A DOMINANT LETHAL CHLOROPHYLL MUTATION IN 
MAIZE 1 
By J. H. Kempton 
Assistant Botanist , Office of Biophysical Investigations , Bureau of Plant Industry , 
United States Department of Agriculture 
There are two outstanding facts with 
respect to the large number of heritable 
variations found in maize: First, prac¬ 
tically all are degenerative with a lower 
survival value than normal plants, and 
second, they usually are recessive, be¬ 
ing carried from generation to genera¬ 
tion in latent form. These two facts 
bear a direct relation to each other, for 
if deleterious variations were not reces¬ 
sive they would be eliminated promptly 
from the stock at a rate proportional to 
their lower survival value. It seems 
clear, therefore, that the large number 
of recessive as compared with dominant 
variations is due largely to the fact that 
the recessive variations represent the 
accumulation of mutations through 
many generations, while the only domi¬ 
nant mutations found are those which 
have originated recently or which have 
no selective value. There is, of course, 
a gradual elimination of the recessive 
mutations also, the rate depending 
upon their productivity in a homo¬ 
zygous form, but this elimination is 
comparatively slow. 
Recently, the writer has had an ex¬ 
cellent illustration of the elimination 
of a dominant mutation. In a popu¬ 
lation of 50 plants of an F 2 between 
two varieties of maize, one of which 
had been inbred for eleven, the other 
seven, generations there appeared a 
single plant one-half of which was 
normal green in color, the other half 
being yellow, of a shade similar to the 
yellow seedling of Lindstrom. 2 
Neither parent of the cross from 
which this plant arose ever has pro¬ 
duced yellow saedlings, and none of the 
sister plants showed the slightest tend¬ 
ency in this direction. The plant as a 
whole was a perfect example of a sec¬ 
torial chimera. The chimeral nature 
appeared with the first leaf and ex¬ 
tended throughout the entire plant. 
One-half of each leaf as well as one-half 
of the tassel was yellow, the affected 
portion being on the same side of the 
plant in each case. This division was 
apparent even on the central spike, 
where all the spikelets on one side were 
yellow and those on the other green. 
Two upper tassel branches were similar 
to the central spike, but the other 
branches of the tassel were divided 
equally, being either all green or all 
yellow. In appearance, the plant re¬ 
sembled the chimera reported by Kha- 
dilkar 3 except that in the case he re¬ 
ported the affected half was variegated 
yellow and white instead of self-yellow. 
The plant was very weak and when 
mature was less than one-third the size 
of its normal sibs. The growth also 
was slower and the flowers matured 
about 10 days later than those of the 
normal plants. No ear was formed 
but pollen was produced abundantly. 
Pollen was collected separately from 
the self-yellow and the self-green 
branches and as self-fertilization was 
not possible the pollen from the two 
sorts of spikelets was applied to two 
sister plants in an unrelated progeny 
which had been self-fertilized for 13 
generations and which had never pro¬ 
duced either albino or yellow seedlings. 
Being inbred for such a long period, 
the resulting ears were not as large as 
could be desired, but 200 seedlings were 
grown from each, those having the 
green section of the chimera as a male 
parent giving only green seedlings while 
those with the yellow section of the chi¬ 
mera as a male parent gave 102 green 
and 98 yellow seedlings. This obviously 
is an approximation of the 1 : 1 ratio ex¬ 
pected if the yellow portion of the plant 
was heterozygous for a dominant factor 
for the yellow chlorophyll disorder. 
Most of the seedlings were grown out 
of doors in the ordinary manner but a 
few seeds were reserved for planting in 
greenhouse flats to provide a compari¬ 
son with seedlings raised from the self- 
pollinated green sibs which survived in 
the field culture. 
1 Received for publication July 29, 1924: Issued January, 1925. 
2 Lindstrom, E. W.— chlorophyll inheritance in maize. N. Y. Cornell Agr. Exp. Sta. Mem. 13, 
68 p., illus. 1918. 
3 Khadilkar, T. R— a sectorial chimera in maize. Jour. Heredity 12: 284-285. 1921. 
Journal of Agricultural Research, 
Washington, D. C. 
( 307 ) 
Vol. XXIX, No. 6 
Sept. 15, 1924 
Key No. G-409 
