LINKAGE BETWEEN SWEET-DEFECTIVE AND
SUGARY ENDOSPERM I N MAIZE
JOHN B. WENTZ
Iowa State College, Amw, Iowa
Received March 5, 1925
TABLE OF CONTENTS
PAGE
INTRODUCTION..................................................................
Additional data on the inheritance of sweet-defective.................................
Linkage between defective endosperm and sugary endosperm. ........................
SUMMARY .......................................................................
LITERATURE
CITED.. .............................................................
395
395
397
401
401
INTRODUCTION
I n the spring of 1922 Doctor E. W. LINDSTROM,
then a t the UNIVERSITY
WISCONSIN,
sent the writer some normal seed from a self-pollinated ear
of Golden Bantam sweet-corn which was segregating for a very distinct
type of defective endosperm. LINDSTROM
(1923) has since published data
which show that this character is inherited as a simple Mendelian recessive.
During the summer of 1922 a number of crosses were made between this
Golden Bantam strain and five different starchy strains. Ears resulting
from these crosses were planted in the spring of 1923 and a large number of
selfings made. The data presented in this paper are from these selfpollinated ears.
OF
ADDITIONAL DATA ON THE INHERITANCE OF SWEET-DEFECTIVE
From the original seed furnished by LINDSTROM,twenty-one plants
were grown to maturity. Of these twenty-one plants, sixteen were either
selfed or used in crosses which were selfed in the next generation. Of the
sixteen plants, twelve proved to be segregating for defective endosperm,
giving a ratio of 4 pure normal to 12 segregating ears, as compared with a
theoretical ratio of 5.33 to 10.67, assuming a simple monohybrid condition.
I n the spring of 1923 seed was planted from ten different crosses. All
of these crosses happened to be with pure starchy endosperm plants either
as female or male parents. Of these crosses all segregated for sugary
endosperm in the Fz generation as expected, and seven segregated for
defective endosperm as well as the sugary character. From the seven
,
GENETICS10: 395 Jl 1925
396
JOHX B. \YENTZ
crosses segregating for defective endosperm, a total of 160 selfed ears
was obtained. Of these 160 selfed ears, 91 were segregating for defective
endosperm. This gives a ratio of sixty-nine homozygous normal to ninetyone segregating ears, as compared with a theoretical ratio of 8 0 : 80.
Each of the 91 ears was shelled and the number of normal and defective
kernels counted.They gave a total of 30,952 kernels, of which 23,222
were normal and 7730 defective, as’compared with a theoretical ratio of
23,214 to 7738, based on a simple monohybrid condition. The data from
the selfed ears are presented in table 1, by r0ws.I Rows 37 and 38 are
from the same cross and the same is true of rows 109 and 110. In each of
these two cases the two rows were planted from different-colored seeds
on the same ear. Rows 94 and 194, and 137 and 191 are reciprocal crosses.
TABLE1
Data ott nornzal and defective eadosperm.
DFl”TION
NUMBER OF
ROW
BEGREGAT-
NUMBER
37
38
53
74
85
94
109
110
137
191
194
ING E.4RS
1
14
7
11
8
8
10
4
8
8
11
2
1
NORMAL
DEFFCTlVE
SEEDS
SEEDS
3290
1774
3160
2014
2147
2283
917
2228
2015
3010
384
1
1081
646
1089
70 1
529
792
265
801
711
1002
113
TOTAL
DEVIATION
1
4371
2420
4249
2715
2676
3075
1182
3029
2726
4012
49 7
1
11.7.5
41 .OO
26.75
22.25
140.00
21.25
30.50
43.75
29.50
1.oo
11.25
1
1
PROM 3 TO 1 RATIO
P.E.
19.31
14.36
19.04
15.21
15.11
16.20
10.04
16.08
15.25
18.50
6.51
I
1
D””P.E.
0.61
2.86
1.40
1.46
9.27
1.31
3.04
2.72
1.93
0.05
1.73
~ - _ _
~_
_ _
_
Total
Not including
No. 85
91 .
23,222
7730
30,952
8.00
51.35
1 I 1 1 1 1 1
83
21,075
I
7201
-l-1
-I
28,276
132.00
49.08
0.16
2.69
One very wide deviation from theoretical expectation is seen in row
85. This row exhibits such a wide deviation from the expected 3 : 1 ratio
that it obviously should be considered separately. A possible reason for
this behavior will be discussed later in the paper.
It so happens that the wide deviation in this row makes the deviation
from expectation in the grand total smaller than it should be if this row
1
Data for individua! ears are available.
