expression of aleurone-specific genes
--Walton C. Galinat
In the process of recombining the two-celled
pericarp from teosinte with the multiple layered aleurone from Coroico
in a sweet corn background, a faint blue color was detected. In addition
to the prime components of selection, the blue color was held onto in the
hope that it would be an easy tool to identify the multiple-layered segregants.
In fact, this has proven to be the case. As the number of aleurone layers
increased, there was a dosage effect on increases in the intensity of blueness.
Freehand sections through the kernels showed the blue was present in all
layers. It may be expected that other aleurone-specific genes will have
dosage effects in the multi-layered aleurone and, thereby, increase the
total output of their special phenotype. This dosage effect with increased
layering appears also to be manifest with genes for the bronze or orange
colored aleurone that is common in Coroico. The most primitive kernels
from Tehuacan had this same bronze-orange aleurone; identified as the race
Nal Tel, it may have been the distant ancestor of Coroico. The Tehuacan
kernels were not sectioned and Nal Tel is not known at present to have
multiple aleurone. It seems probable that the multi-layered condition evolved
under the eye and mind of the Guarany Indians. The aesthetic beauty of
these intensely orange ears with multi-layered aleurone was probably the
direct reason for their selection by the Guarany Indians. But the multiple
aleurone may also have other benefits not initially intended such as increased
protein in an opaque-2 background (Nelson and Chang, Crop Sci. 14:374,
1974) and a potential to cope with increased kernel size.
It is hoped that this stock with thin
pericarp and thick aleurone will not only result in new high quality sweet
corn but that it will also be useful in studies of gene action in the aleurone
and of the chemical improvement of the nutritive value of this digestible
layer or layers.
Seed of my blue multi-aleurone, thin
pericarp stock has already been supplied for research purposes to Dr. Prem
Chourey (Univ. of Fla., Gainesville) for studies of gene action and to
Dr. Victor Raboy (Montana State Univ., Bozeman) for studies of phytic acid.
The sweet corn inbred Illinois 677a
is reported by Dusty Rhodes to contain some Coroico germplasm. The inbred
has been important as a source of the se (sugary enhancer) gene.
It has only a single aleurone layer, unlike Coroico.
The combination of Ma and Tpe
such as occurs in Coroico with sh2 (shrunken) endosperm is a better
means to cope with the sh2 germination problems than the currently
used thick pericarp which gives poor eating quality.
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