Abstract
The tribe Triticeae contains about 500 diploid and polyploid taxa, among which are important crops, such as wheat, barley and rye. The phylogenetic relationships, genome compo-sition and chromosomal architecture, were already reported in the pioneer genetic studies on these species, given their implications in breeding-related programs. Hexaploid wheat, driven by its high capacity to develop cytogenetic stocks, has always been at the forefront of these studies. Cytogenetic stocks have been widely used in the identification of homoeologous relationships between the chromosomes of wheat and related species, which has provided valuable information on genome evolution with implications in the transfer of useful agronomical traits into crops. Meiotic recombination is non-randomly distributed in the Triticeae species, and crossovers are formed in the distal half of the chromosomes. Also of interest for crops improvement is the possibility of being able to modulate the intraspecific and interspecific recombination landscape to increase its frequency in crossover-poor regions. Structural changes may help in this task. In fact, chromosome truncation increases the recombination frequency in the adjacent intercalary region. However, structural changes also have a negative effect upon recombination. Gross chromosome rearrangements produced in the evolution usually suppress meiotic recombination between non-syntenic homoeologs. Thus, the chromosome structural organization of related genomes is of great interest in designing strategies of the introgression of useful genes into crops.
Highlights
The tribe Triticeae Dumort belongs to the subfamily Pooideae of the grass family Poaceae (Gramineae).About 500 taxa are included in this tribe
Homozygotes for the loss of the distal 25% of the 1BL arm, or the distal 41% of 5BL, increase the recombination rate of the middle arm region, without modifying that of the proximal region, relative to wild type plants [149,150]. These results suggest that the position of a segment in the telomere-centromere axis was a decisive factor in its capacity to produce a CO
Modulating the recombination landscape is of supreme importance for crop breeding, since a considerable number of genes with agronomical relevance are located in crossover-poor chromosome regions
Summary
The tribe Triticeae Dumort belongs to the subfamily Pooideae of the grass family Poaceae (Gramineae). Many studies carried out in order to identify the diploid progenitors of the allopolyploid species in the wheat-Aegilops complex were based in the genome analysis developed by Kihara [30,31,32,33] This method assumed that the genetic architecture of the different genomes present in a given allopolyploid is preserved as in their diploid progenitors, making possible their identification through the analysis of meiotic pairing in interspecific crosses. In the case of species belonging to the tertiary gene pool, genomes are more differentiated relative to those of wheat, and any gene transfer to be achieved needs the occurrence of a recombination between homoeologous chromosomes. I will summarize all of the features of meiotic recombination with implications on breeding-related programs, especially those concerning polyploid wheats
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