Cytoembryology of infertile segregants of the hybrid Lupinus varius L. x L. digitatus Forsk

In F₂, F₃ and F₄ generations of one hybrid line of Lupinus varius × L. digitatus, segregation into infertile and fertile plants in the ratio 3:1 was observed. Cytoembryological analyses showed that sterility was caused by irregularities in megasporocyte formation, in megasporogenesis and megagametogenesis. The following abnormalities lead to female sterility: no megasporogenic cells separated in nucelluses; in other nucelluses with megaspore mother cells, these cells underwent vacuolation and died before reduction division. In the megaspore mother cells, in which probably meiosis occurs, the megasporocyte division is irregular; a restitution nucleus is frequently formed after reduction division and such megasporocyte develops into an embryo sac. In 8-nucleate embryo sacs a change in the nucellus polarization was observed, while in rarely encountered embryo sacs the embryo cells underwent vacuolation and then died. Female sterility in the studied segregants is determined genetically, whereas sterilization of reproduction cells is a developing process throughout the period of sporocyte and female gametophyte formation.