o12 and cp2 are allelic to dek7
--Philip S. Stinard and Patrick S. Schnable

We reported the location of o12 to the short arm of chromosome 4 in last year's MNL (67:10, 1993). Because of the similarities in phenotype of o12 and dek7 (sugary/shrunken endosperm, aleurone mosaicism, striate seedlings), which is also on 4S, allelism tests were conducted between these two mutants. Nonmutant kernels from selfed segregating ears of dek7 and o12 heterozygotes were planted in our 1992-1993 winter nursery, and the resulting plants were intercrossed between families. Several segregating ears were obtained, indicating allelism between o12 and dek7.

Because of the similarities in phenotype between cp2 (reportedly on chromosome 7) and dek7, allelism tests were conducted between these two mutants. Nonmutant kernels from selfed segregating ears of dek7 and cp2 heterozygotes were planted in the 1993 Urbana summer nursery, and allelism tests were conducted as described above. Several segregating ears were obtained, indicating allelism between cp2 and dek7. (Linkage tests of cp2 with wx T7-9(4363) (7 ctr.; 9 ctr.) demonstrated independent segregation, also indicating that the original placement of cp2 to chromosome 7 was in error.) Allelism tests of cp2 with dek5 (on 3S), which also has a phenotype similar to that of cp2, were negative.

Of the three mutants, cp2 has precedence (Neuffer et al., The Mutants of Maize, 1968), so the recommended nomenclature for o12 and dek7 is cp2-o12 and cp2-dek7. 

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