Title: Corn varieties and hybrids and corn improvement
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Permanent Link: http://ufdc.ufl.edu/UF00027595/00001
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Title: Corn varieties and hybrids and corn improvement
Series Title: Corn varieties and hybrids and corn improvement
Physical Description: Book
Creator: Hull, Fred H.
Publisher: University of Florida Agricultural Experiment Station
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Bibliographic ID: UF00027595
Volume ID: VID00001
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Full Text
Bulletin 355

reuruary, L1.1.

-. -. ~-.c---r
7 __

- FREt) HULL. 1. 1) \\' RNTR, rd W\\ A. (.R ,LLR

John J. Tigert, M. A., LL.D., President
of the University3
Wilmon Newell, D.Sc., Directors
Harold Mowry, M. S. A., Asst. Dir.,
W. M. Fifield. M. S., Asst. to Director
J. Francis Cooper, M. S. A., Editors
Jefferson Thomas, Assistant Editors
Clyde Beale, A.B.J., Assistant Editors
Ida Keeling Cresap, Librarian
Ruby Newhall, Administrative Manager3
K. H. Graham, Business Manager8
Rachel McQuarrie, Accountant3
W. E. Stokes, M.S., Agronomist'
W. A. Leukel, Ph.D., Agronomist3
Fred H. Hull, Ph.D., Agronomist
G. E. Ritchey, M.S., Associate2
W. A. Carver, Ph.D., Associate
John P. Camp, M.S., Assistant
Roy E. Blaser. M.S.. Assistant
Fred A. Clark, B.S.A., Assistant
A. L. Shealy, D.V.M., Animal Indus-
R. B. Becker, Ph.D., Dairy Husba.dman3
g. L. Fouts, Ph.D., Dairy Technologist-
T. R. Freeman, Ph.D., Associate in Dairy
W. M. Neal, Ph.D., Asso. in An. Nutrition
D. A. Sanders, D.V.M., Veterinarian
M. W. Emmel, D.V.M., Veterinarian2
N. R. Mehrhof, M.Agr., Poultry Husbh.
W. G. Kirk, Ph.D., Asso. An. Husb.
D. J. Smith, B.S.A., Asst. An. Husb.s
P. T. Dix Arnold, M.S.A., Asst. Dairy
L. L. Rusoff, Ph. D., Asst. in An.
0. W. Anderson, M.S., Asst. Poultry
L. E. Mull, M.S., Asst. in Dairy Tech.
R. V. Allison, Ph.D., Chemist'
Gaylord M. Volk. M.S., Chemist
F. B. Smith, Ph.D., Microbiologists
C. E. Bell, Ph.D., Associate Chemist
H. W. Winsor, B.S.A., Assistant Chemist
J. Russell Henderson, M.S.A., Associates
L. H. Rogers, M.S., Asso. Biochemist
Richard A. Carrigan, B.S., Asst. Chemist
C. V. Noble, Ph.D., Agr. Economists 8
Zach Savage, M.S.A., Associate
A. H. Spurlock, M.S.A., Associate
Max E. Brunk, M.S., Assistant
Ouida D. Abbott, Ph.D., Home Econ-
Ruth Overstreet, R.N., Assistant
R. B. French, Ph.D., Asso. Chemist
J. R. Watson, A.M., Entomologist'
A. N. Tissot, Ph.D.. Associate
H. E. Bratley, M.S.A., Assistant
G. H. Blackmon, M.S.A., Horticulturist'
A. L. Stahl. Ph.D.. Associate
F. S. Jamison, Ph.D., Truck Hort.8
R. J. Wilmot, M.S.A., Fumigation
R. D. Dickey, M.S.A., Asst. Horticulturist
J. Carlton Cain, B.S.A., Asst. Hort.
Victor F. Nettles, M.S.A., Asst. Hort.
F. S. Lagasse, Ph.D., Asso. Horticulturists
H. M. Sell, Ph.D., Asso. Horticulturist'
W. B. Tisdale, Ph.D., Plant Pathologist' 8
George F. Weber, Ph.D., Plant Path.'
L. 0. Gratz, Ph.D., Plant Pathologist
Erdman West, M.S., Mycologist
Lillian E. Arnold, M.S., Asst. Botanist

H. P. Adair, Chairman, Jacksonville
W. M. Palmer. Ocala
R. H. Gore, Fort Lauderdale
N. B. Jordan, Quincy
T. T. Scott, Live Oak
J. T. Diamond, Secretary, Tallahassee

J. D. Warner, M.S., Agron. Acting in
R. R. Kinkaid, Ph.D., Asso. Plant Path.
Elliott Whitehurst, B.S.A., Assistant An.
Jesse Reeves, Asst. Agron., Tobacco
J. D. Warner, M.S., Agron. Acting in Chg.
John H. Jeffries, Asst. in Cit. Breeding
Chas. K. Clark. Ph.D.. Chemist
B. R. Fudge, Ph.D., Associate Chemist
W. L. Thompson. B.S., Associate
F. F. Cowart, Ph.D., Asso. Horticulturist
W. W. Lawless, B.S., Asst. Horticulturist
R. K. Voorhees, M.S., Asst. Plant Path.
J. R. Neller, Ph.D., Biochemist in Chg.
J. W. Wilson, Sc.D., Entomologist
F. D. Stevens, B.S., Sugarcane Agron.
Thomas Bregger, Ph.D., Sugarcane
Frederick Boyd, Ph.D., Asst. Agronomist
G. R. Townsend, Ph.D., Plant Pathologist
R. W. Kidder, M.S.,Asst. An. Husbandman
W. T. Forsee, Ph.D., Asso. Chemist
B. S. Clayton, B.S.C.E., Drainage En-
F. S. Andrews, Ph.D., Asso. Truck Hort.
Geo. D. Ruehle, Ph.D., Associate Plant
Pathologist Acting in Charge
S. J. Lynch, B.S.A., Asst. Horticulturist
W. F. Ward, M.S., Asst. An. Husbandman
in Charges

M. N. Walker, Ph.D., Plant Pathologist
in Charge
K. W. Loucks, M.S., Assistant Plant
Plant City
A. N. Brooks, Ph.D., Plant Pathologist
A. H. Eddins, Ph.D., Plant Pathologist
E. N. McCubbin, Ph.D., Asso. Truck
Samuel O. Hill, B.S., Asst. Entomologists
Jos. R. Beckenbach, Ph.D., Truck Horti-
culturist in Charge
David G. Kelbert, Asst. Plant Pathologist
R. W. Ruprecht, Ph.D., Chemist in
Charge, Celery Investigations
W. B. Shippy, Ph.D., Asso. Plant Path.
E. S. Ellison, Meteorologists
B. H. Moore, AB., Asst. Meteorologists

1Head of Department
'In cooperation with U. S.
3Cooperative, other divisions, U. of F.


Fred H. Hull, J. D. Warner and W. A. Carver

Yield Tests with Corn Varieties Improvement of Open-Pollinated
and Hybrids __ 4 Corn Varieties _- 31
Description of Corn Varieties and Origin and General View of Hybrid
Hybrids _..____.____.. 11 Corn 34
Characteristics of a Good Utility Development of Hybrid Corn 35
Type of Corn __... 21 Commercial Production of Hybrid
Corn Improvement __25 Seed Corn in Florida ___-- 43
Reproduction in Corn .__--_ 25 Use of Hybrid Seed Corn in Florida- 48
Control of Pollination with Corn- 29 Grading Seed Corn---- 48
Recommendations -- 49

Corn is grown in Florida primarily for grain production,
although small acreages are harvested as silage, and as roasting
ears for Northern markets. In the northern half of Florida corn,
as the principal grain crop, occupies a large proportion of the
acreage of cultivated land. Most of the crop is fed to livestock on
the farms where it is produced.
The climate of the corn growing region of Florida is generally
warm. Annual rainfall is 50 to 60 inches, most of which occurs
in June, July, and August. Rains in April and May are infrequent
and periods of two weeks or longer without rain occur nearly
every year in June and July. Such periods may be preceded and
followed by periods of almost daily rainfall.
The various soil types are found more often in their lighter
phases. Bacteria and other micro-organisms work almost continu-
ously throughout the year to destroy accumulations of vegetative
materials or humus in the soil. Light soils with low humus
content dry out quickly in dry periods. Soluble plant foods are
rapidly leached from them in rainy periods.
Destructive field insects and diseases over-winter easily and
find a long corn growing season in which they may work. Weevils
and other insects which attack the mature grain, and ear-rot
disease organisms, as well, are favored by a period of four to six
weeks of warm, rainy weather after the corn is fully mature.
The corn which is mature in July must stand in the field until
dry weather in September makes crib storage safe. Weevils may
continue working in the crib through most of the mild winter.

