Nuclear DNA content of Solanum species grown in vitro, as determined by flow cytometry

The DNA relative content in nuclei from several Solanum species, which were used as partners for somatic hybridization, were determined using a flow cytometry method. The nuclei were isolated mechanically or via protoplasts from leaves of in vitro grown plants. In the case of S. nigrum as well as S. tuberosum cv. Bzura and dihaploid clone H8105, the nuclei were also obtained from suspension cultured cells by lysis of protoplasts. The source and the method of nuclei isolation affected the pattern of nuclear DNA in the genotypes studied. The mesophyll nuclei showed two distinct peaks on the DNA histograms, whereas the DNA peaks produced by cell suspension nuclei were broad and less distinct. The DNA content in the nuclei, calculated from the DNA histograms of the samples and a DNA standard historgam (Trout Red Blood Cells, having DNA content of 5.05 pg per nucleus), were much lower in mesophyll nuclei than in those obtained from the cell suspension for the same genotypes. The results are discussed in respect of the genetic instability of Solanum genotypes. The usefulness of a flow cytometry approach in somatic hybridization research is also discussed.