chromosome number 2n=24 was found in all Solanum species and Acnistus arborescens, 2n=22 was found in Brunfelsia uniflora, and 2n=16 in Cestrum representatives. Physalis pubescens was the only specie with evidence of polyploidy, showing 2n=4x=48 chromosomes. The chromosome numbers of S. adspersum, S. inodorum, S. flaccidum, S. sanctae-catharinae, and B. uniflora were reported for the first time. Haploid karyotype length (HKL) was statistically different between the studied species. The polyploid P. pubescens showed the largest HKL value, 93.10 µm. In general, karyotypes were symmetrical with predominance of metacentric chromosomes.  Chromosome size was small in most species (<4 µm), while S. diploconos, C. laevigatum, and C. mariquitense, species with high HKL values, exhibited larger chromosomes. Genome size estimation were unpublished for ten studied species and were the first estimation for the genera Acnistus, Brunfelsia and Physalis. Were observed about eight-fold differences between species with averages varying from 2C=2.57 pg to 2C=20.27 pg. As both HKL and GS showed a continuous variation. We observed partial similarity in the species ordered according to HKL and GS. The Solanaceae genera showed a constant chromosome number and a tendency to posse symmetrical karyotypes.  The genome size also showed differences, which suggests that chromosome evolution in the group could be driven by alterations in the repetitive fractions of the genome.