Abstract
Polyploidization, or whole genome duplication (WGD), has an important role in evolution and speciation. One of the biggest challenges faced by a new polyploid is meiosis, in particular, discriminating between multiple related chromosomes so that only homologs recombine to ensure regular chromosome segregation and fertility. Here, we report the production of two new hybrids formed by the genomes of species from three different genera: a hybrid between Aegilops tauschii (DD), Hordeum chilense (HchHch), and Secale cereale (RR) with the haploid genomic constitution HchDR (n = 7× = 21); and a hybrid between Triticum turgidum spp. durum (AABB), H. chilense, and S. cereale with the constitution ABHchR (n = 7× = 28). We used genomic in situ hybridization and immunolocalization of key meiotic proteins to establish the chromosome composition of the new hybrids and to study their meiotic behavior. Interestingly, there were multiple chromosome associations at metaphase I in both hybrids. A high level of crossover (CO) formation was observed in HchDR, which shows the possibility of meiotic recombination between the different genomes. We succeeded in the duplication of the ABHchR genome, and several amphiploids, AABBHchHchRR, were obtained and characterized. These results indicate that recombination between the genera of three economically important crops is possible.
Highlights
Polyploidization or whole genome duplication (WGD) has an important role in evolution and speciation, and it is accepted that all seed plants and angiosperms have experienced multiple rounds of WGD during their evolutionary history [1]
In the case of polyploid wheat, the lack of meiotic recombination between wheat and related species will depend on syntheny, and on a system that appeared during wheat polyploidization to stabilize the wheat genome during meiosis and that has been mainly attributed to the Ph1 (Pairing homoeologous 1) locus [29,30]
We frequently focused on meiotic recombination, but distant hybridization is known to trigger reorganizations of the different genomes [63,64,65], which can be extremely useful in breeding and have often been used to incorporate desirable traits from relatives into wheat [66,67]
Summary
Polyploidization or whole genome duplication (WGD) has an important role in evolution and speciation, and it is accepted that all seed plants and angiosperms have experienced multiple rounds of WGD during their evolutionary history [1]. Many of the world’s most important crops, including wheat, rapeseed, sugarcane, and cotton, are relatively recent allopolyploids This is not a coincidence; allopolyploids often show higher adaptability (they clearly show better tolerance to abiotic stresses), can grow over larger geographical areas, and show better adaptation to the local environment than their diploid progenitors [2]. The reasons for this particular success are not clear, but they are probably the result of multiple evolutionary processes such as rapid genome organisation, fractionation, gene conversion, transgressive gene expression alteration, and suband/or neofunctionalization of duplicate genes [1]. The few allopolyploids that manage to overcome this initial bottleneck of instability, will be able to be established and join the evolutionary fight as efficient competitors of their diploid relative [2]
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