Meiotic instability in Aegilops cylindrica: a comparison with stable meiosis in Triticum monococcum subsp aegilopoides

Wild relatives of wheat are potential sources of genetic variation for wheat improvement. Meiosis is a complex and multistep process involving many genes in which the underlying mechanisms have yet to be fully elucidated. In this study, the meiotic behavior of eight genotypes of Triticum monococcum subsp. aegilopoides and eight genotypes of Aegilops cylindrica which naturally grow side-by-side in four different regions in West Iran was investigated. Immature spikes were fixed in Carnoy's solution and stained with hematoxylin. Percentage of abnormalities at different meiotic stages and meiotic index were determined. Results indicated the higher meiotic abnormalities in Ae. cylindrica including laggards, chromosome stickiness and bridges, B chromosomes, chromosomal unequal distribution, asynchrony, micronuclei, abnormal localization of the daughter nucleus, absence of spindle fibers and 2n gamete formation. The meiotic index of 82.6% calculated for this species characterized it as having relatively unstable meiotic behavior. Meiotic abnormalities were observed in T. m. subsp. aegilopoides, including laggard, chromosome stickiness and bridge, abnormal localization of daughter nucleus and 2n gamete formation. Given the calculated meiotic index of 97.1%, this species can be categorized as having a stable meiotic behavior. Both inter and intraspecific variations were revealed for 2n gamete formation between two species and among eight genotypes within each species examined. It is concluded that the rich array of meiotic instabilities and in particular 2n gamete production in Ae. cylindrica, which grows side by side with T. monococcum subsp. aegilopoides in West Iran, may add to the species diversity in this region.