Understanding Recombination In Barley and Perspectives For Breeding?

Meiotic crossovers (COs) predominantly occur towards the ends of chromosomes in barley, thus disfavouring the generation of novel gene combinations and useful variation for plant breeders. This reduces the potential for mapping important agronomical traits and creates linkage drag.

We have investigated the factors underlying the skewed chiasma distribution (cytological sites of COs) and show that it reflects polarisation in the spatiotemporal initiation of recombination, chromosome pairing and synapsis. Markers for meiotic recombination are not restricted to the distal chromosomal regions, suggesting that COs may potentially form throughout the chromosomes. However, there is a lag (2-3h) between meiotic events in the distal and interstitial/proximal regions. Consequently meiotic events in the distal regions (but not the interstitial/proximal regions) occur in coordination with the chromatin cycles that are a conserved feature of the meiotic program.

Early recombination initiation is spatially associated with early replicating, euchromatic DNA, which is predominately found in distal regions. We have demonstrated that a modest temperature shift is sufficient to alter meiotic progression in relation to the chromosome cycles. The polarisation of the meiotic processes is reduced and is accompanied by an increase in interstitial and proximal chiasmata suggesting a potential route to modify recombination in barley.