Maize
Genetics Cooperation Newsletter 80. 2006.
inr1 and inr2 are loci with dominant alleles that suppress aleurone color in crosses to specific r1 haplotypes (Stinard and Sachs, J. Hered. 93:421‑428, 2002). To date, several dominant alleles of inr1 and inr2 have been isolated from diverse sources (Stinard, MNL 78:62-63 and MNL 79:46). In 2004 (MNL 78:62-63), we reported a putative inr1 allele that was isolated from an Fcu line obtained from Peter Peterson. Fcu-induced sectoring and putative Fcu revertant events confounded the linkage tests we performed with Inr1‑JD, but since then, an Inr*‑Fcu line free of Fcu has been constructed and subjected to linkage analysis. The linkage test was set up as follows: A line homozygous for Inr1‑JD and the responsive haplotype R1‑Randolph was crossed to a line homozygous for Inr*‑Fcu and the responsive haplotype R1‑ch(Stadler). F1 kernels were planted, and the resulting plants were crossed by a line homozygous for R1‑Randolph, without inhibitors. Kernels on the resulting ears were scored for pale vs. full aleurone color, and of 3,712 kernels examined, all were pale. Thus, no full color recombinants lacking both inhibitors were detected, and we calculate the map distance between Inr1‑JD and Inr*‑Fcu to be less than 0.054 � 0.038 centiMorgans. We conclude that these two factors are most likely allelic, and have renamed Inr*‑Fcu as Inr1‑Fcu.
As
reported previously (Stinard and Sachs, 2002), Inr1‑JD and Inr2‑JD were isolated from an open pollinated variety known
as John Deere, so named for its green aleurone color. We identified another green aleurone maize variety called
Oaxacan Green Corn in the collection of the Abundant Life Seed Foundation of
Port Townsend, Washington, obtained seeds of it, and subjected it to the same
analysis as John Deere, and found that it, too, carries two r1 haplotype-specific inhibitors of aleurone
color. So far, we have isolated
and characterized one of the inhibitors and found it to be most likely an
allele of inr2. Mapping crosses of this factor with Inr1‑JD showed independent segregation, but in mapping
crosses with Inr2‑JD
carried out in a homozygous R1‑Randolph background, we found no crossovers in a population
of 5,861 kernels, indicating a separation of less than 0.034 � 0.024 cM between
these two factors. We have named
this factor Inr2‑OGC. If the second factor turns out to be
allelic to inr1, then it seems
likely that Oaxacan Green Corn and John Deere are just independently maintained
isolates of the same open pollinated variety. Both lines have similar maturity and gross plant morphology
(cob color, ear shape and size, tassel branching, etc.).
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