6S mapping

--Doug Mead, Russ Kwan, Mike Flaherty and Ed Weck

We have begun to create an integrated chromosome 6S map using morphological, isozymic and phenotypic marker data. As a preliminary step in establishing the most polymorphic cross, Stock Center lines (courtesy of E. B. Patterson) 601 A-G, 602 A-E, 603 B and 603 D were planted in Stanton in the summer of 1989 and analyzed with RFLP probes NPI7, UMC85, BNL6.29, BNL7.28, and NOR and the isozyme Pgd1. Line 601E (ms6 x ms6/+; 78-599-4/-5) was polymorphic for the above mentioned RFLP and isozyme markers and an ear heterozygous for all markers was selected for further mapping studies.

117 plants from the selfed ear were sampled for Pgd1 isozyme analysis and planted in the greenhouse. Although the plants showed early signs of stress, possibly due to tissue sampling for isozyme analysis, all plants could be scored for polymitotic. 116 plants (one plant gave bad DNA) were analyzed with the RFLP probes NPI7, UMC85, NOR, BNL6.29, BNL7.28.

Isozyme and RFLP data were analyzed with Mapmaker (Lander et al. Genomics 1:174, 1987). A program was written in Fortran to compare ms6 = po phenotypic data with RFLP and isozyme genotypic data using maximum likelihood equations from Allard, Hilgardia 24:235 (1956).

The 6S map in Figure 1 shows the distances between the 6S isozyme and RFLP markers as determined in Mapmaker. In this cross, the Fortran program shows the map position of po to be identical with that of UMC85. Additional crosses will be made in order to integrate ragged, wilted, and piebald leaves into the map.

Figure 1., 6S Map


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