Florida Agricultural Experiment Station

Under conditions just described, Florida corn yields have
averaged about 10 bushels per acre for the past 10 years. The
average yield in the main corn belt states is about 30 bushels for
the same period. Most of the corn grown in Florida is interplanted
with peanuts, velvet beans, or cowpeas. It has been estimated
that the average acre of Florida corn should be credited with
about 500 pounds of peanuts or its equivalent in addition to the
10 bushels of corn. Nevertheless, corn yields in Florida are too
low. They may be increased by: (1) improved seed; (2) fertili-
zers; (3) better crop management practices; and (4) better soil
management practices.
The least expensive means of increasing corn yields is fre-
quently the use of improved seed. Improved seed corn is the main
theme of this bulletin, which reports results of variety tests and
breeding work done by the Florida Agricultural Experiment
Stations at Gainesville and Quincy in recent years. Results pre-
sented here apply more directly to the northern half of Florida
where most of the field corn is grown.

Yield tests with corn varieties have been conducted at
Gainesville each year since 1924 and at Quincy nearly every year
since 1927 by the Florida Agricultural Experiment Stations.
Many additional tests were run with farmers and county agents
in the period from 1928 to 1933. These latter tests were distributed
over the entire state, but most of them were in the northern half
where more corn is grown. Corn yield tests have also been con-
ducted by the Everglades Experiment Station at Belle Glade,
but no detailed summary of the results of those tests is included
Many varieties and farmers' strains of corn from Florida
and neighboring states have been included in the trials from time
to time. A few varieties from distant states and foreign countries
have also been included. Many have been discontinued because
of mediocre or poor performance. A few new varieties and new
hybrids have been tested only in the last few years. The total
number of corn varieties and hybrids entered in Experiment
Station trials since 1924 is approximately 100.
Nearly all entries in the State Experiment Station yield

Corn Varieties and Hybrids 5

tests have been varieties and hybrids of which seed was on the
market or available in commercial quantities. A new stock of seed
was obtained each year from the breeder or seed merchant. Most
entries have been included only at Gainesville for one or two
years before being entered in other tests. Many were discon-
tinued after this preliminary test at the main station because
they were obviously unsatisfactory.
Every test was located on the most uniform land available.
All entries in one test were planted on the same date and given
the same fertilizer and cultural treatment throughout. Tests in
cooperation with farmers and county agents were fertilized and
cultivated according to the farmers' regular practices. In most
cases the farmer's own seed corn was included as an additional
entry in the test on his farm.
Tests at Gainesville and Quincy for each of the past three
years have consisted of six separate plats of each variety and
hybrid entry. Earlier tests on the Experiment Station farms
consisted of three and four plats of each entry each year.
Tests on private farms consisted of only a single plat of
each kind of corn but were located on six or more farms over
the region each year. It is hardly possible to obtain consistent
results with less than three plats of each entry for a single year;
nor is it possible to obtain a satisfactory measure of a variety in
less than three years. Comparisons of crop yields made on ad-
jacent areas with no repetition are often very misleading because
of hidden differences in soil fertility.
Records have been taken on yield of sound corn in every test.
Additional records on weevily and rotten ears, lodging of the
stalk, number of ears per plant, average weight of ears, days from
planting to silking, shelling percent, height of plant, cob color,
etc. have been kept with many of the tests. Test plats were
usually harvested in September at the normal time except at
Gainesville, where harvest has been delayed from one to three
months each year. Delayed harvest allows more severe insect,
disease, and weather damage to develop and thus provides more
critical comparisons. Some years when weevil infestation was
light in August, a small amount of corn badly infested with
weevils was strewn in the field to provide a more satisfactory
determination of weevil resistance. Percent of weevily ears
recorded at Gainesville is therefore much higher than in other
tests or on farms in the Gainesville region.

Florida Agricultural Experiment Station

Results of corn yield tests have been released currently in
mimeographed circulars from the Experiment Station since
1924. Tabular summaries of results for the past five years are
presented in the following section. They seem to provide ample
support for recommendations given in this bulletin. Neverthe-
less, the records of earlier tests provided a wider perspective
view of the entire situation than that found in recent work.
They thus served very well to guide the breeding work de-
scribed in later sections.
Corn varieties included in earlier performance tests fall
mostly into two distinct groups. In the first group are native
varieties and farmers' strains which have mostly one-eared
plants. They are somewhat resistant to weevil infestation and
damage in that the ear is covered with a long, heavy, tight husk,
and kernels are smooth dent to flint in type. The second group
includes prolific varieties from neighboring states. These varieties
have shorter and looser husks. Kernels are soft in texture and
medium to rough dent. Percent of weevily ears ranges much high-
er in prolific varieties than in Florida varieties and the damage
to an infested ear of soft corn is much greater than to an infested
ear of hard corn, as every Florida corn grower knows. However,
yields of prolific varieties, almost without exception, ranged from
15 to 30 percent above yields of the best native varieties. It was
obvious from these results that the main objective in corn
breeding work should be a combination of prolificacy and high
yield with weevil resistance.
Comparisons of results from tests on private farms under
prevailing farm conditions with results obtained on the Experi-
ment Station farms under somewhat different conditions show:
1. Ranking of variety yields on private farms is generally
the same as on Experiment Station farms.
2. Ranking of variety yields in the northern half of the state
is generally the same in all sections of that region. There are
some exceptions.
3. Ranking of variety yields in the southern half of Florida,
particularly on muck lands, is likely to be quite different from
that found in the northern half of the state.
4. Ranking of variety yields on river and lake bottom muck
lands in upper peninsular Florida is generally the same as on the
farm of the Everglades Experiment Station at Belle Glade.

Corn Varieties and Hybrids

Results of yield and performance tests with corn varieties
and hybrids for the past five years at Gainesville and Quincy are
presented in Tables 1 and 2. These results are of interest because
they substantiate earlier results reported in the preceding section.
Main interest in them, however, centers on new varieties and
hybrids which could not be included in earlier tests.
Separate yield records for the five years are given in the first
five columns in each table with the five-year average in column
six. It will be noted that a good many entries did not occur in
every one of the five years. For that reason it has seemed desir-
able to adopt a special method for calculating the five-year
average. It would be unfair, for example, to make a straight
comparison between two varieties in the event that one was
included in only the best two years and the other in only the
poorest two years of the whole five years of testing. Five varieties
that were included every year were chosen as check varieties.
The average yield of the five checks was then calculated for
each year. Each yield record in the table was expressed as a per-
centage of the check yield for the given year. Percentage yields
of each variety were then added and the sum divided by the
number of years that variety was included. The average percent-
age yield of the variety was finally multiplied by the average
yield in bushels of the five check varieties for the whole five
years. Records on the other six characters listed in the tables
were also averaged by the same method. This method has been
used a number of times in summarizing similar situations with
records on field experiments and is believed to be quite satisfac-
tory for the purpose. An additional check was made, however,
by employing the same method to calculate average yields for
the past three years, 1938-'40. These three-year averages were
very similar to the five-year averages and have been omitted
from the tables.
A special entry in these tests is that known as Farmer Com-
posite. This is a representative mixed sample of corn grown on
farms in the northern half of Florida. It has been obtained by
collecting one or two ears from each of some 200 farms distributed
over the area. A fresh sample has been used each year to avoid
any effects of crossing the different types of corn found in the
composite sample. It is believed that the fairest and most direct
measure of the yield value of a corn variety is its yield by weight

Florida Agricultural Experiment Station

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Ave. Yield Ears per Average Percent Percent Percent Days
cre Percent Plant Weight Weevilly Rotten Lodged Planting
1940 1936-'40 Farmer2 Ear Ilbs. Ears at Ears3 Plants to Silking
Avefagel Composite Harvest'

