According to the invention, there is provided a hybrid maize plant, designated as 33Y18, produced by crossing two Pioneer Hi-Bred International, Inc. proprietary inbred maize lines. This invention relates to the hybrid seed 33Y18, the hybrid plant produced from the seed, and variants, mutants, and trivial modifications of hybrid 33Y18.

FIELD OF THE INVENTION 
This invention is in the field of maize breeding, specifically relating to 
a hybrid maize line designated 33Y18. 
BACKGROUND OF THE INVENTION 
Plant Breeding 
Field crops are bred through techniques that take advantage of the plants 
method of pollination. A plant is self-pollinated if pollen from one 
flower is transferred to the same or another flower of the same plant. A 
plant is cross-pollinated if the pollen comes from a flower on a different 
plant. 
Plants that have been self-pollinated and selected for type for many 
generations become homozygous at almost all gene loci and produce a 
uniform population of true breeding progeny. A cross between two different 
homozygous lines produces a uniform population of hybrid plants that may 
be heterozygous for many gene loci. A cross of two plants each 
heterozygous at a number of gene loci will produce a population of hybrid 
plants that differ genetically and will not be uniform. 
Maize (Zea mays L.), often referred to as corn in the United States, can be 
bred by both self-pollination and cross-pollination techniques. Maize has 
separate male and female flowers on the same plant, located on the tassel 
and the ear, respectively. Natural pollination occurs in maize when wind 
blows pollen from the tassels to the silks that protrude from the tops of 
the ears. 
The development of a hybrid maize variety involves three steps: (1) the 
selection of plants from various germplasm pools for initial breeding 
crosses; (2) the selfing of the selected plants from the breeding crosses 
for several generations to produce a series of inbred lines, which, 
although different from each other, breed true and are highly uniform; and 
(3) crossing the selected inbred lines with unrelated inbred lines to 
produce the hybrid progeny (F.sub.1). During the inbreeding process in 
maize, the vigor of the lines decreases. Vigor is restored when two 
different inbred lines are crossed to produce the hybrid progeny 
(F.sub.1). An important consequence of the homozygosity and homogeneity of 
the inbred lines is that the hybrid created by crossing a defined pair of 
inbreds will always be the same. Once the inbreds that create a superior 
hybrid have been identified, a continual supply of the hybrid seed can be 
produced using these inbred parents and the hybrid corn plants can then be 
generated from this hybrid seed supply. 
Large scale commercial maize hybrid production, as it is practiced today, 
requires the use of some form of male sterility system which controls or 
inactivates male fertility. A reliable method of controlling male 
fertility in plants also offers the opportunity for improved plant 
breeding. This is especially true for development of maize hybrids, which 
relies upon some sort of male sterility system. There are several options 
for controlling male fertility available to breeders, such as: manual or 
mechanical emasculation (or detasseling), cytoplasmic male sterility, 
genetic male sterility, gametocides and the like. 
Hybrid maize seed is typically produced by a male sterility system 
incorporating manual or mechanical detasseling. Alternate strips of two 
inbred varieties of maize are planted in a field, and the pollen-bearing 
tassels are removed from one of the inbreds (female) prior to pollen shed. 
Providing that there is sufficient isolation from sources of foreign maize 
pollen, the ears of the detasseled inbred will be fertilized only from the 
other inbred (male), and the resulting seed is therefore hybrid and will 
form hybrid plants. 
The laborious, and occasionally unreliable, detasseling process can be 
avoided by using cytoplasmic male-sterile (CMS) inbreds. Plants of a CMS 
inbred are male sterile as a result of factors resulting from the 
cytoplasmic, as opposed to the nuclear, genome. Thus, this characteristic 
is inherited exclusively through the female parent in maize plants, since 
only the female provides cytoplasm to the fertilized seed. CMS plants are 
fertilized with pollen from another inbred that is not male-sterile. 
Pollen from the second inbred may or may not contribute genes that make 
the hybrid plants male-fertile. Usually seed from detasseled fertile maize 
and CMS produced seed of the same hybrid are blended to insure that 
adequate pollen loads are available for fertilization when the hybrid 
plants are grown. 
There are several methods of conferring genetic male sterility available, 
such as multiple mutant genes at separate locations within the genome that 
confer male sterility, as disclosed in U.S. Pat. Nos. 4,654,465 and 
4,727,219 to Brar et al. and chromosomal translocations as described by 
Patterson in U.S. Pat. Nos. 3,861,709; and 3,710,511. These and all 
patents referred to are incorporated by reference. In addition to these 
methods, Albertsen et al., of Pioneer Hi-Bred, U.S. patent application 
Ser. No. 07/848,433, have developed a system of nuclear male sterility 
which includes: identifying a gene which is critical to male fertility; 
silencing this native gene which is critical to male fertility; removing 
the native promoter from the essential male fertility gene and replacing 
it with an inducible promoter; inserting this genetically engineered gene 
back into the plant; and thus creating a plant that is male sterile 
because the inducible promoter is not "on" resulting in the male fertility 
gene not being transcribed. Fertility is restored by inducing, or turning 
"on", the promoter, which in turn allows the gene that confers male 
fertility to be transcribed. 
There are many other methods of conferring genetic male sterility in the 
art, each with its own benefits and drawbacks. These methods use a variety 
of approaches such as delivering into the plant a gene encoding a 
cytotoxic substance associated with a male tissue specific promoter or an 
antisense system in which a gene critical to fertility is identified and 
an antisense to that gene is inserted in the plant (see: Fabinjanski, et 
al. EPO 89/3010153.8 publication no. 329,308 and PCT application 
PCT/CA90/00037 published as WO 90/08828). 
Another system useful in controlling male sterility makes use of 
gametocides. Gametocides are not a genetic system, but rather a topical 
application of chemicals. These chemicals affect cells that are critical 
to male fertility. The application of these chemicals affects fertility in 
the plants only for the growing season in which the gametocide is applied 
(see Carlson, Glenn R., U.S. Pat. No. 4,936,904). Application of the 
gametocide, timing of the application and genotype specificity often limit 
the usefulness of the approach. 
The use of male sterile inbreds is but one factor in the production of 
maize hybrids. The development of maize hybrids requires, in general, the 
development of homozygous inbred lines, the crossing of these lines, and 
the evaluation of the crosses. Breeding programs combine the genetic 
backgrounds from two or more inbred lines or various other broad-based 
sources into breeding pools from which new inbred lines are developed by 
selfing and selection of desired phenotypes. The new inbreds are crossed 
with other inbred lines and the hybrids from these crosses are evaluated 
to determine which of those have commercial potential. 
There are many important factors to be considered in the art of plant 
breeding, such as the ability to recognize important morphological and 
physiological characteristics, the ability to design evaluation techniques 
for genotypic and phenotypic traits of interest, and the ability to search 
out and exploit the genes for the desired traits in new or improved 
combinations. 
The objective of commercial maize hybrid line development programs is to 
develop new inbred lines to produce hybrids that combine to produce high 
grain yields and superior agronomic performance. The primary trait 
breeders seek is yield. However, many other major agronomic traits are of 
importance in hybrid combination and have an impact on yield or otherwise 
provide superior performance in hybrid combinations. Such traits include 
percent grain moisture at harvest, relative maturity, resistance to stalk 
breakage, resistance to root lodging, grain quality, and disease and 
insect resistance. In addition, the lines per se must have acceptable 
performance for parental traits such as seed yields, kernel sizes, pollen 
production, all of which affect ability to provide parental lines in 
sufficient quantity and quality for hybridization. These traits have been 
shown to be under genetic control and many if not all of the traits are 
affected by multiple genes. 
Pedigree Breeding 
The pedigree method of breeding is the mostly widely used methodology for 
new hybrid line development. 
In general terms this procedure consists of crossing two inbred lines to 
produce the non-segregating F.sub.1 generation, and self pollination of 
the F.sub.1 generation to produce the F.sub.2 generation that segregates 
for all factors for which the inbred parents differ. An example of this 
process is set forth below. Variations of this generalized pedigree method 
are used, but all these variations produce a segregating generation which 
contains a range of variation for the traits of interest.

