John Deere green aleurone corn carries two R1-specific dominant inhibitors of aleurone color --Stinard, PS John Deere corn is a variety of novelty corn with green kernels (Sprague. 1994. MNL 68:105). In order to isolate the cause of the green pigmentation, we crossed the John Deere line to various colored aleurone stocks. We found that in crosses to stocks carrying specific alleles of R1 (members of the R1-d class and R1-ch), dominant inhibition of aleurone color occurred in a pattern similar to that found for Inhibitor of R1 (Inr1; MNL 73:89-90). After backcrossing the John Deere line to our W23 ACR conversion, which carries an R1 allele susceptible to inhibition, for several generations, a pattern emerged. Plants were obtained that produced ears giving a 15:1 ratio of colorless and pale to colored aleurone kernels, and whose outcrosses to our W23 ACR gave a 3:1 ratio of colorless and pale to colored aleurone kernels. These crosses are indicative of segregation for two dominant aleurone color inhibitors. Through several generations of self-pollination, we were able to obtain lines homozygous for each dominant inhibitor separately.

Allelism tests of these factors with Inr1 were done by crossing these separate lines to a homozygous Inr1-R line, and then crossing the resulting F1 by our W23 ACR line. One of the factors produced only colorless kernels in a population of thousands of kernels, indicating probable allelism. (There is always the remote possibility that the factor is not allelic to Inr1, but is instead extremely tightly linked to Inr1--these tests cannot rule out that possibility). The other factor produced ears segregating 3:1 for colorless to colored kernels in these crosses, indicating non-allelism with Inr1. We have given the second factor the temporary designation Inr*-JD until allelism with other known aleurone color factors can be ruled out. We are currently in the process of conducting linkage tests of Inr*-JD with a comprehensive set of wx1-marked A-A translocations.

We still do not have a precise explanation as to why John Deere corn is green. The R1 allele that is present in the John Deere line is apparently only weakly suppressed by the dominant color inhibitors. Perhaps the weak suppression of aleurone color occurring over the surface of yellow endosperm (John Deere is Y1 Y1) gives a green appearance through the combination of the light purple and yellow. Another possibility is the production of a unique anthocyanin pigment or some other chemical alteration in the aleurone cells that gives rise to a green color. Further analysis will need to be done in order to resolve this question.
 
 

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