38.1 31.7 39.4 35.0 121 1.8 0.36 19 5 58 90
6.6 41.8 28.4 42.7 36.0 124 2.0 .35 27 7 65 89
24.9 29.2 36.4 34.4 118 1.9 .36 39 10 56 88
26.9 29.5 48.7 36.6 126 2.9 .25 46 8 70 91
30.3 38.2 132 3.1 .23 34 8 84 91
40.8 35.1 121 1.8 .40 51 10 66 87
39.8 34,2 118 1.8 .38 79 9 53 83
S 35.0 24.9 36.9 22.2 33.5 30.5 105 1.8 .33 15 5 65 86
35.4 22.9 37.4 23.6 38.4 31.4 108 1.8 .34 17 6 63 88
32.6 23.3 31.9 29.0 100 1.4 .41 13 9 68 85
Flint ... 34.5 23.6 31.0 24.0 36.2 30.0 103 1.4 .42 15 6 72 86 C
38.9 27.5 34.2 118 1.6 .42 19 6 75 86
t -- omson -23.1 22.3 29.2 101 1.2 .45 14 6 68 89
lintThomson 25.9 32.2 30.2 104 1.1 .51 86 2 73 89
Woo --- Wh P 36.1 27.3 33.9 117 1.2 .55 19 6 55
28.7 25.5 88 1.1 .38 6 3 64
er Comosite2 ---. 32.0 23.6 32.1 22.6 34.3 29.0 100 1.3 .42 14 8 64 86
yellow Varieties
Florident Yellow ...... 39.1 27.1 41.4 29.6 40.9 35.7 123 1.9 0.36 22 6 52 90
Good Golden Prolific 36.5 23.6 41.0 25.7 35.7 32.4 112 1.7 .38 29 11 68 86
Hastings Yellow Prolific 26.8 41.9 34.9 120 2.3 .30 61 8 68 88
Cuban Yellow Flint .. .. 27.6 20.1 28.1 20.6 25.3 87 1.3 .38 9 5 68 86
Special Cuban Flint K.. 23.4 30.2 27.7 96 1.2 .44 10 7 75 86
Imp. Cuban Flint Thomson 22.5 34.1 28.8 99 1.3 .45 9 7 78 86
Erck Yellow Flint .....at... O b 29.6 22.4 27.3 22.9 27.1 94 1.4 .38 13 4 62 86
Wilson Yellow Dent ...... 27.7 19.8 25.3 87 1.2 .39 15 7 64
Lowman Yellow Dent .. 28.1 18.2 24.4 84 1.1 .45 42 11 59
Clovelly Yellow Dent ..... 30.9 23.3 29.0 100 1.2 .47 44 7 40 N
Strawberry 28.6 24.6 85 1.1 .42 94 10 42 75
Fla. W-1 ................. 47.8 33.6 47.4 41.6 143 2.1 0.38 7 3 52 90
Fla. W-1, 2nd generation 30.7 26.4 91 1.8 .29 12 6 49 92
Louisiana A-1030 -.._....--. 48.4 41.6 143 2.1 .38 26 6 49 86
Louisiana A-2509 -..-. __.......... 42.9 36.9 127 2.1 .34 41 7 56 89
Louisiana A-2909 --.....-._..... 42.2 36.3 125 2.3 .30 45 6 58 87
Wood Hybrid Golden
Prolific GA-1958 ..... 36.0 22.2 33.7 29.4 35.9 31.7 109 1.8 .37 50 10 58 82
Wood Hybrid White Prolific 27.0 24.1 39.6 33.2 114 1.6 .42 55 7 55 86
Wood Hybrid Red Cob
Prolific CG-2351 43.7 37.6 130 1.4 .52 87 10 58 85
Wood Hybrid Red Cob
Prolific CI-2353 ..-- 42.1 36.2 125 1.9 .38 39 7 63 89
Iowealth 4310-15E 15.0 19.6 68 1.3 .29 49 18 88
Towealth 12-6 .--- 7.9 12.7 44 1.0 .20 49 18 100
Iowealth 12-1015 --..... ..-. 10.1 13.2 46 1.1 .24 43 21 98 'O

1Calculation of corrected averages described on page 7.
2Farmer Composite described on page 7,
SAverage harvest date October 10.

Florida Agricultural Experiment Station

expressed as a percentage of Farmer Composite yield. Those
values are listed in column seven of the two tables.
The highest yield at both Gainesville and Quincy is that of
the new Experiment Station hybrid, Fla. W-1 (Florida White
Hybrid No. 1). This hybrid has about the same proportion of
weevily ears as the Farmer Composite. Commercial production
and use of Fla. W-1 seed is discussed in later sections.'Fla. W-1 is
the only hybrid entry that can be recommended now for general
use in Florida. Louisiana Hybrid A-1030 has made good records
at both Gainesville and Quincy in 1940, but it will be desirable
to test it one or two more years before drawing definite conclu-
sions as to its value in this state.
Among white varieties higher yields were obtained from
Florident White, Whatley Prolific, Hastings Prolific, and Kilgore
Red Cob Prolific. If weevily and rotten ears and lodging are also
taken into consideration, Florident White is probably the one to
be preferred. Florident White has more flinty kernels and better
husk covering than the others named above.
Somewhat lower yielding white varieties which are approxi-
mately equal or superior to the Farmer Composite in weevil
resistance are McIntosh, DuBose, Kilgore Improved Florida
Flint, and Munroe Little Cob. These last varieties may be stored
in slat or pole cribs without fumigation, as is the common farm
Among yellow varieties Florident Yellow is to be prefer
for high yield, resistance to lodging and fair resistance to weev
Maximum weevil resistance with some sacrifice of yield is f
in Cuban Yellow Flint, Special Cuban Flint, and Improved C
Many more out-of-state hybrids have been include
at Gainesville than are listed in Table 1. None of them
satisfactory resistance to weevils. Those from the m
states have the higher proportions of weevily ears.
Golden Prolific from Virginia is the only ou
which may be satisfactory for planting in F
week to 10 days earlier than native variety
9 percent more grain than the Farmer
would be satisfactory in small acreage
crop is made, before later varieties a
It is always very strongly re

Corn Varieties and Hybrids

saved from a crop of hybrid corn for planting the next year.
Theories supporting that recommendation are discussed in later
sections dealing with hybrid corn. Factual evidence is presented
in Tables 1 and 2 with records on the second generation of Fla.
W-1 listed immediately below records on the first generation.
Fla. W-1 yields in 1940 were 29.6 and 47.4 bushels per acre at
Gainesville and Quincy, respectively. Yields of the second genera-
tion in the same tests were 17.7 and 30.7 bushels per acre. These
figures are averages of six plats of each entry in each test. Yield
of the second generation of Fla. W-l is only 62 percent of the
yield of Fla. W-l. This illustrates the results to be expected if
even the nicest appearing ears of a crop of Fla. W-l should furnish
seed to plant another crop. Similar results have been obtained
wherever seed has been saved from a crop of hybrid corn.
Reductions in the second generation range from 15 to 40 percent.
It cannot be too strongly emphasized that saving seed from a
crop of hybrid corn will always produce disappointing results.
Descriptions and photographs of corn varieties and hybrids
Which are of particular interest in Florida at the present time
g are presented here. These descriptions must not be considered
exact, for the development of a corn plant depends on growing
S conditions fully as much as on breeding. The reader is referred
$ Tables 1 and 2 for records on the more important economic
S aracters of each variety. Following descriptions have been
S'gten to summarize and briefly amplify those records.
Sigin.-This is a first generation double cross hybrid of four
lines of corn developed by the Florida Experiment
I s'a is the only hybrid corn that the Florida Experiment
> .-,,released for commercial use.
0 ;Astics.--Prolific, two ears on nearly every stalk, up
1 1 | ared stalks at Gainesville; highest yielding corn
i | Gainesville and Quincy, 43 percent gain over
S : ng, tight husks, smooth dent kernel type,
S .. 2.a. m+,to that of Farmer Composite; strong root
d 0)1 Z U .t.; white seed; 50 percent red cobs, 50
W M o '^ l percent by weight 81.5; 79 pounds
M tx:; r b 72cloj gshel.
- : C ;5 PX r

Florida Agricultural Experiment Station

Fig. 1.-Fla. W-1. Upper, entire yield of
16-hill plat; 28 not weevily, 2 weevily, 5 rotten
ears. Lower left, show sample of 10 ears slip-
shucked, 10 ears clean shucked. Lower right,
typical plant.

i ;
4 !

.I ,

* .

Fig. 2.-Florident Yellow. Upper, entire yield
of 16-hill plat; 25 not weevily. 2 weevily, 4
rotten ears. Lower left, show sample of 10 ears
slip-shucked and 10 ears clean shucked. Lower
right, typical plant.