EXAMPLE 1 
Hypothetical Example of Pedigree Breeding Program 
Consider a cross between two inbred lines that differ for alleles at six 
loci. The parental genotypes are: 
______________________________________ 
Parent 1 A b C d e F/A b C d e F 
Parent 2 a B c D E f/a B c D E f 
______________________________________ 
the F.sub.1 from a cross between these two parents is: 
______________________________________ 
F.sub.1 A b C d e F/a B c D E f 
______________________________________ 
Selfing F.sub.1 will produce an F.sub.2 generation including the following 
genotypes: 
______________________________________ 
A B c D E f/a b C d e F 
A B c D e f/a b C d E F 
A B c D e f/ a b C d e F 
______________________________________ 
The number of genotypes in the F.sub.2 is 3.sup.6 for six segregating loci 
(729) and will produce (2.sup.6)-2 possible new inbreds, (62 for six 
segregating loci). 
Each inbred parent which is used in breeding crosses represents a unique 
combination of genes, and the combined effects of the genes define the 
performance of the inbred and its performance in hybrid combination. There 
is published evidence (Smith, O. S., J. S. C. Smith, S. L. Bowen, R. A. 
Tenborg and S. J. Wall, TAG 80:833-840 (1990)) that each of the lines are 
different and can be uniquely identified on the basis of 
genetically-controlled molecular markers. 
It has been shown (Hallauer, Arnel R. and Miranda, J. B. Fo. Quantitative 
Genetics in Maize Breeding, Iowa State University Press, Ames, Iowa, 1981) 
that most traits of economic value in maize are under the genetic control 
of multiple genetic loci, and that there are a large number of unique 
combinations of these genes present in elite maize germplasm. If not, 
genetic progress using elite inbred lines would no longer be possible. 
Studies by Duvick and Russell (Duvick, D. N., Maydica 37:69-79, (1992); 
Russell, W. A., Maydica XXIX:375-390 (1983)) have shown that over the last 
50 years the rate of genetic progress in commercial hybrids has been 
between one and two percent per year. 
The number of genes affecting the trait of primary economic importance in 
maize, grain yield, has been estimated to be in the range of 10-1000. 
Inbred lines which are used as parents for breeding crosses differ in the 
number and combination of these genes. These factors make the plant 
breeder's task more difficult. Compounding this is evidence that no one 
line contains the favorable allele at all loci, and that different alleles 
have different economic values depending on the genetic background and 
field environment in which the hybrid is grown. Fifty years of breeding 
experience suggests that there are many genes affecting grain yield and 
each of these has a relatively small effect on this trait. The effects are 
small compared to breeders' ability to measure grain yield differences in 
evaluation trials. Therefore, the parents of the breeding cross must 
differ at several of these loci so that the genetic differences in the 
progeny will be large enough that breeders can develop a line that 
increases the economic worth of its hybrids over that of hybrids made with 
either parent. 
If the number of loci segregating in a cross between two inbred lines is n, 
the number of unique genotypes in the F.sub.2 generation is 3.sup.n and 
the number of unique inbred lines from this cross is {(2.sup.n)-2}. Only a 
very limited number of these combinations are useful. Only about 1 in 
10,000 of the progeny from F.sub.2 's are commercially useful. 
By way of example, if it is assumed that the number of segregating loci in 
F.sub.2 is somewhere between 20 and 50, and that each parent is fixed for 
half the favorable alleles, it is then possible to calculate the 
approximate probabilities of finding an inbred that has the favorable 
allele at {(n/2)+m} loci, where n/2 is the number of favorable alleles in 
each of the parents and m is the number of additional favorable alleles in 
the new inbred. See Example 2 below. The number m is assumed to be greater 
than three because each allele has so small an effect that evaluation 
techniques are not sensitive enough to detect differences due to three or 
less favorable alleles. The probabilities in Example 2 are on the order of 
10.sup.-5 or smaller and they are the probabilities that at least one 
genotype with (n/2)=m favorable alleles will exist. 
To put this in perspective, the number of plants grown on 60 million acres 
(approximate United States corn acreage) at 25,000 plants/acre is 
1.5.times.10.sup.12. 
EXAMPLE 2 
Probability of Finding an Inbred with m of n Favorable Alleles 
Assume each parent has n/2 of the favorable alleles and only 1/2 of the 
combinations of loci are economically useful. 
______________________________________ 
No. of No. of favorable 
No. additional 
Probability 
segregating 
alleles in Parents 
favorable alleles in 
that genotype 
loci (n) 
(n/2) new inbred occurs* 
______________________________________ 
20 10 14 3 .times. 10.sup.-5 
24 12 16 2 .times. 10.sup.-5 
28 14 18 1 .times. 10.sup.-5 
32 16 20 8 .times. 10.sup.-6 
36 18 22 5 .times. 10.sup.-6 
40 20 24 3 .times. 10.sup.-6 
44 22 26 2 .times. 10.sup.-6 
48 24 28 1 .times. 10.sup.-6 
______________________________________ 
*Probability that a useful combination exists, does not include the 
probability of identifying this combination if it does exist. 
The possibility of having a usably high probability of being able to 
identify this genotype based on replicated field testing would be most 
likely smaller than this, and is a function of how large a population of 
genotypes is tested and how testing resources are allocated in the testing 
program. 
SUMMARY OF THE INVENTION 
According to the invention, there is provided a hybrid maize plant, 
designated as 33Y18, produced by crossing two Pioneer Hi-Bred 
International, Inc. proprietary inbred maize lines. This invention thus 
relates to the hybrid seed 33Y18, the hybrid plant produced from the seed, 
and variants, mutants and trivial modifications of hybrid 33Y18. This 
hybrid maize plant is characterized by consistent high yields over a wide 
area of the corn belt. Hybrid 33Y18 shows improved Gray Leaf Spot 
resistance, good stalk strength, high test weight and excellent early 
growth. Hybrid 33Y18 exhibits tall plant stature and late season plant 
intactness. 
DEFINITIONS 
In the description and examples that follow, a number of terms are used 
herein. In order to provide a clear and consistent understanding of the 
specification and claims, including the scope to be given such terms, the 
following definitions are provided. NOTE: ABS is in absolute terms and % 
MN is percent of the mean for the experiments in which the inbred or 
hybrid was grown. These designators will follow the descriptors to denote 
how the values are to be interpreted. Below are the descriptors used in 
the data tables included herein. 
ANT ROT=ANTHRACNOSE STALK ROT (Colletotrichum graminicola). A 1 to 9 visual 
rating indicating the resistance to Anthracnose Stalk Rot. A higher score 
indicates a higher resistance. 
BAR PLT=BARREN PLANTS. The percent of plants per plot that were not barren 
(lack ears). 
BRT STK=BRITTLE STALKS. This is a measure of the stalk breakage near the 
time of pollination, and is an indication of whether a hybrid or inbred 
would snap or break near the time of flowering under severe winds. Data 
are presented as percentage of plants that did not snap in paired 
comparisons and on a 1 to 9 scale (9=highest resistance) in 
Characteristics Charts. 
BU ACR=YIELD (BUSHELS/ACRE). Yield of the grain at harvest in bushels per 
acre adjusted to 15.5% moisture. 
CLN=CORN LETHAL NECROSIS (synergistic interaction of maize chlorotic mottle 
virus (MCMV) in combination with either maize dwarf mosaic virus (MDMV-A 
or MDMV-B) or wheat streak mosaic virus (WSMV)). A 1 to 9 visual rating 
indicating the resistance to Corn Lethal Necrosis. A higher score 
indicates a higher resistance. 
COM RST=COMMON RUST (Puccinia sorghi). A 1 to 9 visual rating indicating 
the resistance to Common Rust. A higher score indicates a higher 
resistance. 
CRM=COMATIVE RELATIVE MATURITY (see PRM). 
