orange pericarp Duplicate factors orp1 and orp2 give 15:1 ratio of normal vs orange color in overlaying maternal pericarp on homozygous orp1, orp2 kernels from selfed double heterozygous ear. Mutant orp kernels produce weak, narrow leaf, brownish palegreen seedlings with spots, barren nodes and odor of phenol. The orange pericarp duplicate factor mutants present a unique demonstration of the great amount of phenotypic variation that can occurr as the consequence of one or two genetic changes; the production of orange pigment in the pericarp (maternal tissue) that segregate with the kernel (filial tissue) which produce germinating kernels whose roots and shoots flouresce blue under uv light and which produce sickly brownish green mutant seedlings that are morphologically altered and smell like indole. In addition these factors provide excellent demonstration of duplicate factor behavior and linkage and altered genetic transmission in the corn plant.
MaizeGDB reference

orange pericarp Two selfed ears showing 15:1 duplicate factor ratios. Top, colored colorless B1:Peru/b1 (chromosome 2S) and R1-scm/r1 (chromosome 10S). Bottom, colorless and orange pericarp (+/orp1, chromosome 4S) and +/orp2 (chromosome 10S). A good demonstration of duplicate factor ratios. Note that pericarp is a maternal tissue and should have a clear normal phenotype reflecting a +/orp1, +/orp2 maternal genotype as a clear uniform cover over all the filleal kernels beneath, one in 16 of which will be genetically orange (orp1/orp1, orp2/orp2) but unable to express the orange pigment. The pericarp over the double mutant turns orange because the double mutant endosperm secrets phenol which diffuses into the surface maternal tissue and interacts there to produce the bright orange pigment. For another example See orp*-N888D.

orange pericarp kernel: Colored colorless (segregating for c1 and r1) flint selfed M2 origin ear segregating (15:1)for orange color in overlaying maternal pericarp on homozygous orp1, orp2 filial endosperm kernels. Note chip of orange pericarp removed from mutant kernel in lower left. Also note that orp1 (though not visible as such) was already in the ear stock for treated pollen and that orp2 was induced by EMS mutagenesis.

orange pericarp Selfed ears segregating for orange pericarp showing (top) a Duplicate factor 15:1 ratio for the double heterozygote, and (bottom) single factor 3:1 ratio for an ear homozygous recessive for one factor and segregating for the other. Note that pericarp is a maternal tissue and should have a clear normal phenotype reflecting a +/orp1, +/orp2 maternal genotype as a clear uniform cover over all the filleal kernels beneath, one in 16 of which will be genetically orange (orp1/orp1, orp2/orp2) but unable to express the orange pigment. The pericarp over the double mutant turns orange because the double mutant endosperm secrets phenol which diffuses into the surface maternal tissue and interacts there to produce the bright orange pigment. For another example See orp*-N888D.

orange pericarp presence of indole: Germinating normal and orange pericarp kernels with coleoptiles and root; the normal is on the left and the mutant is on the right. The photo is the result of a mixture of incandescent white light and UV light showing blue fluorescence of the mutant coleoptile and root. (Photo courtesy A. Wright). (ph Mutants of Maize)

orange pericarp Surviving orp1 orp2 plant, grown under optimal conditions in the greenhouse, showing brownish color, narrow leaves and failure to develop at nodes. Plant gave off strong odor of indole.

orange pericarp Selfed Ga1 su1+/ ++orp1, orp2 orp2 ear showing excess of nonsugary orange pericarp kernels and of su1 kernels, indicating linkage of Ga1 su1 and orp1 and alteration of transmission of this segment due to Ga1

orange pericarp selfed ear of an orp1/orp1, +/orp2 plant segregating 3:1 for orange pericarp, orp2-N1186B.

orange pericarp kernel: Colored colorless (segregating for c1 and r1) flint selfed M2 origin ear segregating (15:1)for orange color in overlaying maternal pericarp on homozygous orp1, orp2 filial endosperm kernels. Note chip of orange pericarp removed from mutant kernel in lower left. Also note that orp1 (though not visible) was already in the ear stock for treated pollen and that orp2 was induced by EMS mutagenesis.

orange pericarp orp*-888D: This mutant was probably orp1 and was already in one of the treatment parents thus forming an orp duplicate pair with either mn4 or cp3 one of which is likely an allele of orp2.

orange pericarp orp*-888D: This mutant was probably orp1 and was already in one of the treatment parents thus forming an orp duplicate pair with either mn4 or cp3 one of which is likely an allele of orp2.