Corn Varieties and Hybrids



Florida Agricultural Experiment Station

Origin.-Bred by Florida Experiment Station-see page 31.
First released for commercial use in 1941.
Characteristics.-Two-eared; highest yielding yellow variety
in tests at Gainesville and Quincy, 20 percent gain over Farmer
Composite; long, tight husks on most ears, smooth or slightly
rough dent kernel type, weevil resistance approximately mid-
way between Farmer Composite and the well known variety
Whatley Prolific; very strong root system and stalk, least lodg-

I l

II i

Fig. 3. Flori-
dent White. Up-
per, entire yield of
16-hill plat; 21 not
weevily, 10 weev-
ily, 5 rotten ears.
Left, show sample
of 10 ears slip-
shucked and 10
ears clean shuck-

Corn Varieties and Hybrids

Fig. 4. Farmer Composite.
Upper, random sample of ears
from Florida farms in 1938; 41
white, 4 yellow, 1 red. Center,
entire yield of 16-hill plat; 12
not weevily, 3 weevily, no rot-
ten ears. Crop produced from
seed shown above. Lower, typi-
cal plant.

ing of any entry in tests at
Gainesville and Quincy, this
statement strongly support-
ed by observations on fields
of Florident corn; yellow
seed; 85 percent red cobs; 15
percent white cobs; shelling
percent by weight 79.5; 85
pounds slip-shucked corn
shell one bushel.
Origin.-Same as Florident
Yellow-see page 31. First
released for commercial use
in 1939.
ly same as Florident Yel-
low, except seed color is






Florida Agricultural Experiment Station

Origin.-A representative, mixed (not interbred) sample
of corn grown on Florida farms in the past five years-see
page 7. Much of the corn grown by Florida farmers has been
in their possession for a long time and is not known by varietal
names. There is some variation in details, but the general types
are similar. This corn may be known as Florida Old Field corn.
A search through early histories of Florida has discovered many
references to corn growing, but no mention of type. In recent
years at least there have been introductions of such varieties as
Whatley Prolific, Hastings Prolific, Cuban Yellow Flint, and
early white varieties grown for roasting ears. The Farmer Com-
posite contains some of these varieties and some slight mixtures
of them with the Old Field corn.
Characteristics.-Florida Old Field corn is mostly one-eared,

t, i ,

.. j J

I* i

Fig. 5.-McIntosh, Show sample of 10 ears slip-shucked and 10 ears
clean shucked.

Corn Varieties and Hybrids

medium yield; long, heavy, tight husks, smooth to slightly rough
dent kernel type, weevil resistance good; medium root system,
strong stalk, likely to lodge in summer and fall storms; white
seed; Florida Old Field corn has white cobs, but about 15 percent
red cobs appeared in the Farmer Composite; shelling percent of
Farmer Composite by weight 81.5; 89 pounds slip-shucked corn
shell one-bushel.
Origin.-The Reverend W. H. McIntosh, Bonifay, Florida,
began growing this corn in 1908. He has selected seed from the
field with special attention to plant type.
Characteristics.-90 percent 2-eared, 10 percent 1-eared
plants, yield gain over Farmer Composite 11 percent at Gaines-
ville, 5 percent at Quincy; long, tight husks, smooth dent kernel
type, weevil resistance equal to that of Farmer Composite;
medium root system, medium stalk, more likely to lodge than
Farmer Composite; white seed; white cob; shelling percent by
weight 83; 83 pounds slip-shucked corn shell one bushel.
Origin.-W. R. DuBose, Lake Butler, Florida, and his father
have grown this variety for many years. Seed has been selected
from two-eared plants in the field since 1934.
Characteristics.-45 percent 2-eared, 55 2-eared 1-eared plants,
yield equal to Farmer Composite; long, heavy, tight husks,
smooth dent kernel type, weevil resistance slightly better than
in Farmer Composite; medium root system, medium stalk, lodges
more than Farmer Composite; white seed; white cob; shelling per-
cent by weight 81; 89 pounds slip-shucked corn shell one bushel.

Fig. 6.-DuBose. Show sample.

Florida Agricultural Experiment Station

i A -


Fig. 7.-Cuban Yellow Flint.
Show sample and typical plant.

Origin.-Native corn of
Cuba. Introductions h a v e
been made from Cuba into
Florida many times. The
entries listed in Tables 1
and 2 as Cuban Yellow
Flint and Special C u b a n
Flint were obtained from
the Kilgore Seed Company,
Plant City, Florida. Im-
proved Cuban Flint was ob-
tained from W. H. Thom-
son, Lloyd, Florida.
Characteristics. 20 per-
cent 2-eared, 80 percent 1-
eared plants, yields slightly
below Farmer Composite;
long, tight, heavy and very
tough husks, true flint kern-
el type, weevil resistance
very good, 60 percent as
many weevily ears as in
Farmer Composite; medium
to weak root system and
stalk, more likely to lodge
than Farmer Composite;
lemon to orange yellow
seed, few reddish yellow;
5 percent red, 95 percent

*.4- L*tariv




Corn Varieties and Hybrids

Fig. 8. Whatley Prolific.
Upper, entire yield of 16-hill
plat; 17 not weevily, 16 wee-
vily, 3 rotten ears. Lower, typ-
ical plant.

white cobs; matures 3 to 5
days earlier than native
Florida corn; shelling per-
cent by weight 80;87
pounds slip shucked corn
shell one bushel.

Origin. Seed obtained
from What 1 e y Brothers,
Helena, Georgia.
Characteristics. Two-
eared, yield gain over Far-
mer Composite 17 percent
at Gainesville, 24 percent at
Quincy; husks often short
and loose, rough dent kern-
el type, weevil resistance
much below Farmer Com-
posite, but best of out-of-
state prolific varieties; me-

f t-

I I o

u. r 0
\- t


Florida Agricultural Experiment Station

dium root system and stalk, more likely to lodge than Farmer
Composite; white seed, red cob; shelling percent by weight 81;
86 pounds slip-shucked corn shell one bushel.

Fig. 9.-Wood Hybrid Golden Prolific. Entire yield of 16-hill plat;
5 not weevily, 22 weevily, and 1 rotten ears.
Origin.-Seed obtained from T. W. Wood and Sons, Rich-
mond, Virginia.
Characteristics.-75 percent 2-eared, 25 percent 1-eared
plants, yield gain over Farmer Composite 10 percent; short, loose
husks, smooth or slightly rough dent type kernels, weevil resist-
ance poor; medium root system, short, small stalk, slightly more
likely to lodge than Farmer Composite; yellow seed; white cob;
shelling percent by weight 79; 80 pounds slip-shucked corn shell
one bushel.
Origin.-Seed lots of various pedigrees obtained from com-
mercial seed companies and Experiment Stations of states in the
main corn belt.

Corn Varieties and Hybrids

Characteristics.-One-eared, yields 10 to 50 percent below
Farmer Composite; short husks, dent type kernels, weevil re-
sistance very poor; medium root system, small slender plants.
Very poorly suited for planting in Florida.

Fig. 10.-Typical plant of an
Iowa double cross hybrid corn
grown at Gainesville, Florida. The
ear projects through the husk

A good variety of field corn
for general use in Florida:
1. Produces high yields.
2. Has strong resistance to
damage by insects, diseases, and
adverse weather.
3. Has good quality and ap-
4. Is well suited to common
feeding practices.
Many characteristics of the
corn plant which determine the
above points are inter-depend-
ent. Some of them are antagonis-
tic, making compromises nec-
essary in choosing an ideal type.
It is thus hardly possible to dis-
cuss each characteristic separate-
ly. The main characteristics of a
good utility type are listed first,
with brief discussions of what
may be controversial points giv-
en afterwards.
Characteristics of a good utili-
ty type of field corn in Florida
1. Two ears of equal size on
each plant, with no third ear.
2. Ears large, strongly at-
tached, hanging down when ma-
3. No evidence of disease on
plant or ear.

22 Florida Agricultural Experiment Station
4. Husks long, heavy and tight at the tip.
5. Stalk medium height, strong.
6. Root system extensive, many branches.
7. Kernels of smooth dent type.
8. Husked ear with 14 to 18 straight rows of kernels, cylin-
drical (not tapering) in shape.
Corn yield tests in the Southeastern United States have
consistently shown a marked gain in yield for prolific varieties
over one-eared varieties. Most of the gain is between one-eared
and two-eared types. A third ear does not provide much addi-
tional advantage except where total yields are exceptionally high.
Yield tests at Gainesville and Quincy with several hundred hy-
brids ranging from one-
Seared to four-eared types
f 8 have supported the above
statements in general. Some
7 of the highest yields were
obtained from two-eared hy-
Prolific corn (Figure 11)
is objectionable because of
5 t the greater difficulty of
S-- handling a larger number of
smaller ears. Small ear size
does not provide the best ap-
pearance. The difference in
ear size between one-eared
and two-eared corn is rough-
ly illustrated in Figure 12.
Where ear-worm infesta-
4 tions are likely to be heavy,
fewer and larger ears are
S-. desirable to reduce total
Sworm damage, because only
one ear-worm develops on
0 the tip of one ear. On the
other hand, husk extension
to reduce damage by both
SH ear-worms and weevils is
more easily obtained with a
larger number of smaller
Fig. 11.-A prolific corn plant with ears.
seven ears.

Corn Varieties and Hybrids

_-.' ,'- . . . ... .