D/D DRYDOWN. This represents the relative rate at which a hybrid will reach 
acceptable harvest moisture compared to other hybrids on a 1-9 rating 
scale. A high score indicates a hybrid that dries relatively fast while a 
low score indicates a hybrid that dries slowly. 
D/E=DROPPED EARS. Represented in a 1 to 9 scale in the Characteristics 
Chart, where 9 is the rating representing the least, or no, dropped ears. 
DIP ERS=DIPLODIA EAR MOLD SCORES (Diplodia maydis and Diplodia macrospora). 
A 1 to 9 visual rating indicating the resistance to Diplodia Ear Mold. A 
higher score indicates a higher resistance. 
DRP EAR=DROPPED EARS. A measure of the number of dropped ears per plot and 
represents the percentage of plants that did not drop ears prior to 
harvest. 
D/T=DROUGHT TOLERANCE. This represents a 1-9 rating for drought tolerance, 
and is based on data obtained under stress conditions. A high score 
indicates good drought tolerance and a low score indicates poor drought 
tolerance. 
EAR HT=EAR HEIGHT. The ear height is a measure from the ground to the 
highest placed developed ear node attachment and is measured in inches. 
This is represented in a 1 to 9 scale in the Characteristics Chart, where 
9 is highest. 
EAR MLD=General Ear Mold. Visual rating (1-9 score) where a "1" is very 
susceptible and a "9" is very resistant. This is based on overall rating 
for ear mold of mature ears without determining the specific mold 
organism, and may not be predictive for a specific ear mold. 
EAR SZ=EAR SIZE. A 1 to 9 visual rating of ear size. The higher the rating 
the larger the ear size. 
ECB 1LF=EUROPEAN CORN BORER FIRST GENERATION LEAF FEEDING (Ostrinia 
nubilalis). A 1 to 9 visual rating indicating the resistance to 
preflowering leaf feeding by first generation European Corn Borer. A 
higher score indicates a higher resistance. 
ECB 2IT=EUROPEAN CORN BORER SECOND GENERATION INCHES OF TUNNELING (Ostrinia 
nubilalis). Average inches of tunneling per plant in the stalk. 
ECB 2SC=EUROPEAN CORN BORER SECOND GENERATION (Ostinia nubilalis). A 1 to 9 
visual rating indicating post flowering degree of stalk breakage and other 
evidence of feeding by European Corn Borer, Second Generation. A higher 
score indicates a higher resistance. 
ECB DPE=EUROPEAN CORN BORER DROPPED EARS (Ostrinia nubilalis). Dropped ears 
due to European Corn Borer. Percentage of plants that did not drop ears 
under second generation corn borer infestation. 
E/G=EARLY GROWTH. This represents a 1 to 9 rating for early growth, scored 
when two leaf collars are visible. A higher rating indicates a taller 
plant than does a lower rating. 
EST CNT=EARLY STAND COUNT. This is a measure of the stand establishment in 
the spring and represents the number of plants that emerge on per plot 
basis for the inbred or hybrid. 
EYE SPT=Eye Spot (Kabatiella zeae or Aureobasidium zeae). A 1 to 9 visual 
rating indicating the resistance to Eye Spot. A higher score indicates a 
higher resistance. 
FUS ERS=FUSARIUM EAR ROT SCORE (Fusarium moniliforme or Fusarium 
subglutinans). A 1 to 9 visual rating indicating the resistance to 
Fusarium ear rot. A higher score indicates a higher resistance. 
G/A=GRAIN APPEARANCE. Appearance of grain in the grain tank (scored down 
for mold, cracks, red streak, etc.). 
GDU=Growing Degree Units. Using the Barger Heat Unit Theory, that assumes 
that maize growth occurs in the temperature range 50.degree. F. 
-86.degree. F. and that temperatures outside this range slow down growth; 
the maximum daily heat unit accumulation is 36 and the minimum daily heat 
unit accumulation is 0. The seasonal accumulation of GDU is a major factor 
in determining maturity zones. 
GDU PHY=GDU TO PHYSIOLOGICAL MATURITY. The number of growing degree units 
required for an inbred or hybrid line to have approximately 50 percent of 
plants at physiological maturity from time of planting. Growing degree 
units are calculated by the Barger method. 
GDU SHD=GDU TO SHED. The number of growing degree units (GDUs) or heat 
units required for an inbred line or hybrid to have approximately 50 
percent of the plants shedding pollen and is measured from the time of 
planting. Growing degree units are calculated by the Barger Method, where 
the heat units for a 24-hour period are: 
##EQU1## 
The highest maximum temperature used is 86.degree. F. and the lowest 
minimum temperature used is 50.degree. F. For each inbred or hybrid it 
takes a certain number of GDUs to reach various stages of plant 
development. 
GDU SLK=GDU TO SILK. The number of growing degree units required for an 
inbred line or hybrid to have approximately 50 percent of the plants with 
silk emergence from time of planting. Growing degree units are calculated 
by the Barger Method as given in GDU SHD definition. 
GIB ERS=GIBBERELLA EAR ROT (PINK MOLD) (Gibberella zeae). A 1 to 9 visual 
rating indicating the resistance to Gibberella Ear Rot. A higher score 
indicates a higher resistance. 
GLF SPT=Gray Leaf Spot (Cercospora zeae-maydis). A 1 to 9 visual rating 
indicating the resistance to Gray Leaf Spot. A higher score indicates a 
higher resistance. 
GOS WLT=Goss' Wilt (Corynebacterium nebraskense). 1 to 9 visual rating 
indicating the resistance to Goss' Wilt. A higher score indicates a higher 
resistance. 
GRN APP=GRAIN APPEARANCE. This is a I to 9 rating for the general 
appearance of the shelled grain as it is harvested based on such factors 
as the color of harvested grain, any mold on the grain, and any cracked 
grain. High scores indicate good grain quality. 
H/POP=YIELD AT HIGH DENSITY. Yield ability at relatively high plant 
densities on 1-9 relative rating system with a higher number indicating 
the hybrid responds well to high plant densities for yield relative to 
other hybrids. A 1, 5, and 9 would represent very poor, average, and very 
good yield response, respectively, to increased plant density. 
HC BLT=HELMINTHOSPORIUM CARBONUM LEAF BLIGHT (Helminthosporium carbonum). A 
1 to 9 visual rating indicating the resistance to Helminthosporium 
infection. A higher score indicates a higher resistance. 
HD SMT=HEAD SMUT (Sphacelotheca reiliana). This score indicates the 
percentage of plants not infected. 
INC D/A=GROSS INCOME (DOLLARS PER ACRE). Relative income per acre assuming 
drying costs of two cents per point above 15.5 percent harvest moisture 
and current market price per bushel. 
INCOME/ACRE. Income advantage of hybrid to be patented over other hybrid on 
per acre basis. 
INC ADV=GROSS INCOME ADVANTAGE. GROSS INCOME advantage of variety #1 over 
variety #2. 
L/POP=YIELD AT LOW DENSITY. Yield ability at relatively low plant densities 
on a 1-9 relative system with a higher number indicating the hybrid 
responds well to low plant densities for yield relative to other hybrids. 
A 1, 5, and 9 would represent very poor, average, and very good yield 
response, respectively, to low plant density. 
MDM CPX=MAIZE DWARF MOSAIC COMPLEX (MDMV=Maize Dwarf Mosaic Virus and 
MCDV=Maize Chlorotic Dwarf Virus). A 1 to 9 visual rating indicating the 
resistance to Maize Dwarf Mosaic Complex. A higher score indicates a 
higher resistance. 
MST=HARVEST MOISTURE. The moisture is the actual percentage moisture of the 
grain at harvest. 
MST ADV=MOISTURE ADVANTAGE. The moisture advantage of variety #1 over 
variety #2 as calculated by: MOISTURE of variety #2-MOISTURE of variety 
#1=MOISTURE ADVANTAGE of variety #1. 