397
SWEET-DEFECTIVE AND SUGARY ENDOSPERM IN MAIZE
had behaved in the normal way. Eliminating row 85 from the data, the
deviation divided by the probable error of the totalis 2.69. I n most of the
rows where the deviations were rather large there were too many defective
seeds. These deviations are probably due largely to improper classification
caused by the presence of other defective types in some of the ears. I n
order to give someidea of the amount of deviation of individual ears from
the theoretical 3 : 1 ratio,the maximum and minimum deviations of
individual ears within each row, expressedby thedeviation divided by the
probable error, are presented in table 2. Except for row 85, none of the
deviations are unreasonably large considering thetype
of character
studied.
TABLE2
Maximum and minimum deviations of individual ears in each row from a
3 :1 ratio of normal to defective endosperm.
R O W NUMBER
37
38
53
74
85
94
109
110
137
191
194
NUMBER OF
SEGREGATINGEARS
14
7
11
8
8
10
8
8
11
2
DEVIATION DIVIDED BY PROBABLE EBROR
Maxlmum
Minimum
3.52
3.95
3.50
1.55
7.05
3.00
0.18
0.74
0.00
0.09
0.40
0.49
0.62
0.92
0.79
0.43
0.05
2 .59
4.05
3.63
3.07
4
2.43
LINKAGE BETWEEN DEFECTIVE ENDOSPERM AND SUGARY ENDOSPERM
When the ears segregating for both defective and sugary endosperm
were harvested, it was noticed a t once that there were far too few normal
sugary seeds present. This suggested a linkage between defective and
sugary endosperm, although it was impossibleto tell which of the defective
seeds were sugary and which were starchy. It was necessary, therefore,
to study the material on the basis of a 9 : 3 : 4 phenotypic ratio.
In table 3 the observed data on the three classes of seeds are compared
with what would be expected on the basis of independent inheritance.
It may be seen a t a glance that the observed numbers deviate so far from
the expected 9 : 3 :4 ratio that independent inheritance can not be
assumed.
GENETICS10: J1
1925
398
JOHN B. WENTZ
TABLE
3
Contpurison o'j observed and expected numbers o j seeds on the basis o j independent
inheritance o j sugary and defective endosperm.
I
S,, De
BOW
St' de
S" D e
+
su de
NUMBEB
Observed
37
38
Expected
Observed
Expected
3222
1730
3083
1927
2117
2265
903
2 188
1992
2932
380
2458.7
1361.2
53 2390.0
74
1527.2
1505.2
1729.7
109 664.8
1703.8
137 1533.3
2256.7
279.5
68
44
22,739
17,410.5
483
5803.5
15,905.3
453
5301.8
85
94
110
191
194
77
87
30
18
14
40
23
78
4
Observed
819.6
453.7
796.7
509.1
501.7
576.6
221.6
567.9
511.1
Expected
1081
1092.8
646
605 .O
1089
1062.2
701
678.8
529
669.0
792
768.8
265
295.5
801
757.2
711
681.5
1002 752.2 1003.0
113
124.2
93.2
L
Tot a1
7730
i738.0
"
Not includirg
No. 85
I
20,622
i201
1
i069.0
The data in table 3 suggest a very close linkage between defective and
sugary endosperm. Since it is impossible to make backcrosses on puredefective plants it is necessary to determine the gametic ratios from the
Fzphenotypic ratios. CASTLE(1916) has published a table giving gametic
ratios for different F2 zygotic ratios. By comparing the data in table 3
with a table madeup in the same mannerCASTLE'S
as
it was determined by
inspection that the Fz phenotypic ratio a t hand fits the gametic ratio of
30 : 1 closer thanany other.This
is a crossover percentage of 3.23.
Table 4 shows the actual numbers observed in the F2 and the numbers
expected on the basis of a 30 : 1 gametic ratio, not including data from
row 85.
TABLE
4
Comparison o j observed and expected numbers on
the basis o j a gametic ratio of 30 :1.
I
Su De
Observed. . . . . . . . . .
Expected. . . . . . . . , , .
Deviation.. . . .
.TI
20,622.0
20,758.3
~
-136.3
X?= 3.40100
I
1I
I
D,
+ su de
7201 .O
453 .O
7069.0
448.7
+4.3
S. de
I
P = . 188012
+132.0
SWEET-DEFECTIVE
AND
399
SUGARY ENDOSPERM IN MAIZE
The fit of the observed with the calculated numbers in table 4 is only
fair. That this is due to the excess of defective seeds previously mentioned, is seen from table 5 where the theoretical numbers of sugary and
starchy seeds are calculated disregarding the defective seeds.