Fig. 12.-Comparison of ear size of two-eared corn (top row) and
one-eared corn (bottom row).
When all factors are considered, two-eared corn seems to
be the more suitable type for average farm conditions in Florida.
The two good sized ears should be strongly attached to the
stalk to prevent dropping off before harvest. They should be
hung low on the stalk and on opposite sides to obtain balance.
The shank should have sufficient length and elasticity to allow
the mature ear to droop or hang down to avoid catching rain.
water and thus avoid ear rot.
A tight husk extension of two inches or more beyond the
tip of the ear often prevents infestation by weevils in the field
from the time when corn is mature in July until it is harvested
in September. This protection is continued in storage of slip-
shucked or snapped corn. Ear-worms usually enter the ear of
corn through the silk channel at the tip of the ear. The ear-
worm moth prefers to lay eggs on corn silk. Where husk ex-
tension is long, the ear-worm feeds on corn silk and eats its way

Florida Agricultural Experiment Station

down to the ear. It is often full-sized, or nearly so, ready to cut
through the husk, and drop to the ground for pupation by the
time it reaches the ear of long-husked corn. With short-husked
corn the young ear-worm begins eating on the kernels as soon
as it has hatched.
It is much more difficult to obtain maximum development
of ear size and yield with long-husked than with short-husked
corn. Husk extension and ear size are antagonistic in some de-
gree. Nevertheless, a tight husk extension of two inches or more
beyond the ear of corn is necessary to provide adequate pro-
tection against insect damage in Florida.
The corn plant which has a strong, sturdy stalk and an ex-
tensive root system is presumably better able to produce well
developed ears. In Florida the crop must be kept off of the
ground in the field through six to eight weeks of warm rainy
weather after it is mature. Frequently a heavy crop of velvet
bean vines must also be supported by the corn stalk. A strong
stalk, supported by a strong root system, and resistant to rotting
long after maturity is thus necessary.
All classes of corn from rough dent, which is quite soft, to
true flint, which is very hard, are grown in Florida, but smooth
dent, which is a medium type, is most common. Weevil damage
is usually more severe on the softer types, although weevils
do live in the flintiest of corn. Some classes of livestock are not
able to utilize flint corn efficiently unless it is ground before
feeding. Here again a compromise is made in choosing the medi-
um hard smooth dent for the general utility type.
Most fancy points which have been stressed in show card
scoring of ear corn have little or nothing to do with utility.
Straight, even rows of kernels make for finer appearance. A thick
ear with 20 or more rows of kernels dries out slowly and is more
likely to rot than a more slender and longer ear. A small cob
with a deep covering of kernels is usually considered an indica-
tion of high shelling percent. Great importance is frequently
attached to shelling percent. However, records on many varieties
of corn in tests conducted by the Florida Experiment Station in
past years show no appreciable differences in shelling percent
by weight. The average shelling percent for all varieties is ap-
proximately 81 percent.

Corn Varieties and Hybrids

For many years the only known method of improving corn
was selection of the best appearing ears each year to seed the
next crop. As a result of work done by agricultural experiment
stations and similar agencies during the past 50 years, hybrid
corn has recently become very popular, especially in the main
corn belt states. In those states corn improvement now means
simply the development of better hybrids.
In Florida hybrid corn is still in the experimental stage.
Results shown herein indicate that adapted hybrid corn may be
more profitably grown than ordinary varieties under many con-
ditions found in the state. Nevertheless, under some conditions
ordinary varieties of corn are likely to be grown for many years
yet to come. Breeding work with corn being done by the Florida
Experiment Station includes development of new hybrids and
further improvement of the Florident varieties by methods com-
monly recommended for the improvement of ordinary varieties
of corn.
The two methods of breeding are described below after
brief discussions of the reproduction process and methods of
controlling pollination in corn.
Some knowledge of the reproductive process in corn and how
it compares with reproductive processes in other plants is neces-
sary for a full understanding of the various breeding practices.
Reproduction in plants by true seeds seems to be funda-
mentally the same sexual process as is found in the higher ani-
mals. The essential feature is a union of two especially prepared
germ cells, the egg and sperm, to form the fertilized egg, which
by repeated cell divisions grows and becomes a new plant. Egg
cells are formed in female organs of the flower. Sperm cells are
formed within pollen grains in male organs of the flower.
When a pollen grain is lodged on the receptive stigma or female
part of the flower, a small tube grows from the pollen grain
into the stigma and down to the ovary. The sperm cell passes
along the pollen tube to the egg. A single strand of corn silk, the
receptive part of the female corn flower, with pollen grains and
pollen tubes is shown highly magnified in Figure 13.
Many plants have both female and male organs within the
same flower, while others have only one sex on a single plant.

Florida Agricultural Experiment Station

In the latter instance each plant has either all male flowers or
all female flowers. Corn is inter-
mediate with female flowers on the
ear shoot and male flowers on the
tassel, Figure 14. Both sexes are
found on the same plant but at sep-
arate locations.
Pollen may fertilize the same
flower in which it was produced,
or another flower on the same
plant. In either case the process is 'i
known as self-fertilization or self-
pollination. When pollen fertilizes
a flower on some other plant the i
process is called cross-pollination.
Corn pollen is light and dry. It
floats easily in the air and may be Fig. 13.-Single strand of corn
carried long distances by wind. silk and grains of pollen; tiny
tubes have grown out of the pol-
Corn pollen is also carried by bees len grains into small hairs on
and other insects which collect it the silk. Magnified 500 times.
for food. Corn is mostly cross-pollinated as are some other spe-
cies, under ordinary field conditions more than 90 percent of
the pollen functioning on the silks of a corn plant coming from
other surrounding plants. Peanuts, oats, wheat, and some other
plants are largely self-pollinated. Flowers of these plants con-
tain both female and male organs and are usually fertilized by
their own pollen. In the peanut there is less than 1 percent of
cross-pollination. Intermediate types are grain sorghums and
alfalfa, in which self- and cross-pollinations occur with about
the same frequency.
It is clear that a high degree of cross-pollination or cross-
breeding such as is the rule with corn will result in a broad an-
cestry. All seeds on one ear of corn have the same mother plant
but many sires are represented in surrounding plants. Continu-
ation of cross-pollination leads to variability rather than uni-
formity in hereditary makeup. If the seeds of a single ear of
corn are sown in a separate row, the resulting plants will be of
various types. If, however, the seeds of a single peanut plant are
sown in a separate row, the plants will appear nearly identical
in type. This uniformity in the latter instance is attributed to the
close breeding practice of the peanut which causes its ancestry
to be very narrow, only one ancestor to each generation. A corn

Corn Varieties and Hybrids

Fig. 14. Above, branch of i' "B
corn tassel, the male flower
head. Flowers on upper part of
branch opened and shed pollen
preceding day, mid-third flo. -
ers open and shedding pollen,
lower third flowers will open
next day. Right, ear shoot of
corn, the female flower head,
with husks removed. Each
strand of silk is attached to a' '
single female flower.

plant, on the other hand, is likely to have an increasing number
of different ancestors to each preceding generation-two par-
ents, four grandparents, eight great-grandparents, etc.
With each cycle of sexual reproduction there is a reshuffling
or reassortment of the hereditary factors which determine plant
type. If ancestry is narrow because of close breeding, there is
not much diversity among the hereditary factors and the reshuf-
fling occurring with sexual reproduction does not lead to much
variability. If ancestry is broad and cross-breeding is the rule,
as in the corn plant, there is much diversity of hereditary factors.
A new and wide array of types appears every generation. Uni-
formity of superior type has been obtained by the plant breeder
with cotton, rye, and sunflowers by artificially enforced close
breeding. Close breeding which is in fact inbreeding has been

t. AI

Florida Agricultural Experiment Station


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Corn Varieties and Hybrids

found to weaken corn plants to the extent that it must be care-
fully avoided or circumvented.
Many plants are propagated from vegetative buds found on
stem cuttings, tubers, bulbs, corms, etc. The process involved
here in each case is non-sexual. There is no reshuffling of heredi-
tary factors. Progeny from a mother plant by vegetative propa-
gation are identical in hereditary makeup, regardless of the
breadth of ancestry back of the mother plant. Where vegetative
propagation is possible the plant breeder's job is greatly simpli-
fied. It is only necessary to find a superior plant. The identical
type may then be reproduced at will and in quantity. Vegetative
propagation of corn is unfortunately not possible by any means
known at present.
Control of pollination in corn may be done by hand or in
isolated plots. The process of hand pollination as practiced at
the Florida Experiment Station is shown in Figure 15. A white
glassine or parchment paper bag is pulled down over the ear
shoot before any silks have appeared and become pollinated.
Usually about two inches of the husk is cut off with a sharp
knife to hasten emergence of all of the silks. When silk has
emerged on the second day or later it may be seen through the
partially transparent bag. A suitable tassel which has begun to
shed pollen is then covered with a large bag made of heavy
brown paper. Note the tassel branch in Figure 14 upper; the
flowers near the tip had shed pollen the previous day, those at
the middle were shedding when photographed, and those on the
lower end of the branch would probably shed pollen the following
day. The bag is folded over and held tightly at the base of the
tassel with a paper clip. Any time the following day, in the ab-
sence of moisture from rain or dew, the pollen plant is pulled
over part way, the bag loosened and the tassel shaken lightly in
the bag. The bag, with the mouth kept closed as tight as possible,
is then carried to the silks. The operation of hand pollination
is shown in Figure 15 center. After pollen is poured over the
silks, the pollen bag is clipped over the ear and around the stalk
to prevent out-pollination. In practice, removing the shoot bag,
dumping the pollen, and covering again with the pollen bag are
done in rapid succession to avoid contamination with stray
pollen likely to be floating in the air. By this method about
10,000 ear shoots are pollinated each year at the Florida Station

