Hybrid maize plant and seed (39B42)

According to the invention, there is provided a hybrid maize plant, designated as 39B42, produced by crossing two Pioneer Hi-Bred International, Inc. proprietary inbred maize lines. This invention relates to the hybrid seed 39B42, the hybrid plant produced from the seed, and variants, mutants, and trivial modifications of hybrid 39B42.

FIELD OF THE INVENTION 
This invention is in the field of maize breeding, specifically relating to 
a hybrid maize line designated 39B42. 
BACKGROUND OF THE INVENTION 
Plant Breeding 
Field crops are bred through techniques that take advantage of the plant's 
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: 
Parent1 AbCdeF/AbCdeF 
Parent2 aBcDEf/aBcDEf 
the F.sub.1 from a cross between these two parents is: 
F.sub.1 AbCdeF/aBcDEf 
Selfing F.sub.1 will produce an F.sub.2 generation including the following 
genotypes: 
##STR1## 
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, Amel 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 
segregating 
alleles in Parents 
favorable alleles in 
Probability that 
loci (n) 
(n/2) new inbred genotype 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 39B42, produced by crossing two Pioneer Hi-Bred 
International, Inc. proprietary inbred maize lines. This invention thus 
relates to the hybrid seed 39B42, the hybrid plant produced from the seed, 
and variants, mutants and trivial modifications of hybrid 39B42. This 
hybrid maize plant is characterized by excellent silage yield for its 
maturity and good silage frame. Hybrid 39B42 demonstrates good root 
lodging resistance and good stay green. 
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. 
ADF RWH=PERCENT ACID DETERGENT FIBER. This is the percent of dry matter 
that is acid detergent fiber in chopped whole plant forage, which is a 
measure of fiber content. 
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 HTM=EAR HEIGHT. Ear height expressed in decimeters. 
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 21T=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 (Ostrinia 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 moniliforrne 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. 
GEN APP=GENERAL APPEARANCE. General appearance score is a 1-9 score 
reflecting the general appearance of hybrids. For silage hybrids, taller, 
leafy, and dark green color would contribute to a higher score. 
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). A 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 1 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 (Helminthosporum 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 (Helminthosporum 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. 
PLT HTM=PLANT HEIGHT. Plant height expressed in decimeters. 
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 
300 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. 
SIL DMP=SILAGE DRY MATTER. The percent of dry material in chopped whole 
plant silage. 
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. 
STR RWH=PERCENT OF STARCH. This is the percent of dry matter that is starch 
in chopped whole plant forage as predicted by Near Infrared Spectroscopy. 
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. 
TDM/HA=TOTAL DRY MATTER/HECTARE. Yield of total dry plant material in 
metric tons per hectare. 
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 I 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.