Complete uniparental chromosome elimination occurs in some plant interspecific and intergeneric hybrid combinations. This phenomenon precludes viable hybrids from developing and results in haploid embryo formation of only one of the parents. It is, therefore, a major barrier for introgressing desirable traits from wild species into crop plants and breeding new crop species. We will investigate selective elimination of parental chromosomes during the development of hybrid embryos by using crosses in the genus Hordeum as a model since the degree of chromosome retention is influenced by parental genotype and environmental conditions after fertilisation. Once the crosses are made our aims are first, to establish whether a genome dosage exists to promote or retard elimination; second, to characterise the tissue-specific nature of elimination; and third, to identify which barley chromosomes are involved in elimination. We will use combined immunostaining methods and cytogenetic analyses to determine the activity and location of the highly conserved histone H3-like centromeric protein A (CENH3), which acts as a regulator of the mitosis-dependent elimination process. The knowledge gained should result in immense benefits accruing to agriculture by allowing the prediction of suitable crosses for either haploid or hybrid plants, both of which can be used in practical plant breeding programmes. Furthemore, we will make a huge step forward in our understanding of the interaction of parental genomes in newly-formed hybrids to provide valuable new insights into species evolution.