Florida Agricultural Experiment Station

by three men working through a period of six weeks with two or
three extra helpers in the mid two weeks rush period.
Pollination control on a more extensive scale is done in iso-
lated detasseling plots. This method is used mostly for the pur-
pose of producing single and double cross seed in commercial
production of hybrid seed corn. Only one pollen parent may be
used in a plot, but there may be many seed parents. The pollen
parent is planted in every third, fourth, or fifth row in the field
and seed parents in the rows between. Tassels are pulled from

Fig. 16.-A detasseling plot of corn, making the double cross hybrid
Fla. W-l, Florida Experiment Station. The pollen parent is planted in
every fifth row, the seed parent in the four intervening rows. Tassels
were pulled from the seed rows before they had shed any pollen.
the seed plants before they shed pollen-all pollen in the field
then comes from the one pollen or sire parent strain. A detassel-
ing plot making Fla. W-l seed on the Experiment Station Farm
is shown in Figure 16, with most of the detasseling completed.
Tassels must be pulled every day for a period of a week to 10
day. Finally, suckers and a few late plants in the seed rows may
be broken off or topped with a knife to complete the job. De-
tasseling plots should be separated from other growing corn,
including sweet corn, by at least one-eighth mile (40 rods). Bar-
riers of trees are desirable. A few extra rows of the pollen pa-
rent on each side of the plot, especially the windward side, will
be valuable in preventing out-pollination because of the greater
supply of the right pollen. A plentiful supply of the right pollen

Corn Varieties and Hybrids

in both hand work and in detasseling plots is always the best
safeguard against out-pollination.
Various methods of improving corn varieties or developing
new varieties of improved type have been tried by agricultural
experiment stations in the period beginning about 1890. By 1920
or 1925 it was generally agreed that none of the newer methods
had produced substantially better corn than had the old practice
of mass selection.
Mass selection involves simply selection of better appearing
ears or plants to supply seed for the next planting. Selected ears
are shelled and mixed en masse, hence the name mass selection.
The breeding stock is kept as pure as possible by avoiding mix-
tures with stray pollen from other kinds of corn. Mass selection
has been frequently preceded by an intentional or accidental cross
of two or more different types of corn.
Some notable Florida corn varieties developed by mass se-
lection are DuBose, McIntosh, Tisdale, Smith, Blitch Red Cob,
Kilgore Red Cob Prolific, Wilson Yellow Dent, Petree Gold
Standard, and Erck Yellow Flint. New additions to the list are
Florident White and Florident Yellow. Both Florident varieties
came from a single foundation stock which was made up on
the Experiment Station farm at Gainesville in 1932 and 1933. A
number of test crosses of inbred lines and varieties with Whatley
Prolific were grown under comparable conditions and four of
the better ones were chosen for inclusion with Whatley in the
new variety. Two were the varieties Cuban Yellow Flint and
Wilson Yellow Dent, and two were inbred lines, one of which
(5-27) came directly from Wilson Yellow Dent. The other inbred
line (B12-8-4) came from an outcross in Whatley Prolific but was
yellow flint type. Each of the four crosses was separately crossed
back to Whatley Prolific in 1933 and seeds of the four back-
crosses were mixed mechanically to form the foundation stock
of Florident. Florident ancestry is theoretically 78 percent What-
ley Prolific, with the other 22 percent coming mostly from Cu-
ban Yellow Flint and Wilson Yellow Dent.
The Florident stock was planted on the North Florida Ex-
periment Station farm at Quincy in 1934 in an isolated plot. It
has been grown there every year to the present time with
mass selection of seed in the field each fall. Main points of se-
lection have been: (1) Two large ears of equal size on each plant

Florida Agricultural Experiment Station

with no third ear (both ears used for seed); (2) strong, stocky
plants standing straight; (3) heavy, tight husks extending two
inches or more beyond the tip of the ear for protection against
weevils; (4) smooth, semi-flint kernel type; (5) freedom from
any indication of disease on the ear and stalk; (6) straight, even
rows of kernels and generally fine appearance of the ear.
The original stock of Florident was mixed yellow and white.
In the fall of 1936 the selected seed lot, after shelling, was sep-
arated into three groups, white, pale yellow and strong yellow
kernels. White and strong yellow were planted separately in iso-
lated plots. The crop from white seed was mostly white with a
few pale yellow kernels. After another year for increase and fur-
ther selection the white lot was distributed as Florident White to
farmers and seedsmen in the spring of 1939. The first crop from
strong yellow seeds contained many white and pale yellow as well
as strong yellow kernels. Selection of strong yellow seeds for
planting was continued two additional years before Florident Yel-
low was considered ready for distribution in 1941.
Whatley Prolific was used in the foundation Florident stock
because, as reported herein, it had been proven to be high yield-
ing over a wide range of corn growing conditions found in the
state. Furthermore, Whatley and varieties derived from Whatley
have made the best yield records in neighboring regions in the
states of Alabama, Georgia and South Carolina. Wilson Yellow
Dent, Cuban Yellow Flint, and the two inbred lines were in-
cluded primarily to bring in the best weevil resistance available.
They also provided yellow color. Inclusion of four strains besides
Whatley provided broad ancestry of the foundation stock. The
high proportion of Whatley ancestry (78 percent) was believed
desirable to increase chances of recovering the consistently high
yield performance of Whatley under various growing conditions.
Stating it another way, improvement of yield by mass selection
methods was thought to be more difficult than improvement of
weevil resistance, hence the larger proportion of high yield an-
cestry than of weevil resistant ancestry in the foundation stock.
Records on Florident corn at the Main and North Florida
Stations for the six years 1935-1940 show that yield began about
15 percent below that of Whatley. It rose rapidly at first, but the
increase has been less each year. The yield curve based on the
first six years indicates that with the present methods of se-
lection Florident yield is leveling off at a maximum slightly
above Whatley Prolific yield. During the same period yield rela-

Corn Varieties and Hybrids

tions between Whatley, Farmer Composite, and several standard
varieties have shown no significant variation. Prolificacy of
Florident expressed as percent of two-eared plants where What-
ley produced two ears for every plant began at 87 percent and
rose at a uniform rate to 96 percent in 1940. No records have
been kept of the relative size of first and second ears, but it has
been observed that size of second ears has shown marked im-
provement. Improvement of yield has been obtained for the
most part by increasing percentage of two-eared plants and size
of the second ear. The goal of two equal-sized ears on each plant
has been nearly reached and, as the yield curve shows, no further
rapid improvement of yield may be expected with present meth-
ods. Further improvement of yield will depend upon parallel
increase of the weights of both ears together for the most part.
Yield does not seem to be easily improved by selection after the
goal of two ears of equal size on each plant has been reached.
Percent weevily ears in the original Florident stock was
mid-way between Whatley and the Farmer Composite. It has
shown no significant change during six years of selecting husk
protection. This failure may be partly due to a counter effect
from selection for longer ears. Ears of Florident are longer than
the ears of Whatley Prolific, as may be seen by comparing Fig-
ures 1 and 2 with Figure 5. Flintiness of kernels has shown
marked increase in the six years of selection on Florident.
More rapid improvement of Florident corn might possibly
be obtained by introducing small proportions of other strains or
varieties that are particularly strong where Florident is weak.
Other breeding plans might be tried concurrently with mass
selection. The writers believe, however, that any extra effort
beyond straight mass selection will be more profitably expended
in the development of better hybrid corn. The next logical step
in the improvement of Florident is very probably the develop-
ment of a double cross hybrid of inbred lines derived from
Florident. That work has been in progress since 1938.
It is intended that mass field selection of both Florident
Yellow and Florident White, as outlined above, shall be contin-
ued indefinitely on the farm of the North Florida Experiment
Station. Growers of Florident corn who do not practice field
selection of seed will do well to obtain a fresh stock every few
years to maintain prolificacy and yield.
Where native varieties and farmers' strains which produce
many one-eared plants are continued, it will almost certainly be

