Competition of Parental Genomes in Plant Hybrids

Abstract

Interspecific hybridization represents one of the main mechanisms of plant speciation. Merging of two genomes from different subspecies, species, or even genera is frequently accompanied by whole-genome duplication (WGD). Besides its evolutionary role, interspecific hybridization has also been successfully implemented in multiple breeding programs. Interspecific hybrids combine agronomic traits of two crop species or can be used to introgress specific loci of interests, such as those for resistance against abiotic or biotic stresses. The genomes of newly established interspecific hybrids (both allopolyploids and homoploids) undergo dramatic changes, including chromosome rearrangements, amplifications of tandem repeats, activation of mobile repetitive elements, and gene expression modifications. To ensure genome stability and proper transmission of chromosomes from both parental genomes into subsequent generations, allopolyploids often evolve mechanisms regulating chromosome pairing. Such regulatory systems allow only pairing of homologous chromosomes and hamper pairing of homoeologs. Despite such regulatory systems, several hybrid examples with frequent homoeologous chromosome pairing have been reported. These reports open a way for the replacement of one parental genome by the other. In this review, we provide an overview of the current knowledge of genomic changes in interspecific homoploid and allopolyploid hybrids, with strictly homologous pairing and with relaxed pairing of homoeologs.

Subgenome evolution in allotetraploid plants

“…Self‐fertilization could be expected to reduce subgenomic intermixing. In fact, the genomes contained in the self‐fertilizing gametes originate from the same plant, drastically reducing the impact of parental genetic diversity on the hybrid genome’s stability (Glombik et al , 2020). In the case of wild and domesticated emmer wheat, both are self‐fertilizing plants with outcrossing rates below 5% (Dvorak, 2013; Sahri et al , 2014).…”

Reciprocal allopolyploid grasses (Festuca × Lolium) display stable patterns of genome dominance

“…These include numerous forms of chromosomal rearrangements as well as mitotic and meiotic abnormalities (Glombik et al. , 2020 ). In addition to structural genomic changes, allopolyploidy is often accompanied by genome‐wide gene expression alterations (Yoo et al.…”

Detecting Introgressed Populations in the Iberian Endemic Centaurea podospermifolia through Genome Size

“…Understanding the ecological and evolutionary consequences of this puzzling phenomenon has therefore become a source of intense debate [ 12 , 22 , 23 , 24 ]. Part of such interest is underpinned by the fact that, despite the expectancy that hybrids would (theoretically) display intermediate genomic features concerning the parental genomes [ 25 ], several studies report that, in many cases, one of the parental genomes can become dominant and erode the signature of the other parental genome [ 26 , 27 , 28 ]. In this sense, the pattern found in C. podospermifolia , whose likely introgressed populations present genome sizes close to their sympatric congeners and quite divergent from the isolated conspecific population ( Figure 1 C), in a similar way than what was observed in Armeria [ 29 ], could reflect a process of genomic assimilation.…”