NLF BLT=Northern Leaf Blight (Helminthosporium turcicum or Exserohilum 
turcicum). A 1 to 9 visual rating indicating the resistance to Northern 
Leaf Blight. A higher score indicates a higher resistance. 
PHY CRM=CRM at physiological maturity. 
PLT HT=PLANT HEIGHT. This is a measure of the height of the plant from the 
ground to the tip of the tassel in inches. This is represented as a 1 to 9 
scale, 9 highest, in the Characteristics Chart. 
POL SC=POLLEN SCORE. A 1 to 9 visual rating indicating the amount of pollen 
shed. The higher the score the more pollen shed. 
POL WT=POLLEN WEIGHT. This is calculated by dry weight of tassels collected 
as shedding commences minus dry weight from similar tassels harvested 
after shedding is complete. 
It should be understood that the inbred can, through routine manipulation 
of cytoplasmic or other factors, be produced in a male-sterile form. Such 
embodiments are also contemplated within the scope of the present claims. 
POP K/A=PLANT POPULATIONS. Measured as 1000s per acre. 
POP ADV=PLANT POPULATION ADVANTAGE. The plant population advantage of 
variety #1 over variety #2 as calculated by PLANT POPULATION of variety 
#2-PLANT POPULATION of variety #1=PLANT POPULATION ADVANTAGE of variety 
#1. 
PRM=PREDICTED Relative Maturity. This trait, predicted relative maturity, 
is based on the harvest moisture of the grain. The relative maturity 
rating is based on a known set of checks and utilizes standard linear 
regression analyses and is referred to as the Comparative Relative 
Maturity Rating System that is similar to the Minnesota Relative Maturity 
Rating System. 
PRM SHD=A relative measure of the growing degree units (GDU) required to 
reach 50% pollen shed. Relative values are predicted values from the 
linear regression of observed GDU's on relative maturity of commercial 
checks. 
PRO=PROTEIN RATING. Rating on a 1 to 9 scale comparing relative amount of 
protein in the grain compared to hybrids of similar maturity. A "1" score 
difference represents a 0.4 point change in grain protein percent (e.g., 
8.0% to 8.4%). 
P/Y=PROTEIN/YIELD RATING. Indicates, on a 1 to 9 scale, the economic value 
of a hybrid for swine and poultry feeders. This takes into account the 
income due to yield, moisture and protein content. 
ROOTS (%)=Percent of stalks NOT root lodged at harvest. 
R/L=ROOT LODGING. A 1 to 9 rating indicating the level of root lodging 
resistance. The higher score represents higher levels of resistance. 
RT LDG=ROOT LODGING. Root lodging is the percentage of plants that do not 
root lodge; plants that lean from the vertical axis as an approximately 
30.degree. angle or greater would be counted as root lodged. 
RTL ADV=ROOT LODGING ADVANTAGE. The root lodging advantage of variety #1 
over variety #2. 
S/L=STALK LODGING. A 1 to 9 rating indicating the level of stalk lodging 
resistance. The higher scores represent higher levels of resistance. 
SCT GRN=SCATTER GRAIN. A 1 to 9 visual rating indicating the amount of 
scatter grain (lack of pollination or kernel abortion) on the ear. The 
higher the score the less scatter grain. 
SDG VGR=SEEDLING VIGOR. This is the visual rating (1 to 9) of the amount of 
vegetative growth after emergence at the seedling stage (approximately 
five leaves). A higher score indicates better vigor. 
SEL IND=SELECTION INDEX. The selection index gives a single measure of the 
hybrid's worth based on information for up to five traits. A maize breeder 
may utilize his or her own set of traits for the selection index. One of 
the traits that is almost always included is yield. The selection index 
data presented in the tables represent the mean value averaged across 
testing stations. 
SLF BLT=SOUTHERN LEAF BLIGHT (Helminthosporium maydis or Bipolaris maydis). 
A 1 to 9 visual rating indicating the resistance to Southern Leaf Blight. 
A higher score indicates a higher resistance. 
SLK CRM=CRM at Silking. 
SOU RST=SOUTHERN RUST (Puccinia polysora). A 1 to 9 visual rating 
indicating the resistance to Southern Rust. A higher score indicates a 
higher resistance. 
STA GRN=STAY GREEN. Stay green is the measure of plant health near the time 
of black layer formation (physiological maturity). A high score indicates 
better late-season plant health. 
STAND (%)=Percent of stalks standing at harvest. 
STD ADV=STALK STANDING ADVANTAGE. The advantage of variety #1 over variety 
#2 for the trait STK CNT. 
STK CNT=NUMBER OF PLANTS. This is the final stand or number of plants per 
plot. 
STK LDG=STALK LODGING. This is the percentage of plants that did not stalk 
lodge (stalk breakage) as measured by either natural lodging or pushing 
the stalks and determining the percentage of plants that break below the 
ear. 
STW WLT=Stewart's Wilt (Erwinia stewartii). A 1 to 9 visual rating 
indicating the resistance to Stewart's Wilt. A higher score indicates a 
higher resistance. 
TAS BLS=TASSEL BLAST. A 1 to 9 visual rating was used to measure the degree 
of blasting (necrosis due to heat stress) of the tassel at the time of 
flowering. A 1 would indicate a very high level of blasting at time of 
flowering, while a 9 would have no tassel blasting. 
TAS SZ=TASSEL SIZE. A 1 to 9 visual rating was used to indicate the 
relative size of the tassel. The higher the rating the larger the tassel. 
TAS WT=TASSEL WEIGHT. This is the average weight of a tassel (grams) just 
prior to pollen shed. 
TEX EAR=EAR TEXTURE. A 1 to 9 visual rating was used to indicate the 
relative hardness (smoothness of crown) of mature grain. A 1 would be very 
soft (extreme dent) while a 9 would be very hard (flinty or very smooth 
crown). 
TIL LER=TILLERS. A count of the number of tillers per plot that could 
possibly shed pollen was taken. Data are given as a percentage of tillers: 
number of tillers per plot divided by number of plants per plot. 
TST WT (CHARACTERISTICS CHART)=Test weight on a 1 to 9 rating scale with a 
9 being the highest rating. 
TST WT=TEST WEIGHT (UNADJUSTED). The measure of the weight of the grain in 
pounds for a given volume (bushel). 
TST WTA=TEST WEIGHT ADJUSTED. The measure of the weight of the grain in 
pounds for a given volume (bushel) adjusted for 15.5 percent moisture. 
TSW ADV=TEST WEIGHT ADVANTAGE. The test weight advantage of variety #1 over 
variety #2. 
WIN M %=PERCENT MOISTURE WINS. 
WIN Y %=PERCENT YIELD WINS. 
YLD=YIELD. It is the same as BU ACR ABS. 
YLD ADV=YIELD ADVANTAGE. The yield advantage of variety #1 over variety #2 
as calculated by: YIELD of variety #1-YIELD variety #2=yield advantage of 
variety #1. 
YLD SC=YIELD SCORE. A 1 to 9 visual rating was used to give a relative 
rating for yield based on plot ear piles. The higher the rating the 
greater visual yield appearance. 
DETAILED DESCRIPTION OF THE INVENTION 
Pioneer Brand Hybrid 33Y18 shows excellent yield and high test weight and 
is consistently high yielding over much of the corn belt. Hybrid 33Y18 
presents good Gray Leaf Spot resistance and improved stalk strength with a 
tall plant stature. Hybrid 33Y18 demonstrates excellent early growth and 
late season plant intactness. 
Pioneer Brand Hybrid 33Y18 is a single cross, yellow endosperm, dent maize 
hybrid with outstanding yield in its maturity. Hybrid 33Y18 has a relative 
maturity of approximately 112 based on the Comparative Relative Maturity 
Rating System for harvest moisture of grain. Hybrid 33Y18 is best adapted 
for the Central Corn Belt, Northeast and Southeast regions of the United 
States. 
This hybrid has the following characteristics based on the data collected 
primarily at Johnston, Iowa. 
