Polyploidization, or whole genome duplication (WGD), has an important role in evolution and speciation, particularly in plants. One of the biggest challenges faced by a new polyploid is meiosis, particularly, discriminating between multiple related chromosomes so that only homologous recombine to ensure regular chromosome segregation and fertility. Triticeae, an economically important tribe which includes crops such as wheat, barley and rye, has been extremely successful in taking advantage of this speciation mechanism. Moreover, this huge capacity for interspecific hybridization among the Triticeae has been used by breeders to transfer interesting traits from related or wild species into crops, particularly into modern wheat. Thus, for both reasons, to study polyploidisation and to facilitate the exchange of genetic material among species, it is very important to understand the genetic relationship among these species and the meiotic behaviour of their chromosomes when they are put together in the same nucleus.

In this study, we report and describe the production of two new intergeneric hybrids formed by the genomes of species from three different genera inside the Triticeae tribe: a trihybrid between Aegilops taushii (DD), Hordeum chilense (H^chH^ch) and Secale cereale (RR) with the haploid genomic constitution DH^chR (n = 7x = 21 chromosomes); and a trihybrid between Triticum durum (AABB), H. chilense and S. cereale with the haploid genomic constitution ABH^chR (n = 7x = 28 chromosomes). We used fluorescence in situ hybridisation (FISH) to establish the chromosome composition of the new hybrids and to study their meiotic behaviour at metaphase I. Interestingly, there were multiple chromosome associations at metaphase I in both hybrids, indicating the presence of crossover formation between the different genomes. The number of associations was clearly higher in the DH^chR hybrid. This is probably due to the absence of the B genome where the Ph1 locus, responsible for controlling homologous recombination in wheat, is present. We also used immunolocalization of key meiotic proteins and observed that the level of synapsis among chromosomes was also higher in the DH^chR hybrid. Finally, we tried to duplicate both hybrids to obtain the corresponding diploid amphiploid, achieving success with the ABH^chR hybrid. Several amphiploids AABBH^chH^chRR were obtained and characterised using both FISH and immunolocalization of meiotic proteins. All the findings will be discussed in detail.

These results indicate that recombination between the genera of three economically important crops is possible. Further work is still needed to recover these recombination events.