[Cytogenetic study of an interspecific hybrid Helianthus praecox x H. annuus, its parental forms and two backcrosses].

Meiosis of wild species (H. praecox) and cultivated sunflower (H. annuus), their F1 interspecific hybrid as well as two backcross generations has been studied. A low level of chromosomal abnormalities in the parents was detected. Interspecific hybridization between the wild and cultivated samples has led to a considerable (50%) increase of meiosis abnormalities in sunflower pollen mother cells. Backcrossing of hybrids by cultivated sunflower decreased the chromosomal abnormalities level to 12.8% in BC1 and 9.6% in BC2. Cytological stability of plants restored in BC2 only.