TABLE 1 
__________________________________________________________________________ 
VARIETY DESCRIPTION INFORMATION 
VARIETY = 33Y18 
__________________________________________________________________________ 
1. 
TYPE: (describe intermediate types in Comments section): 
2 1 = Sweet 2 = Dent 3 = Flint 4 = Flour 5 = Pop 6 = Ornamental 
2. 
MATURITY: 
HEAT 
DAYS UNITS 
075 1,347.5 
From emergence to 50% of plants in silk 
075 1,356.0 
From emergence to 50% of plants in pollen 
003 0,060.0 
From 10% to 90% pollen shed 
068 1,129.0 
From 50% silk to harvest at 25% moisture 
Standard 
Sample 
3. 
PLANT: Deviation 
Size 
0,296.5 cm Plant Height (to tassel tip) 
4.95 2 
0,131.5 cm Ear Height (to base of top ear node) 
16.26 
2 
0,019.7 cm Length of Top Ear Internode 
2.12 10 
1 Average Number of Tillers 0.00 2 
1.0 Average Number of Ears per Stalk 
0.00 2 
1.0 Anthocyanin of Brace Roots: 1 = Absent 2 = Faint 3 = Moderate 
4 = Dark 
Standard 
Sample 
4. 
LEAF: Deviation 
Size 
010.2 cm Width of Ear Node Leaf 0.00 10 
089.8 cm Length of Ear Node Leaf 2.83 10 
06.6 Number of leaves above top ear 
0.28 10 
042.0 Degrees Leaf Angle (measure from 2nd leaf above 
0.00 2 
ear at anthesis to stalk above leaf) 
03 Leaf Color 
Dark Green 
(Munsell code) 
5GY44 
2.0 Leaf Sheath Pubescence (Rate on scale from 1 = none to 9 = 
like peach fuzz) 
5.5 Marginal Waves (Rate on scale from 1 = none to 9 = many) 
8.0 Longitudinal Creases (Rate on scale from 1 = none to 9 = 
many) 
Standard 
Sample 
5. 
TASSEL: Deviation 
Size 
06.0 Number of Primary Lateral Branches 
3.11 10 
033.5 Branch Angle from Central Spike 
16.26 
2 
70.3 cm Tassel Length (from top leaf collar to tassel 
1.56 2 
7.5 Pollen Shed (rate on scale from 0 = male sterile to 9 = heavy 
shed) 
11 Anther Color 
Pink (Munsell code) 
01 Glume Color 
Light Green 
(Munsell code) 
5GY66 
1.0 Bar Glumes (Glume Bands): 1 = Absent 2 = Present 
28 Peduncle Length (cm. from top leaf to basal branches) 
6a. 
EAR (Unhusked Data): 
1 Silk Color (3 days after emergence) 
Light Green 
(Munsell code) 
2.5GY86 
2 Fresh Husk Color (25 days after 50% silking) 
Medium Green 
(Munsell code) 
5GY66 
21 Dry Husk Color (65 days after 50% silking) 
Buff (Munsell code) 
2.5Y84 
1 Position of Ear at Dry Husk Stage: 1 = Upright 2 = Horizontal 3 = 
Pendant Upright 
4 Husk Tightness (Rate of Scale from 1 = very loose to 9 = very 
tight) 
2 Husk Extension (at harvest): 1 = Short (ears exposed) 2 = Medium 
(&lt;8 cm) Medium 
3 = Long (8-10 cm beyond ear tip) 4 = Very Long (&gt;10 cm) 
Standard 
Sample 
6b. 
EAR (Husked Ear Data): Deviation 
Size 
19 cm Ear Length 0.71 10 
48 mm Ear Diameter at mid-point 0.71 10 
205 gm Ear Weight 17.68 
10 
18 Number of Kernel Rows 0.71 10 
2 Kernel Rows: 1 = Indistinct 2 = Distinct 
Distinct 
1 Row Alignment: 1 = Straight 2 = Slightly Curved 3 
Straight 
9 cm Shank Length 0.71 10 
2 Ear Taper: 1 = Slight 2 = Average 3 = Extreme 
Average 
Standard 
Sample 
7. 
KERNEL (Dried): Deviation 
Size 
14 mm Kernel Length 0.71 10 
8 mm Kernel Width 0.00 10 
5 mm Kernel Thickness 0.71 10 
41 % Round Kernels (Shape Grade) 41.01 
2 
1 Aleurone Color Pattern: 1 = Homozygous 2 = Segregating 
Homozygous 
7 Aluerone Color Yellow (Munsell code) 
10YR712 
7 Hard Endosperm Color 
Yellow (Munsell code) 
10YR712 
3 Endosperm Type: Normal Starch 
1 = Sweet (Su1) 2 = Extra Sweet (sh2) 3 = Normal Starch 
4 = High Amylose Starch 5 = Waxy Starch 6 = High Protein 
7 = High Lysine 8 = Super Sweet (se) 9 = High Oil 
10 = Other 
33 gm Weight per 100 Kernels (unsized sample) 
0.71 2 
Standard 
Sample 
8. 
COB: Deviation 
Size 
24 mm Cob Diameter at mid-point 0.00 10 
14 Cob Color Red (Munsell code) 
10R36 
Cob Strength 1 = Weak 2 = Strong 
9. 
DISEASE RESISTANCE (Rate from 1 (most susceptible) to 9 (most 
resistant); leave blank 
if not tested; leave Race or Strain Options blank if polygenic): 
A. Leaf Blights, Wilts, and Local Infection Diseases 
Anthracnose Leaf Blight (Colletotrichum graminicola) 
Common Rust (Puccinia sorghi) 
Common Smut (Ustilago maydis) 
0 Eyespot (Kabatiella zeae) 
Goss's Wilt (Clavibacter michiganense spp. nebraskense) 
6 Gray Leaf Spot (Cercospora zeae-maydis) 
Helminthosporium Leaf Spot (Bipolaris zeicola) Race 
5 Northern Leaf Blight (Exserohilum turcicum) Race 
4 Southern Leaf Blight (Bipolaris maydis) Race 
0 Southern Rust (Puccinia polysora) 
Stewart's Wilt (Erwinia stewartii) 
Other (Specify) 
B. Systemic Diseases 
8 Corn Lethal Necrosis (MCMV and MDMV) 
Head Smut (Sphacelotheca reiliana) 
Maize Chlorotic Dwarf Virus (MDV) 
Maize Chlorotic Mottle Virus (MCMV) 
4 Maize Dwarf Mosaic Virus (MDMV) 
Sorghum Downy Mildew of Corn (Peronosclerospora sorghi) 
Other (Specify) 
C. Stalk Rots 
4 Anthracnose Stalk Rot (Colletotrichum graminicola) 
Diplodia Stalk Rot (Stenocarpella maydis) 
Fusarium Stalk Rot (Fusarium moniliforme) 
Gibberella Stalk Rot (Gibberella zeae) 
Other (Specify) 
D. Ear and Kernel Rots 
Aspergillus Ear and Kernel Rot (Aspergillus flavus) 
0 Diplodia Ear Rot (Stenocarpella maydis) 
6 Fusarium Ear and Kernel Rot (Fusarium moniliforme) 
3 Gibberella Ear Rot (Gibberella zeae) 
Other (Specify) 
Banks grass Mite (Oligonychus pratensis) 
Corn Worm (Helicoverpa zea) 
Leaf Feeding 
Silk Feeding 
mg larval wt. 
Ear Damage 
Corn Leaf Aphid (Rhopalosiphum maidis) 
Corn Sap Beetle (Carpophilus dimidiatus 
European Corn Borer (Ostrinia nubilalis) 
5 1st Generation (Typically Whorl Leaf Feeding) 
7 2nd Generation (Typically Leaf Sheath-Collar Feeding) 
Stalk Tunneling 
0 cm tunneled/plant 
Fall Armyworm (Spodoptera fruqiperda) 
Leaf Feeding 
Silk Feeding 
mg larval wt. 
