USE OF A SUBSET OF DOUBLED-HAPLOLD LINES FOR RAPD INTERVAL MAPPING INBARLEY

Molecular markers have been used in barley to locate genes and quantit ative trait loci. Only a few RAPD markers have been located on barley marker maps. The objectives of this study were (i) to place RAPD marke rs in specific intervals on the barley linkage map developed from the cross Steptoe (S) x Morex (M), (ii) to examine the distribution of RAP D markers, and (iii) to compare markers amplified by Taq DNA polymeras e with those amplified by the Stoffel fragment of Taq DNA polymerase. Screening of DNA from S and M with 362 decamer primers identified 85 t hat amplified 127 reliable RAPDs. A subset of 15 doubled-haploid (DH) lines from the 150 DH line mapping population was used to place these RAPD markers in intervals on the SM map. This subset can be used for r apid placement of any new markers on the SM linkage map. Most of the R APD markers were dominant but four codominant RAPDs were identified. T he RAPDs were not evenly distributed, with many clustered around the c entromeric region of each chromosome. Two of these clusters were locat ed in intervals larger than 15 cM. Testing of 38 to 42 additional DH l ines provided more precise placement of eight of the markers in these clusters. Reliable RAPDs were detected with 44% of the primers tested with the Stoffel fragment, but with only 17% of the primers tested wit h Taq DNA polymerase. These RAPDs provide additional markers for use i n barley improvement.