CONSERVATION OF FINE-SCALE DNA MARKER ORDER IN THE GENOMES OF RICE AND THE TRITICEAE

DNA markers distributed over large chromosomal regions exhibit conservation of order (collinearity) in different cereal species, but it is not known whether this is maintained on a finer scale, i.e. less than or equal to 2 cM, To address this, sets of two or more genetically linked DNA markers were localised to yeast artificial chromosomes containing rice DNA inserts. Linkage analysis of these DNA markers in barley revealed complete correspondence with their genetic order in rice, the distance between linked sequences on rice chromosomes being <1.6 cM or less than or equal to 1 x 10(6) bp (1 Mb), Thus, DNA markers separated in this range are collinear in rice, barley and, by inference, other members of the Triticeae, These results are discussed with respect to the use of rice as a key system for the isolation of cereal genes.