Plant Genome IV Conference Plant Genome IV Conference
In order to facilitate the map-based cloning of the barley stem rust resistance gene Rpg1, we have demonstrated a high degree of synteny at a micro level between the telomeric regions of barley chromosome 1P and rice chromosome 6. We have also developed and applied a simple and efficient methods for selecting useful probes from large insert genomic YAC, BAC, 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 isolated from YAC or cosmid clones from this region, were mapped in barley. All, except one, were in synteny with the rice gene order. The barley probes from this region could not be mapped to rice, but two of them were inferred to be in a syntenic location based on their position on a rice YAC. Several rice probes mapped very close to Rpg1 locus. The closest marker (0.1 cM from Rpg1) was used to identify a rice BAC clone (ca. 150 kb). Over 20 BAC subclones were mapped in barley showing synteny and colinearity. The current Rpg1 region map has bracketing marker 0.1 cM distal and 0.5 cM proximal of Rpg1 and 13 cosegregating markers. This work demonstrates the utility of applying the results of genetic and physical mapping of the small genome cereal rice to map-based cloning of interesting genes from large genome relatives.