Maize Weevil (Sitophilus zeamaize 
Northern Rootworm (Diabrotica barberi) 
Southern Rootworm (Diabrotica undecimpunctata) 
Southwestern Corn Borer (Diatreaea grandiosella) 
Leaf Feeding 
Stalk Tunneling 
cm tunneled/plant 
Two-spotted Spider Mite (Tetranychus urticae) 
Western Rootworm (Diabrotica virgifrea virgifera) 
Other (Specify) 
AGRONOMIC TRAITS: 
6 Staygreen (at 65 days after anthesis) (Rate on a scale from 1 = 
worst to excellent) 
4.0 % Dropped Ears (at 65 days after anthesis) 
% Pre-anthesis Brittle Snapping 
% Pre-anthesis Root Lodging 
15.5 Post-anthesis Root Lodging (at 65 days after anthesis) 
11,250 Kg/ha Yield (at 12-13% grain moisture) 
__________________________________________________________________________ 
Research Comparisons for Pioneer Hybrid 33Y18 
Comparisons of characteristics of Pioneer Brand Hybrid 33Y18 were made 
against Pioneer Brand Hybrids 3335, 3394, and 32K61, which are similar in 
adaptation to 33Y18. 
Table 2A compares Pioneer Hybrid 33Y18 and Pioneer Hybrid 3335. The results 
show that both hybrids exhibit above average yields and Hybrid 33Y18 has 
significantly lower harvest moisture and significantly higher test weight 
than Hybrid 3335. Hybrid 33Y18 demonstrates significantly better seedling 
vigor than Hybrid 3335. Hybrid 33Y18 shows a significantly taller plant 
and a significantly higher ear placement than Hybrid 3335. Hybrid 33Y18 
exhibits a significantly better stay green score and shows significantly 
better resistance to stalk lodging and brittle stalk than Hybrid 3335. 
Both hybrids exhibit above average early stand counts. Hybrid 33Y18 
exhibits significantly better resistance to Gray Leaf Spot and shows a 
superior and significantly higher resistance to feeding by second 
generation European Corn Borer than Hybrid 3335. 
Table 2B compares Pioneer Hybrid 33Y18 and Pioneer Hybrid 3394. The results 
show that Hybrid 33Y18 demonstrates an above average and significantly 
higher yield and a significantly higher test weight than Hybrid 3394. Both 
hybrids demonstrate an above average seedling vigor and early stand count. 
Hybrid 33Y18 shows a significantly taller plant and a significantly higher 
ear placement than Hybrid 3394. Hybrid 33Y18 exhibits a significantly 
better stay green score and shows significantly better resistance to stalk 
lodging and brittle stalk than Hybrid 3394. Hybrid 33Y18 exhibits 
significantly better resistance to Gray Leaf Spot and shows a superior and 
significantly higher resistance to feeding by second generation European 
Corn Borer than Hybrid 3394. 
Table 2C compares Pioneer Hybrid 33Y18 and Pioneer Hybrid 32K61. The 
results show that Hybrid 33Y18 exhibits above average and significantly 
higher yields and significantly lower harvest moisture than Hybrid 32K61. 
Both hybrids exhibit high test weights. Hybrid 33Y18 demonstrates both 
significantly better seedling vigor and early sand count than Hybrid 
32K61. Hybrid 33Y18 shows a significantly taller plant and a significantly 
higher ear placement than Hybrid 32K61. Both hybrids have above average 
stay green scores, and above average resistance to stalk lodging and 
brittle stalk. Hybrid 33Y18 exhibits better resistance to Gray Leaf Spot 
and shows a very good and better resistance to feeding by second 
generation European Corn Borer than Hybrid 32K61. 
TABLE 2A 
__________________________________________________________________________ 
HYBRID COMISON REPORT 
VARIETY #1 = 33Y18 
VARIETY #2 = 3335 
__________________________________________________________________________ 
PRM BU BU TST SDG EST GDU GDU 
PRM SHD ACR ACR MST WT VGR CNT SHD SLK 
ABS ABS ABS % MN 
% MN 
ABS % MN % MN 
% MN % MN 
__________________________________________________________________________ 
TOTAL SUM 
1 112 115 175.3 
105 100 57.3 
113 104 104 104 
2 1.13 113 173.8 
104 102 55.4 
104 103 101 101 
LOCS 
36 28 123 123 125 69 81 85 39 24 
REPS 
36 28 139 139 141 82 88 97 42 24 
DIFF 
1 2 1.4 1 2 1.8 9 1 2 3 
PR &gt; T 
.022+ 
.000# 
.541 .423 
.017+ 
.000# 
.008# 
.526 
.000# 
.000# 
__________________________________________________________________________ 
STK PLT EAR RT STA STK BRT GRN DRP GLF 
CNT HT HT LDG GRN LDG STK APP EAR SPT 
% MN % MN 
% MN % MN 
% MN 
% MN 
% MN % MN 
% MN ABS 
__________________________________________________________________________ 
TOTAL SUM 
1 102 106 110 96 121 103 106 110 100 5.7 
2 102 99 95 106 103 97 95 95 102 4.5 
LOCS 
151 63 63 30 79 67 16 9 22 20 
REPS 
192 69 69 38 87 73 23 9 24 25 
DIFF 
0 6 15 11 18 7 12 15 2 1.2 
PR &gt; T 
.999 .000# 
.000# 
.006# 
.000# 
.000# 
.004# 
.089* 
.329 .000# 
__________________________________________________________________________ 
NLF SLF ANT HD MDM FUS DIP ECB ECB ECB 
BLT BLT ROT SMT CLN CPX ERS ERS DPE 1LF 2SC 
ABS ABS ABS ABS ABS ABS ABS ABS ABS ABS ABS 
__________________________________________________________________________ 
TOTAL SUM 
1 4.9 4.0 4.5 100.0 
7.5 4.0 5.9 3.3 100.0 
5.0 7.3 
2 5.1 7.0 3.3 100.0 
5.5 4.5 4.4 3.0 100.0 
3.0 4.6 
LOCS 
4 1 2 1 1 2 4 2 1 1 10 
REPS 
8 2 4 4 2 4 7 3 1 1 11 
DIFF 
0.3 3.0 1.3 0.0 2.0 0.5 1.5 0.3 0.0 2.0 2.8 
PR &gt; T 
.391 .344 .500 
.058* 
.500 .001# 
__________________________________________________________________________ 
* = 10% SIG 
+ = 5% SIG 
# = 1% SIG 
TABLE 2B 
__________________________________________________________________________ 
HYBRID COMISON REPORT 
VARIETY #1 = 33Y18 
VARIETY #2 = 3394 
__________________________________________________________________________ 
PRM BU BU TST SDG EST GDU 
PRM SHD ACR ACR MST WT VGR CNT SHD 
ABS ABS ABS % MN 
% MN 
ABS % MN 
% MN 
% MN 
__________________________________________________________________________ 
TOTAL SUM 
1 112 115 177.2 
105 100 57.3 
113 104 104 
2 109 112 164.3 
97 92 56.0 
129 102 101 
LOCS 
37 29 133 133 135 69 82 84 40 
REPS 
37 29 155 155 157 81 91 95 44 
DIFF 
3 3 12.9 
8 8 1.3 16 2 3 
PR &gt; T 
.000# 
.000# 
.000# 
.000# 
.000# 
.000# 
.000# 
.130 
.000# 
__________________________________________________________________________ 
GDU STK PLT EAR RT STA STK BRT GRN 
SLK CNT HT HT LDG GRN LDG STK APP 
% MN 
% MN 
% MN 
% MN 
% MN 
% MN 
% M % MN 
% MN 
__________________________________________________________________________ 
TOTAL SUM 
1 104 102 106 110 96 123 104 107 110 
2 100 101 95 98 106 80 99 99 101 
LOCS 
25 153 64 64 36 83 72 15 9 
