RICE-BARLEY SYNTENY AND ITS APPLICATION TO SATURATION MAPPING OF THE BARLEY RPG1 REGION

In order to facilitate the map-based cloning of the barley stem rust r esistance gene Rpg1, we have demonstrated a high degree of synteny at a micro level between the telomeric regions of barley chromosome 1P an d rice chromosome 6. We have also developed and applied a simple and e fficient method for selecting useful probes from large insert genomic YAC and cosmid clones. The gene order within the most terminal 6.5 cM of barley chromosome 1P was compared with the most terminal 2.7 cM of rice chromosome 6, Nine rice probes, previously mapped in rice or isol ated from YAC or cosmid crones from this region, were mapped in barley . All, except one, were in synteny with the rice gene order. The excep tion, probe Y617R, was duplicated in barley. One copy was located on a different chromosome and the other in a non-syntenic position on barl ey chromosome 1P. The barley probes from this region could not be mapp ed to rice, but two of them were inferred to be in a syntenic location based on their position on a rice YAC. This work demonstrates the uti lity of applying the results of genetic and physical mapping of the sm all genome cereal rice to map-based cloning of interesting genes from large genome relatives.