University of Florida
The sweet corn “Silver Queen” contains two genes conditioning white seed
--L. C. Hannah and D. R.. McCarty
For a number of years, we have used the sugary sweet corn `Silver Queen' as a su tester. `Silver Queen' is a white sweet corn which is quite popular in Florida. In our initial series of testcrosses, all resulting kernels were yellow, indicative of a recessive white being carried by `Silver Queen'. However, during the past 6 to 7 years we have noted that testcross ears segregate approximately 1/2 yellow and 1/2 white. This occurred when several yellow lines were crossed onto `Silver Queen'. These results are consistent with two hypotheses: (1) Silver Queen now contains two alleles of one locus. One allele is a dominant white while the other is a recessive white. (2) There are now two genes in this hybrid which condition a white seed. `Silver Queen' is homozygous for a recessive white but heterozygous for a non-allelic dominant white.
To distinguish between these two possibilities, white plump seed were selected from a cross of yellow, sh2 corn “Florida Stay Sweet' by the su `Silver Queen'. Plants were grown, self-pollinated and yellow plump seed were selected. Nine plants derived from such seed produced, upon self-pollination, four progenies that segregated for white seed. Were there one locus conditioning white seed in Silver Queen, selection in the original cross for white seed would also have selected against the presence of the recessive white allele being present in the F1 seed. Thus yellow seed, derived from the F2, should have been homozygous for the yellow allele at this locus and should not have produced white seed in subsequent generations. The finding of segregation in 4 of the 9 F3 progenies clearly rules out the “one gene-two white allele” hypothesis.
We conclude that there exist two genes conditioning loss of carotenoid
pigmentation in `Silver Queen'. The cultivar is homozygous for a recessive
white and heterozygous for a non-allelic dominant white. If there is not
linkage between the two loci, we would have expected 6 of the 9 progeny
above to have segregated for white seed. The finding of 4 segregating progeny
is consistent with very loose or no linkage between these two genes.
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