Florida Agricultural Experiment Station

profitable to select seed from two-eared plants in the field. Both
ears are equally valuable for seed and both should be taken to
increase selection intensity. Maximum selection intensity de-
pends upon the average number of seeds from each plant which
grow into mature plants in the next generation. Under some
conditions each selected plant may produce 1,000 daughter plants.
Under other conditions the number of daughter plants may be
decreased to 500. Progress under the first conditions may be
twice as rapid as in the second case. In either case selection is
enforced only on the female side, since the pollen is a random
mixture from every plant in the field. Selection intensity with
mass selection of corn can never be very strong. All reasonable
care should be taken to keep it as high as possible by saving
seed from the smallest fraction of the best plants. The number
of selected plants should not be less than 10 if the weakening
effect of inbreeding is to be avoided. Any effort to select on the
male side by detasseling poor plants or otherwise is not recom-
Development of hybrid corn began about 1900 when sev-
eral men started making controlled hand pollinations. In 1908
Dr. G. H. Shull of the Carnegie Institution reported that he had
produced inbred lines of corn by applying pollen to silks of the
same plant and excluding other pollen. The seeds thus produced
on one plant were sown in a separate row and self-pollination
was repeated. By breeding from only one parent plant each
generation, a highly inbred line was produced. All inbred lines
so far developed have been much weaker than the parent stock,
but very uniform in contrast with open-pollinated corn. As ,Dr.
Shull reported, the first generation cross of inbred lines is also
very uniform and much more vigorous than the inbred lines.
Some hybrids are markedly superior to the parent, open-pollinat-
ed stock. When a good hybrid is discovered, its seed may be pro-
duced in commercial quantities year after year by recrossing the
parent inbred lines. Inbred lines after four to six successive self-
pollinations remain constant or breed true generation after gen-
eration because their heriditary makeup is fixed by the inbreed-
ing process. For the same reason, the result of crossing two
inbred lines is always the same.
(The front cover picture shows four 10-ear samples of uni-
form corn from 50 plants of an experimental single cross hybrid
grown at Quincy, Florida, in 1940. Note uniformity.)

Corn Varieties and Hybrids

The "hybrid method" with corn accomplishes virtually
the same result as vegetative propagation-mass production of
superior individuals which are identical in their heredity. Hy-
brid corn beais much the same relation to open-pollinated corn
that budded progeny of a superior fruit tree bear to seedling
progeny from the same tree. Carrying that comparison further,
it is generally recognized that seedlings from a superior budded
fruit tree are usually inferior to the parent. By the same token,
seed from a superior hybrid corn produces inferior progeny.
Hybrid corn is reproduced anew each year by recrossing the
inbred parents lines. Farmer's crop hybrid corn should never be
planted as seed.
-'The term "hybrid corn" by common consent, and by legis-
lation in some states, has been restricted in recent years to mean
the first generation, only, of a cross involving at least one in-
bred line. Common hybrids are:
1. Topcross or in-bred-variety cross: the cross of an inbred
line with an ordinary variety
2. Single cross: the cross of two inbred lines
3. Three-way cross: the cross of an inbred line with an un-
related single cross, thus involving three inbred lines
4. Double cross: the cross of two unrelated single crosses,
thus involving four different inbred lines.
There are, of course, other possible hybrid combinations,
but the four listed here are the only ones used commercially to
any extent. The single cross is widely used with sweet corn. The
double cross is the most feasible one and the one most used with
field corn. Ears of the four inbred lines, two single crosses, and
the double cross hybrid, Fla. W-l, are placed in Figure 17, to
show how the double cross is made.
vA complete program with hybrid corn involves first the de-
velopment of superior hybrids that are adapted to the climate and
soil of the region where they are to be grown. When a good hy-
brid has been developed, commercial production and planting
of hybrid seed corn may begin.
The preliminary process of developing good hybrids requires
several years. Steps in the process are: (1) Collection of founda-
tion stocks; (2) inbreeding, usually self-pollination by hand,
which must be done separately every year with each line as


Florida Agricultural Experiment Station

Fig. 17.-Illustrating how double cross hybrid seed corn is produced
by crossing four inbred lines; first by pairs to produce two single crosses
and second by crossing the two single crosses. The pedigrees are of the
Florida Agricultural Experiment Station hybrid Fla. W-1.
long as it is kept in existence; and (3) test crossing of the best
appearing lines which may begin after one to three years of in-
breeding, and must be continued at least three years before any
hybrid can be safely considered acceptable for commercial use.
Development of hybrid corn by the Florida Experiment
Station began in 1927 when some 500 self-pollinations were made
on border rows of plots in the regular variety tests. Other new
self-pollinations were then made in the four following years until
10,000 inbred lines had been started. Most of these came from
a few varieties which had made the best records in earlier tests.
Some were derived from a single variety and others from crosses
of prolific varieties with native, one-eared, weevil-resistant va-
rieties. Here again, as with the foundation stock of the Florident

Corn Varieties and Hybrids


Fig. 18.-Two inbred lines of corn (in foreground), one badly lodged,
the other fully erect.
White and Florident Yellow varieties, the purpose was to com-
bine prolificacy and high yield with weevil resistance.
Many inbred lines with obvious defects were discarded im-
mediately (Figure 18.) Other lines did not produce enough seed
to plant again and were lost. Each year some of the poorer ap-
pearing lines were discarded until only 500 were left of the
original 10,000. These lines were stable and uniform but of many
different types. Each line seemed vigorous enough for use in the
commercial production of hybrid seed.
The next step was to test the behavior of inbred lines in

Florida Agricultural Experiment Station

crosses to determine which ones might make the best hybrids. It
may be noted now that 124,750 different single crosses and a
much larger number of double crosses may be made from 500
inbred lines. It was clearly impracticable to test that many hy-
brids. The inbred lines were first crossed with the variety What-
ley Prolific for a preliminary test. Those making the best records
were later combined into single and double crosses for further
testing1. Many of the test crosses were grown on the Experiment
Station farms at Quincy and Gainesville. Records were kept in
each test on yield, weevily ears, ear rot, and lodging of the plants.
It was found that appearance of inbred lines is not a reliable in-
dication of yields produced by their hybrids. Lines which made
good yields in crosses with Whatley usually made good yields
when crossed with each other. However, a few lines were discov-
ered which produced two-eared hybrids and good yields in
crosses with Whatley but mostly one-eared hybrids and relatively
low yields when crossed with each other. Most of the hybrids
made relatively lower yields in comparison with Whatley Pro-
lific and other check varieties at Quincy than at Gainesville.
That result was not unexpected, since the inbred lines were de-
veloped at Gainesville and only those passing preliminary tests
at Gainesville were included in tests at Quincy. Development of
strong stalks, strong root systems, good husk protection, flinti-
ness, and freedom from diseases in hybrids is apparently de-
pendent upon a high average development of those characters
in the component inbred lines.
With the first cycle of breeding work completed, 50 inbred
lines have been retained from 10,000 original self-pollinations
made in open-pollinated varieties and crosses of such varieties.
Every one of the 50 lines has one or more serious faults. A second
cycle of breeding now in progress has so far produced 5,000
new lines derived from various combinations of the better lines
in the older group. Many of these new lines have been discarded,
but a goodly number of them appear definitely superior to any
of the older group. Testing of their hybrids is in the early stages,
but it seems likely that some of them may soon replace certain
lines that are now recommended in the double cross hybrid,
Fla. W-l. It also seems likely that a satisfactory yellow hybrid
combination may be found among the new yellow lines.

'The making of test crosses did not impair purity of the lines, for
each inbred line was continued every year by self-pollination as a sep-
arate process.

Corn Varieties and Hybrids

Fla. W-1 is the only hybrid corn that has been released by
the Florida Agricultural Experiment Station. It is the double
cross of four inbred lines
developed by breeding work
discussed in the preceding
section. The four inbred lines
and the two single crosses
which combine to make Fla.
.... W-1 are described here be-
~- fore presenting a proposed
plan for commercial produc-
.. 6 tion of the hybrid seed.

/1 5



Fig. 19.-Inbred line 11-129. T
ears and plant.

