Cytogenetic studies in hexaploid Helianthus species and their F1 hybrids with cultivated sunflower, H. annum

Hexaploid sunflower species provide potential sources of desirable genes in breeding for resistance to pathogens as well as high protein and oleic acid content. The possibility of using them in sunflower breeding was studied by testing the crossability of hexaploid species to cultivated sunflower, by the analysis of meiosis and pollen viability in the F₁ interspecific hybrids. The hybrids were obtained from 16 combinations, with 1–18 F₁ plants per combination. The F₁ hybrids in general exhibited the dominant phenotype of the wild species. Sterility ranged from 0 to 87.5% per F₁ combination, while pollen viability ranged from 43.0 to 70.2%. Meiosis was almost normal in the species analysed but irregular in the F₁ hybrids. Most of the meiocytes showed predominantly bivalents (86.79–90.22%), but univalents (0.00–4.99%) and the multivalents (8.23–10.09%) occurred as well. At anaphase I, chromosome bridges were detected in 6.88–8.48% of meiocytes. Fast chromosomes in meta-phase I and lagging chromosomes in anaphase I and telophase II were observed in many meiocytes.