GENOME SCANNING FOR RESISTANCE-GENE ANALOGS IN RICE, BARLEY, AND WHEAT BY HIGH-RESOLUTION ELECTROPHORESIS

Genes cloned from diverse plants for resistance to different pathogens have sequence similarities in domains presumably involved in pathogen recognition and signal transduction in triggering the defense respons e. Primers based on the conserved regions of resistance genes often am plify multiple fragments that may not be separable in an agarose gel. We used denaturing polyacrylamide-gel electrophoresis to detect PCR pr oducts of plant genomic DNA amplified with primers based on conserved regions of resistance genes. Depending upon the primer pairs used, 30- 130 bands were detected in wheat, rice, and barley. As high as 47%, 40 %, and 27% of the polymorphic bands were detected in rice, barley, and wheat, respectively, and as high as 12.5% of the polymorphic bands we re detected by certain primers in progeny from a cross of the wheat cu ltivars 'Stephens' and 'Michigan Amber'. Using F-6 recombinant inbred lines from the 'Stephens' x 'Michigan Amber' cross, we demonstrated th at polymorphic bands amplified with primers based on leucine-rich repe ats, nucleotide-binding sites and protein kinase genes, were inherited as single loci. Linkages between molecular markers and stripe rust re sistance genes were detected. This technique provides a new way to dev elop molecular markers for assessing the genetic diversity of germplas m based upon potential candidate resistance genes in diverse species.