Mapping of the ij (iojap) locus with RFLP markers

--Chang-deok Han1 and Ed Coe

1present address: Cold Spring Harbor Laboratory

As part of experiments for the transposon tagging of ij, the RFLP (Restriction Fragment Length Polymorphism) markers on the long arm of chromosome 7 were examined to obtain molecular markers linked with the ij locus. The markers located on the long arm of chromosome 7 were obtained from D. Hoisington (University of Missouri), B. Burr (Brookhaven National Lab.), and T. Helentjaris (Native Plants Incorporated). The following RFLP markers were used for this project; UMC56, UMC110, UMC125B, BNL13.24, BNL4.24, NPI435, and NPI283. The ij seedlings were examined among F2 progeny of the cross between Oh51a inbred and ij in Mo17 inbred background. Around 50 ij F2 seedlings were examined. There were limited amounts of DNA because many of the ij seedlings die at the 2-3 leaf stage. Because of the shortage of DNA, not all the seedlings were tested by the same probes. With the help of D. Hoisington,, the RFLP markers were mapped with the computer-aided maximum likelihood program, Mapmaker. The figure shows the calculated linkage map for ij. All the iojap seedlings we examined with markers BNL13.24 and BNL4.24 showed the same patterns of polymorphism as with UMC110. This indicates that the population we worked on was not large enough to detect recombination among the three loci. We did not examine the possibility whether either of the markers, BNL13.24 or BNL4.24, is homologous to UMC110. The DNA marker closest to ij is UMC110, 4.8cM proximal to the gene.

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