METAPHASE AND INTERPHASE FLUORESCENCE IN-SITU HYBRIDIZATION MAPPING OF THE RICE GENOME WITH BACTERIAL ARTIFICIAL CHROMOSOMES

Fluorescence in situ hybridization (FISH) is a powerful tool for physi cal mapping in human and other mammalian species, However, application of the FISH technique has been limited in plant species, especially f or mapping single- or low-copy DNA sequences, due to inconsistent sign al production in plant chromosome preparations, Here we demonstrate th at bacterial artificial chromosome (BAG) clones can be mapped readily on rice (Oryza sativa L.) chromosomes by FISH, Repetitive DNA sequence s in BAC clones can be suppressed efficiently by using rice genomic DN A as a competitor in the hybridization mixture, BAC clones as small as 40 kb were successfully mapped, To demonstrate the application of the FISH technique in physical mapping of plant genomes, both anonymous B AC clones and clones closely linked to a rice bacterial blight-resista nce locus, Xa21, were chosen for analysis, The physical location of Xa 21 and the relationships among the linked clones were established, thu s demonstrating the utility of FISH in plant genome analysis.