These descriptions must
not be considered exact,
since many characters of the
corn plant vary a great deal
with changes of climate and
soil. Pictures of one plant
and two ears of each line and
single cross are shown in
Figures 19 to 24. A descrip-
tion of Fla. W-l is given with
other commercial hybrids
and varieties of corn in a
previous section of this bul-
letin. The pedigree of Fla.
W-l is (11-129x4-32) x


Origin-Whatley Prolific,
first self-pollination made in

Characteristics-Very pro-

lific, most productive of the four lines, long tight husks, smooth

Florida Agricultural Experiment Station

dent kernel type, weak root system allows many growing plants
to lodge in wet weather, white seed, deep red cob. This line sheds
pollen freely and produces many suckers. Nevertheless, it is best
used as the seed parent of the single cross 11-129x4-32 because

I &


/ 4

Fig. 20.-Inbred line 4-32.
ears and plant.

of its higher yield of seed.
Origin-Smith, first self-
pollination made in 1928.
Smith is a white single-eared,
weevil-resistant variety from
M. N. Smith, River Junction,
a Florida. It was included in
early variety tests at Gaines-
Characteristics T w o -
eared with second ear small-
er than the first, long tight
husk, dent kernel type, me-
dium strong root system,
slender stalk, slightly crook-
ed neck causes tassel branch-
es to lean mostly on one side,
white seed, white cob. This
line does not shed pollen as
freely as 11-129 but its seed
production is so much poorer
that it is best used as the
pollen parent for the single
cross 11-129x4-32.
SINGLE CROSS, 11-129x4-32
Origin-Seed made up
anew each year by using pol-
len from 4-32 on silks of
Characteristics Prolific
with three ears on many
a Tlants, production 15 percent

@ ." ^^ E*'-''

Corn Varieties and Hybrids

lower than Fla. W-l, long
tight husks, smooth dent ker-
nels, resistant to weevils, me-
dium strong root system,
may lodge under some con-
ditions, white seed, red cob.
This single cross is recom-
mended for the seed parent
in making the double cross
because of higher production
of inbred line 11-129. Inbred
seed to plant two-thirds of
the larger single crossing
plot and single cross seed to
plant three fourths of the
double crossing field are
both borne on plants of one
of the four inbred lines. The
most productive line, 11-129,
is recommended for that


Origin-F lorida Flint
crossed with Cuban Flint in
1926, self-pollinated 1927,
outcrossed 1928, first self-
pollination to start B5-11
made in 1929.
Characteristics T w o -
eared, second best producer
of the four lines in Fla. W-l,
first ear often fails, long
tight husks, flint type ker-
nels, medium strong root
system, white seed, white
cob. This line is used as the
seed parent in the single
cross B5-11xB1-18 because
it is more productive than

Fig. 21.-Single cross 11-129
x 4-32. Typical ears and plant.

Florida Agricultural Experiment Station

Origin-Cuban Yellow Flint self-pollinated 1927, outcrossed


Fig. 22.-Inbred line B5-11.
ears and plant.

1928, first self-pollination to
start B1-18 made in 1929.
Characteristics T w o -
eared with second ear small-
er than first, least productive
of the four lines in Fla. W-l,
long tight husks, semi-flint
type kernels, very strong
S root system, seed ordinarily
pass as white but do have
faint yellow tinge, white cob,
ear presses tightly against
stalk frequently causing
crook of the stalk as shown
in Fig. 23. (That peculiar
character often appears also
in Cuban Yellow Flint corn.)
This inbred line is used as
pollen parent in the single
cross B5-llxBl-18 because of
its poor seed production. It
does not shed pollen freely
but pollinates B5-11 satisfac-
2 Origin Seed made up
anew each year by using pol-
len from Bl-18 on silks of
S B5-11.
S Characteristics T w o-
eared, production 12 percent
below Fla. W-l, long tight
0 husks, smooth dent kernels,
resistant to weevils, strong
root system, tall slender
stalk, seed ordinarily pass
as white but do have a very
faint yellow tinge, white
Typicalcob. This single cross is used

Corn Varieties and Hybrids

* WE
Fig. 23.-Inbred line B1-18. Typical
ears and plant.

as the pollen parent of Fla.
W-l because production of
single cross seed on B5-11
with B1-18 pollen is much
lower than production of
single cross seed on 11-129
with 4-32 pollen. This sin-
gle cross is planted in one
pollen row to every three
seed rows of the other sin-
gle cross in the double
crossing field.
The other four possible
single crosses which may be
made from the four inbred
lines, viz. 11-129 x B5-11, 11-
129 x B1-18, 4-32 x B5-11,
and 4-32 x B1-18, are not de-
scribed here. They are not
used in making double cross
seed because of the three
possible double crosses, viz.
(11-129 x 4-32) x (B5-11 x
Bl-18), (11-129 x B5-11) x
(4-32 x B1-18), and (11-129
x B1-18) x (4-32 x B5-11),
the first produces the best
yields. It is also more prac-
ticable to make that com-
bination because of differ-
ences in seed production of
the four inbred lines.
After four satisfactory in-
bred lines have been devel-
oped and their double cross
hybrid proven by adequate
testing, the process of pro-

Florida Agricultural Experiment Station

during double cross seed
requires three years. Seed
of the inbred lines must be
increased the first year, sin-
gle crosses are made the
second year, and double
cross seed is made the third
year. Seed production may
be made continuous by do-
ing each job every year.
A plan for producing
enough seed of the double
cross, Fla. W-l, to plant
500,000 acres of hybrid corn
(70 percent of the total
acreage of corn in Florida)
is shown in Figure 25. All
parts of the plan must be
in operation every year to
provide continuous produc-
tion of double-cross seed.
The four inbred lines are
shown at the top of the dia-
gram in separate plots to-
taling one-third acre. In-
crease of inbred seed may
be done in four separately
isolated plots, but it will be
easier to handle them by
hand pollination and avoid
the trouble of caring for so
many small, separate plots.
Inbred seed and single cross
seed are both borne on in-
bred plants. They are small-
er than ordinary corn, so
the usual allowance of
planting 10 acres with one
bushel will not apply. tOn
the Experiment Station
farm at Gainesville from
200 to 500 seeds have been
obtained for each hand pol-
linated plant of th inbred
lines of Fla. W-l. lt is esti-
mated here that each inbred
plant will produce 150
daughter plants or that one
RacrE of inlibre or single

FL' 24 -Sirilr cIro B5-11 x
Bl-18. Tyic'' lf f.atr' acnd plant


Corn Varieties and Hybrids

cross seed will plant 150 acres. The one-sixth acre of inbred
line 11-129 will plant 25 acres of seed rows in the larger single
crossing block. This 25 acres will plant 3,750 acres of single
cross seed rows in double crossing. The double cross seed is
borne on these single cross seed rows. Here yields and seed size
are like ordinary corn. It is estimated that each acre of seed
rows in double crossing will produce 15 bushels of graded seed
and each bushel will plant 10 acres. The other three inbred
lines besides 11-129 serve mainly as pollinators in the process.
The whole seed production plan includes one-third acre of inbred
lines, 50 acres of single crossing, and 5,000 acres of double cross-
ing each year. It must be understood that in this process there
is no need to select the finer and larger ears for seed. Breeding
work was completed in the preliminary development of inbred
lines with fixed inheritance. All sound, well developed seeds
produced on seed rows in double crossing are suitable for plant-
The plan for producing hybrid seed is presented here on an
extensive scale. This is not to propose or recommend that Fla.
W-1 be planted so extensively as soon as seed can be produced.
The purpose is to show that the responsibility of supplying the
entire demand for single cross seed in the state will not soon
become too large for the Experiment Station to accept. Another
purpose is to show how quickly an adequate supply of seed of a
new hybrid may be made available. Other hybrids may be com-
peting with Fla. W-l very soon in some sections of the state. The
whole seed production plan will then be divided between differ-
ent hybrids. If the State Experiment Station does the two jobs
of increasing inbred seed and producing single cross seed, much
of the intricacy of producing double cross seed will disappear so
far as private seed growers are concerned. Farmers or commer-
cial seed growers may obtain seed of the two single crosses and
combine them to make double cross hybrid seed in isolated de-
tasseling fields, with only one crossing operation.
Fields to be used for producing hybrid seed corn should be
free of volunteer corn plants of any kind. Plants that are off-
type should be cut down before silks and tassels appear. The
work should be done on good land and the best cultural care
should be given to growing the crop. Under such conditions a
ratio of three or even four seed rows to one pollen row will be
satisfactory in double crossing. With less favorable growing
conditions where planting rates are not so thick, one pollen row

Florida Agricultural Experiment Station

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50 Florida Agricultural Experiment Station

fall and winter. Florident Yellow will also be satisfactory for
silage on all mineral soils of the state except in the extreme
southern part.
Wood Hybrid Golden Prolific may be used in small plantings
to provide feed through a period of one to two weeks before later
types of corn are ready to feed.
It is strongly recommended that hybrid corn from any source
be tried first on a small acreage before making a large planting.
Do not plant seed from a crop of hybrid corn regardless of
how excellent the crop may be.

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