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 c ytometry method. The nuclei were isolated mechanically or via protoplasts f rom 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 obtain ed from suspension cultured cells by lysis of protoplasts. The source and t he method of nuclei isolation affected the pattern of nuclear DNA in the ge notypes studied. The mesophyll nuclei showed two distinct peaks on the DNA histograms, whereas the DNA peaks produced by cell suspension nuclei were b road 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 meso phyll nuclei than in those obtained from the cell suspension for the same g enotypes. The results are discussed in respect of the genetic instability o f Solanum genotypes. The usefulness of a flow cytometry approach in somatic hybridization research is also discussed.