REPS 
26 193 72 72 48 93 83 21 9 
DIFF 
4 1 11 12 10 43 4 8 8 
PR &gt; T 
.000# 
.019+ 
.000# 
.000# 
.005# 
.000# 
.020+ 
.049+ 
.113 
__________________________________________________________________________ 
DRP GLF NLF MDM FUS DIP ECB ECB ECB 
EAR SPT BLT CPX ERS ERS DPE 1LF 2SC 
% MN 
ABS ABS ABS ABS ABS ABS ABS ABS 
__________________________________________________________________________ 
TOTAL SUM 
1 100 5.8 5.0 4.5 6.5 4.0 100.0 
5.0 7.3 
2 97 2.1 6.0 3.5 4.0 8.0 100.0 
1.0 4.8 
LOCS 
22 15 1 1 2 1 1 1 10 
REPS 
24 15 2 2 2 1 1 1 11 
DIFF 
2 3.7 1.0 1.0 2.5 4.0 0.0 4.0 2.5 
PR &gt; T 
.306 
.000# .344 .007# 
__________________________________________________________________________ 
* = 10% SIG 
+ = 5% SIG 
# = 1% SIG 
TABLE 2C 
__________________________________________________________________________ 
HYBRID COMISON REPORT 
VARIETY #1 = 33Y18 
VARIETY #2 = 32K61 
__________________________________________________________________________ 
PRM BU BU TST SDG EST GDU GDU 
PRM SHD ACR ACR MST WT VGR CNT SHD SLK 
ABS ABS ABS % MN 
% MN 
ABS % MN 
% MN 
% MN 
% MN 
__________________________________________________________________________ 
TOTAL SUM 
1 113 115 181.5 
105 99 57.5 
111 105 103 104 
2 115 117 170.9 
98 105 57.1 
101 98 105 106 
LOCS 
20 18 72 72 75 41 49 48 23 18 
REPS 
20 18 76 76 79 42 53 53 25 18 
DIFF 
2 2 10.6 
7 6 0.4 11 7 2 2 
PR &gt; T 
.000# 
.000# 
.001# 
.000# 
.000# 
.123 
.009# 
.000# 
.000# 
.000# 
__________________________________________________________________________ 
STK PLT EAR RT STA STK BRT GRN DRP GLF 
CNT HT HT LDG GRN LDG STK APP EAR SPT 
% MN 
% MN 
% MN 
% MN 
% MN 
% MN 
% MN 
% MN 
% MN 
ABS 
__________________________________________________________________________ 
TOTAL SUM 
1 102 106 110 94 110 104 105 115 99 5.4 
2 98 104 101 96 124 105 106 122 101 5.1 
LOCS 
97 46 46 21 49 49 8 4 14 17 
REPS 
123 51 51 21 54 53 13 4 15 22 
DIFF 
4 2 9 1 14 0 1 8 1 0.4 
PR &gt; T 
.000# 
.009# 
.000# 
.811 
.002# 
.999 
.176 
.186 
.435 
.061* 
__________________________________________________________________________ 
NLF SLF ANT HD MDM FUS DIP ECB ECB 
BLT BLT ROT SMT CLN CPX ERS ERS 1LF 2SC 
ABS ABS ABS ABS ABS ABS ABS ABS ABS ABS 
__________________________________________________________________________ 
TOTAL SUM 
1 4.9 4.0 4.5 100.0 
7.5 4.0 5.8 3.3 5.0 7.8 
2 4.5 7.0 4.5 100.0 
5.0 2.8 5.7 4.8 6.0 6.4 
LOCS 
4 1 2 1 1 2 3 2 1 5 
REPS 
8 2 4 4 2 4 4 3 1 5 
DIFF 
0.4 3.0 0.0 0.0 2.5 1.3 0.2 1.5 1.0 1.4 
PR &gt; T 
.215 .999 .344 
.808 
.205 .052* 
__________________________________________________________________________ 
* = 10% SIG 
+ = 5% SIG 
# = 1% SIG 
Strip Test Data for Hybrid 33Y18 
Comparison data was collected from strip tests that were g by farmers. Each 
hybrid was grown in strips of 4, 6, 8, 12, etc. rows in fields depending 
on the size of the planter used. The data was collected from strip tests 
that had the hybrids in the same area and weighed. The moisture percentage 
was determined and bushels per acre was adjusted to 15.5 percent moisture. 
The number of comparisons represent the number of locations or 
replications for the two hybrids that were grown in the same field in 
close proximity and compared. 
Comparison strip testing was done between Pioneer Brand Hybrid 33Y18 and 
Pioneer Brand Hybrids 3335, 3394, and 32K61. The comparisons come from all 
the hybrid's adapted growing areas in the United States. 
These results are presented in Table 3. The results show Hybrid 33Y18 
demonstrates a significant yield advantage over Hybrid 3394 and shows a 
significant yield advantage in the weighted average for all the comparison 
hybrids. The weighted average yield advantage for all the comparison 
hybrids is 5.2 bushels per acre and ranges from 9.9 to 1.5. Hybrid 33Y18 
demonstrates a significant income advantage to the farmer over Hybrid 3335 
and Hybrid 3394 and shows a significant income advantage in the weighted 
average for all the comparison hybrids. The weighted average adjusted 
gross income advantage for all the hybrids is $16.48 per acre and ranges 
from $26.06 to $9.92. Hybrid 33Y18 shows a significant lower harvest 
moisture advantage over Hybrid 3335 and Hybrid 32K61 and shows a 
significant lower harvest moisture advantage in the weighted average for 
all the comparison hybrids. Hybrid 33Y18 exhibits a significant test 
weight advantage over all three hybrids. The yield and income advantage 
for Hybrid 33Y18 plus its advantage for other characteristics over these 
hybrids will make it an important addition for most of the areas where 
these hybrids are grown. 
TABLE 3 
__________________________________________________________________________ 
1996 PERFORMANCE COMISON REPORT FOR CORN 
1 YEAR SUMMARY OF ALL STANDARD TEST TYPES 
Income/ 
Pop Stand 
Roots 
Test 
Brand Product 
Yield 
Moist 
Acre 
K/Acre 
(%) (%) Wt 
__________________________________________________________________________ 
PIONEER 37Y18 
163.8 
22.6 
468.68 
24.7 
89 84 57.3 
PIONEER 3335 
161.6 
23.8 
458.53 
25.4 
85 91 55.6 
Advantage 2.2 1.2 10.15 
-0.7 
4 -7 1.7 
Number of Comparisons 
108 108 108 79 66 44 99 
Percent Wins 59 69 62 27 60 4 85 
Probability of Difference 
87 99 98 97 99 98 99 
PIONEER 33Y18 
164.3 
22.6 
470.42 
24.7 
89 85 57.2 
PIONEER 3394 
154.4 
21.7 
444.36 
25.1 
90 91 56.1 
Advantage 9.9 -0.9 
26.06 
-0.4 
-1 -6 1.1 
Number of Comparisons 
109 109 109 78 64 42 99 
Percent Wins 72 30 72 41 45 7 74 
Probability of Difference 
99 99 99 82 84 96 99 
PIONEER 33Y18 
156.1 
22.6 
446.55 
24.6 
86 91 57.5 
PIONEER 32K61 
154.6 
24.6 
436.63 
24.9 
92 97 56.8 
Advantage 1.5 2.0 9.92 
-0.3 
-6 -6 0.7 
Number of Comparisons 
55 55 55 45 36 24 53 
Percent Wins 49 90 54 40 33 8 60 
Probability of Difference 
49 99 87 63 96 86 99 
PIONEER 33Y18 
162.5 
22.6 
464.90 
24.7 
88 86 57.3 
WEIGHTED AVG 157.3 
23.1 
448.42 
25.2 
89 92 56.1 
Advantage 5.2 0.5 16.48 
-0.5 
-1 -6 1.2 
Number of Comparisons 
272 272 272 202 166 110 251 
Percent Wins 62 58 64 35 48 6 76 
Probability of Difference 
99 99 99 99 38 99 99 
__________________________________________________________________________ 
NOTE: The probability values are useful in analyzing if there is a "real" 
difference in the genetic potential of the products involved. High values 
are desirable, with 95% considered significant for real differences. 
