Meiotic Restitution and the Origin of Polyploidy. Ii. Prolonged Duration of Metaphase I as Causal Factor of Restitution Induction

The meiosis of nine F1 hybrids (2n = 35) between one Triticum crassum (2n = 42) genotype and nine T. turgidum genotypes showed a strong positive correlation between the degree of lagging of univalents at anaphase I and the degree of occurrence of restitution. Where lagging was extremely high (90–100%) almost all meiotic cells formed restitution nuclei early in anaphase I, producing seed and a viable, polyploid (2n = 70) offspring. Further analysis showed that restitution was probably induced by a prolonged metaphase I, induced by the high degree of meiotic irregularities and strong lagging during anaphase I. These and other factors that interact in these highly irregular meioses and lead to restitution and the production of polyploid seeds are discussed in detail.