TABLE
5
Comparison of observed and expected numbers of starchy and sugary
seeds where the defective seeds are disregarded.
Su L's
S"
De
"
Observed. .....
Expected.. .....
Deviation.
453.0
445.9
20,622.0
20,629.1
....
-7.1
$7.1
This very close fit does not prove, however, that there is linkage between
sugaryand defective endosperm. There could have been some other
factor causing the small number of normal sugary seeds. Fortunately,
though, as previously mentioned, there were 69 ears in these same rows
whichwere not segregating for defectiveseeds. If the low number of
TABLE
6
Data on starchy and sugary endosperm, from ears not segregcuing
j m defective endosperm.
ROW
NUMBER
IUHBEB
01
iEGREGATING EARS
I
DEVIATION FROM
3 TO 1 RATIO
STARCHY
SEEDS
SUGARY
1446
2 194
1641
2605
1780
1764
2173
708
2139
462
721
560
903
316
600
741
241
712
1908
2915
2201
3508
......
.....
719
235
954
3.50
9.02
0.30
17,069
5491
22,560
149.OO
43.86
3.40
15,289
51 75
20,464
59.00
41.76
1.41
SEEDS
TOTAL
DEVIATION
PROBABLE
ERROX
P.E.
DEV.
"
"
37
38
53
74
85
94
109
110
137
191
194
5
9
6
11
7
7
8
3
9
0
4
....
...
2364
2914
949
2851
....
15.00
12.73
7.75
15.74
9.75
13.70
26.00
17.31
208.00 2096 13.39
9.00
14.19
12.50
15.74
9 .OO
3.75
15.60
0.75
1.28
0.49
0.71
1.so
15.53
0.63
0.79
0.42
0.05
....
"
Total
69
"
Not including
No. 85
62
GENETICS10: J1 1925
400
JOHK B. m’ENTZ
normal sugary seeds had been due to some factor other than the factor
causing defective seeds, then one would expect to find this same deficiency
of sugary seeds in these ears. The 69 ears were shelled and counted for
starchy and sugary seeds and the data tabulated in tables 6 and 7. The
number of sugary seeds shown by these tables gives, with the exception of
row 85, very close approximation to the normal 3 : 1 ratio; thus, we have
rather conclusive proof that the small number of normal sugary seeds on
the ears segregating for defective must have been due to a close linkage of
sugary and defective seeds.
TABLE
7
Maximz~mand minimum deviations of individual ears in
each row, for sugary endosperm.
ROW
NUMBER OF
NUMBERS
SEGREGATING EARS
D’EVIATION DIVIDED BY PROBABLE ERBOX
Maximum
37
38
53
74
85
94
109
110
137
191
194
5
9
6
11
7
7
S
3
9
0
4
1.80
2.90
2.54
3.36
8.42
2.45
2.20
1.73
2.43
Minimum
0.31
0.04
0.23
0.35
2.33
0.23
0.09
0.54
0.39
....
....
1.94
0.06
It will be recalled that row 85 in table 1 showed a marked deficiency of
defective seeds when compared with the numbers expected on the basis
of a 3 : 1 ratio. Of the seven selfed ears in this row not segregating for
defective seeds, only one had approximately the expected 25 percent of
defective seeds. The other six ears showed percentages ranging from 8.2
of this row was heterozygousfor some
to 16.4. Evidentlytheparent
factor besides the one causing defective seeds: which greatly reduced the
number of sugary seeds, and, since it has been shown that defective seeds
is linked with sugary endosperm, the percentage of defective seeds would
also be reduced.
Unpublished data of Professor R. A. EMERSON
show that when sugary endospermis crossed
with Rice pop-corn the number of sugary endosperm seeds in the F2 falls markedly short of the
expected 25 percent. The pedigree of row 85 was studied and was found to trace back through
several generations to one of Professor EMERSON’S
crosses involving Rice pop-corn.
SWEET-DEFECTIVE AND SUGARY ENDOSPERM IN X U Z E
401
SUMMARY
1. Additional data arepresented on the inheritance of LINDSTROM’S
sweet-defective endosperm in Golden Bantam sweet corn.
2. Linkage between this defective endosperm type and sugary endosperm is reported, with a crossover percentage of 3.2.
LITERATURE CITED
CASTLE,W. E., 1916 Tables of linkage intensities. Amer. Nat. 50: 575-576.
of maize. XIII. Endosperm defects, sweet
defective and flint defective. Jour. Heredity 14: 127-135.
LINDSTROM,
E. W., 1923 Heritable characters
GENETICS10: Jl 1925