Comparison of Key Characteristics for Hybrid 33Y18 
Characteristics of Pioneer Hybrid 33Y18 are compared to Pioneer Hybrids 
3335, 3394, and 32K61 in Table 4. Table 4 shows that Hybrid 33Y18 exhibits 
excellent yield ability. Hybrid 33Y18 presents outstanding resistance to 
stalk lodging and shows better resistance to stalk lodging than Hybrid 
3335 and Hybrid 3394. Hybrid 33Y18 also demonstrates exceptional stay 
green and shows a better stay green score than Hybrid 3335 and Hybrid 
3394. Hybrid 33Y18 exhibits a very good test weight rating, which is 
higher than the test weight rating for Hybrid 3335 and Hybrid 3394. Hybrid 
33Y18 shows an above average early growth value. Hybrid 33Y18 exhibits a 
higher plant and ear height than all three of the comparison hybrids. 
Hybrid 33Y18 shows a very good brittle stalk value, which is better than 
all three of the comparison hybrids. Hybrid 33Y18 presents a very good 
value for resistance to Gray Leaf Spot, which is better than the 
resistance values shown for Hybrid 3335 and Hybrid 3394. Hybrid 33Y18 also 
demonstrates a superior value for resistance to second generation European 
Corn Borer feeding, which is better than the resistance values for all 
three of the comparison hybrids. The excellent yield shown by Hybrid 
33Y18, combined with its other favorable agronomic characteristics should 
make it an important hybrid in its area of adaptation. 
TABLE 4 
__________________________________________________________________________ 
Hybrid Patent Comparison-Characteristics 
Pioneer Hybrid 33Y18 vs. Pioneer Hybrids 3335, 3394 and 
__________________________________________________________________________ 
32K61 
SILK 
PHY 
GDU 
GDU STA 
TST 
VARIETY 
RM CRM 
CRM 
SILK 
PHY 
YLD 
H/POP 
L/POP 
SIL 
R/L GRN 
WT 
__________________________________________________________________________ 
33Y18 
112 
115 
112 
1440 
2710 
9 8 9 8 4 8 7 
3335 113 
113 
114 
1410 
2770 
9 8 9 4 7 7 6 
3394 110 
111 
110 
1390 
2660 
8 8 8 7 7 7 6 
32K61 
114 
116 
114 
1450 
2770 
9 8 8 8 8 
__________________________________________________________________________ 
PLT 
EAR BRT 
HSK 
GLF NLF ANT 
MDM FUS 
ECB 
VARIETY 
E/G 
HT HT D/E 
STK 
CVR 
SPT BLT ROT 
CPX ERS 
25C 
__________________________________________________________________________ 
33Y18 
6 8 8 5 6 4 6 5 4 4 6 6 
3335 5 7 5 6 3 3 5 4 3 4 4 4 
3394 8 5 6 4 4 4 2 5 4 3 4 5 
32K61 
6 7 6 5 3 5 6 5 5 3 5 5 
__________________________________________________________________________ 
INDUSTRIAL APPLICABILITY 
This invention includes hybrid maize seed of 33Y18 and the hybrid maize 
plant produced therefrom. The foregoing was set forth by way of example 
and is not intended to limit the scope of the invention. 
As used herein, the term plant includes plant cells, plant protoplasts, 
plant cell tissue cultures from which maize plants can be regenerated, 
plant calli, plant clumps, and plant cells that are intact in plants, or 
parts of plants, such as embryos, pollen, ovules, flowers, kernels, ears, 
cobs, leaves, seeds, husks, stalks, roots, root tips, anthers, silk and 
the like. 
Duncan, Williams, Zehr, and Widholm, Planta, (1985) 165:322-332 reflects 
that 97% of the plants cultured which produced callus were capable of 
plant regeneration. Subsequent experiments with both inbreds and hybrids 
produced 91% regenerable callus which produced plants. In a further study 
in 1988, Songstad, Duncan & Widholm in Plant Cell Reports (1988), 
7:262-265 reports several media additions which enhance regenerability of 
callus of two inbred lines. Other published reports also indicated that 
"nontraditional" tissues are capable of producing somatic embryogenesis 
and plant regeneration. K. P. Rao, et al., Maize Genetics Cooperation 
Newsletter, 60:64-65 (1986), refers to somatic embryogenesis from glume 
callus cultures and B. V. Conger, et al., Plant Cell Reports, 6:345-347 
(1987) indicates somatic embryogenesis from the tissue cultures of maize 
leaf segments. Thus, it is clear from the literature that the state of the 
art is such that these methods of obtaining plants are, and were, 
"conventional" in the sense that they are routinely used and have a very 
high rate of success. 
Tissue culture of maize is described in European Patent Application, 
publication 160,390, incorporated herein by reference. Maize tissue 
culture procedures are also described in Green and Rhodes, "Plant 
Regeneration in Tissue Culture of Maize," Maize for Biological Research 
(Plant Molecular Biology Association, Charlottesville, Va. 1982, at 
367-372) and in Duncan, et al., "The Production of Callus Capable of Plant 
Regeneration from Immature Embryos of Numerous Zea mays Geneotypes," 165 
Planta 322-332 (1985). Thus, another aspect of this invention is to 
provide cells which upon growth and differentiation produce maize plants 
having the genotype of 33Y18. 
Maize is used as human food, livestock feed, and as raw material in 
industry. The food uses of maize, in addition to human consumption of 
maize kemels, include both products of dry- and wet-milling industries. 
Maize, including both grain and non-grain portions of the plant, is also 
used extensively as livestock feed, primarily for beef cattle, dairy 
cattle, hogs, and poultry. 
Industrial uses of maize include production of ethanol, maize starch in the 
wet-milling industry and maize flour in the dry-milling industry. The 
industrial applications of maize starch and flour are based on functional 
properties, such as viscosity, film formation, adhesive properties, and 
ability to suspend particles. The maize starch and flour have application 
in the paper and textile industries. Other industrial uses include 
applications in adhesives, building materials, foundry binders, laundry 
starches, explosives, oil-well muds, and other mining applications. 
Plant parts other than the grain of maize are also used in industry. Stalks 
and husks are made into paper and wallboard and cobs are used for fuel and 
to make charcoal. 
The seed of the hybrid maize plant and various parts of the hybrid maize 
plant can be utilized for human food, livestock feed, and as a raw 
material in industry. 
Although the foregoing invention has been described in some detail by way 
of illustration and example for purposes of clarity and understanding, it 
will be obvious that certain changes and modifications may be practiced 
within the scope of the invention, as limited only by the scope of the 
appended claims. 
DEPOSITS 
Applicant has made a deposit of at least 2500 seeds of Hybrid Maize Line 
33Y18 with the American Type Culture Collection (ATCC), Rockville, Md. 
20852 U.S.A., ATCC Deposit No. 209600. The seeds deposited with the ATCC 
on Jan. 27, 1998 were taken from the deposit maintained by Pioneer Hi-Bred 
International, Inc., 700 Capital Square, 400 Locust Street, Des Moines, 
Iowa 50309-2340 since prior to the filing date of this application. This 
deposit of the Hybrid Maize Line 33Y18 will be maintained in the ATCC 
depository, which is a public depository, for a period of 30 years, or 5 
years after the most recent request, or for the enforceable life of the 
patent, whichever is longer, and will be replaced if it becomes nonviable 
during that period. Additionally, Applicant has satisfied all the 
requirements of 37 C.F.R. .sctn..sctn.1.801-1.809, including providing an 
indication of the viability of the sample. Applicant imposes no 
restrictions on the availability of the deposited material from the ATCC; 
however, Applicant has no authority to waive any restrictions imposed by 
law on the transfer of biological material or its transportation in 
commerce. Applicant does not waive any infringement of its rights granted 
under this patent.