Duplicate factors for orange pericarp (orp)

Among the selfed M1 ears from pollen treated with EMS, there appeared one ear which segregated for kernels with orange pigment in the pericarp. The ratio was 15 normal to 1 orange. The ear also segregated 9:7 for purple vs colorless aleurone due to C and R in the treated population. The orange pigment appeared in the pericarp of both the purple and non-purple kernels. Since pericarp is maternal, tissue differences in pigmentation should not segregate among the kernels. Apparently a product from a certain genotype in the underlying endosperm tissue is diffusing into the pericarp, where it causes pigment formation. The ratio of 15:1 suggests duplicate unlinked factors, the double recessive combination being the right genotype for pigment formation. Outcross to a large embryo stock (Aho) with subsequent selfs have repeated the 15:1 segregation. Selfing 17 plants from the normal kernels of a 15:1 ear produced 9 normal ears, 6 ears segregating 3 normal: 1 orange, and 2 ears segregating 15 normal:1 orange. We have tentatively designated these factors orp1 and orp2, although which is which will have to await location of one to chromosome.

When planted, the orange kernels grow into small, narrow leaf, pale green seedlings which grow slowly and die before maturity. SDS PAGE analysis of 18-day endosperm and embryo tissue failed to show protein differences from normal.

M.G. Neuffer and M.T. Chang

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.

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