Each of the 534 kernels was examined
visually (with an 8-power magnification hand lens when needed) in a search
for colorless sectors since it is known (M. G. Neuffer and W. F. Sheridan,
1980) that dek1 mutant embryos do not synthesize anthocyanin. The
dek1
mutation segregates in a normal three to one fashion on self-pollinated
ears. Therefore about half or about 267 of the kernels examined should
be heterozygous for the dek1 mutation. In their study, Poethig,
Coe, and Johri (1986) irradiated plants carrying the R-sc allele
(which conditions anthocyanin synthesis only at the periphery of the scutellum,
and is therefore less favorable material than that containing the R-scm2
allele) in searching for colorless sectors against a colored scutellum
background. These workers used x-rays to break chromosome arm 9S bearing
the C-I allele, the loss of which allowed pigment formation to occur.
Poethig and coworkers found six sectored embryos out of a total of 815
kernels examined of material given 500R of hard x-rays at 56 hours after
pollination. This is a frequency of 0.7 percent. If the same frequency
of sectors were expected in the +/dek1 embryos then two embryos
of the 267 presumed heterozygotes or two among the 534 total embryos examined
should have displayed a colorless sector of dek1 mutant tissue.
No embryos have been found that contain colorless sectors. These results
are limited by the small sample size but are suggestive either that mutant
sectors cannot survive in the competition for nutrients during early kernel
development or that the mutant sectors are not cell autonomous. It seems
most likely that the former suggestion or small sample size applies to
these results.
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