GENERATION OF A YAC CONTIG ENCOMPASSING THE EXTRA GLUME GENE, EG, IN RICE

We have used DNA markers from a high density molecular map of rice (Or yza sativa) to tag a single gene expressed as a flower morphogenesis m utation, extra glume (eg). Using an F-2 population segregating for eg, obtained from a cross between IR24 and F(13)6 (eg/eg), we constructed a partial molecular map and located eg relative to restriction fragme nt length polymorphism markers. The region between two markers appears to span the eg locus on rice chromosome 1 and extends to a genetic le ngth of 3.8 cM. The yeast artificial chromosome (YAC) library obtained from rice variety 'Nipponbare', which carries the wild-type allele of eg, was screened to completely cover the locus by overlapping YAC clo nes. The eg allele should be contained in two overlapping YACs. YAC si ze determination by pulsed-field gel electrophoresis indicated that th is region has a physical length of approximately 400 kb. We anticipate that the tagging of eg in a relatively short stretch of DNA will allo w a molecular characterization of this gene through map-based cloning.