FINE PHYSICAL MAPPING OF PH1, A CHROMOSOME-PAIRING REGULATOR GENE IN POLYPLOID WHEAT

The diploid-like chromosome pairing in polyploid wheat is controlled b y the Ph1 (pairing homoeologous) gene that is located on chromosome ar m 5BL. By using a combination of cytogenetic and molecular techniques, we report the physical location of the Ph1 gene to a submicroscopic c hromosome region (Ph1 gene region) that is flanked by the breakpoints of two deletions (5BL-1 and ph1c) and is marked by a DNA probe (XksuS1 ). The Ph1 gene region is present distal to the breakpoint of deletion 5BL-1 but proximal to the C-band 5BL2.1. Two other DNA probes (Xpsr12 8 and Xksu75) flank the region-Xpsr128 being proximal and Xksu75 being distal. The estimated size of the region is less than 3 Mb. The chrom osome region around the Ph1 gene is high in recombination as the genet ic distance of the region between 5BL-1 breakpoint and C-band 5BL2.1 ( not resolved by the microscope) is at least 9.3 cM.