Chromosome elimination by wide hybridization between Triticeae or oat plant and pearl millet: pearl millet chromosome dynamics in hybrid embryo cells.

Wide crossing is one of a number of practical methods that can be used to expand genetic variation in common wheat (Triticum aestivum). However, in crosses between wheat and distantly related species such as maize (Zea mays) and pearl millet (Pennisetum glaucum), non-wheat chromosomes are often eliminated from the hybrid during embryogenesis. In this study, we used pearl millet pollen to pollinate the pistils of a range of plants in the tribe Triticeae, as well as oat. Seven days after pollination, the dynamics of the pearl millet chromosomes in the embryos were observed using in situ hybridization, probing both the pearl millet genomic DNA and its centromere-specific repeats. In embryos from the crosses with oat, all seven of the pearl millet chromosomes were retained. However, in hybrids with the Triticeae species, chromosome elimination occurred during embryogenesis. Pearl millet chromosome showed chromosome rearrangements and non-disjunction together with micronuclei. These rearranged chromosomes and micronuclei derived from the breakage of bridges and retention of acentric fragments in anaphase, respectively. The cause of the chromosome elimination of wheat-pearl millet hybrid is not malfunction of the kinetochores binding to the spindles but the malfunction of the sister chromatids segregation at anaphase especially of chromosome arm.