The Effect of Temperature on the Male and Female Recombination Landscape of Barley

In barley (Hordeum vulgare L.) and potentially many other members of the Pooideae, up to a third of genes are largely inaccessible to conventional breeding programmes as meiotic crossovers are localised to the ends of the chromosomes. There is however evidence that environmental stress can affect crossover patterns so we utilised a genome-wide marker set for linkage analysis combined with cytological mapping of crossover events to examine the recombination landscape of plants grown at different temperatures. We found that barley shows heterochiasmy i.e. differences between female and male recombination frequencies at higher temperatures. In addition, we found that elevated temperature significantly changes patterns of recombination in male meiosis only, with a re-positioning of Class I crossovers determined by cytological mapping of HvMLH3 foci. We show that the length of synaptonemal complexes in male meiocytes also increases in response to temperature

The results demonstrate that the distribution of crossover events are malleable in barley and can be shifted to proximal regions by altering the growth temperature. The shift in recombination is the result of altering the distribution of Class I crossovers, but the higher recombination at elevated temperatures may not be the result of solely an increase in Class I events. 

The implications of these results will be discussed in terms of the control of recombination landscape in barley as well as the potential applications to cereal breeding programmes.