Inbred corn line PHTM9

According to the invention, there is provided an inbred corn line, designated PHTM9. This invention thus relates to the plants and seeds of inbred corn line PHTM9 and to methods for producing a corn plant produced by crossing the inbred line PHTM9 with itself or with another corn plant. This invention further relates to hybrid corn seeds and plants produced by crossing the inbred line PHTM9 with another corn line or plant.

FIELD OF THE INVENTION 
This invention is in the field of corn breeding, specifically relating to 
an inbred corn line designated PHTM9. 
BACKGROUND OF THE INVENTION 
The goal of plant breeding is to combine in a single variety or hybrid 
various desirable traits. For field crops, these traits may include 
resistance to diseases and insects, tolerance to heat and drought, 
reducing the time to crop maturity, greater yield, and better agronomic 
quality. With mechanical harvesting of many crops, uniformity of plant 
characteristics such as germination and stand establishment, growth rate, 
maturity, and plant and fruit height, is important. 
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 
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. 
Corn plants (Zea mays L.) can be bred by both self-pollination and 
cross-pollination techniques. Corn has separate male and female flowers on 
the same plant, located on the tassel and the ear, respectively. Natural 
pollination occurs in corn when wind blows pollen from the tassels to the 
silks that protrude from the tops of the incipient ears. 
The development of corn hybrids requires the development of homozygous 
inbred lines, the crossing of these lines, and the evaluation of the 
crosses. Pedigree breeding and recurrent selection breeding methods are 
used to develop inbred lines from breeding populations. 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 selling 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. 
Pedigree breeding starts with the crossing of two genotypes, each of which 
may have one or more desirable characteristics that is lacking in the 
other or which complement the other. If the two original parents do not 
provide all of the desired characteristics, other sources can be included 
in the breeding population. In the pedigree method, superior plants are 
selfed and selected in successive generations. In the succeeding 
generations the heterozygous condition gives way to homogeneous lines as a 
result of self-pollination and selection. Typically in the pedigree method 
of breeding five or more generations of selfing and selection is 
practiced: F.sub.1 .fwdarw.F.sub.2 ; F.sub.2 .fwdarw.F.sub.3 ; F.sub.3 
.fwdarw.F.sub.4 ; F.sub.4 .fwdarw.F.sub.5, etc. 
Backcrossing can be used to improve an inbred line. Backcrossing transfers 
a specific desirable trait from one inbred or source to an inbred that 
lacks that trait. This can be accomplished for example by first crossing a 
superior inbred (A) (recurrent parent) to a donor inbred (non-recurrent 
parent), which carries the appropriate gene(s) for the trait in question. 
The progeny of this cross is then mated back to the superior recurrent 
parent (A) followed by selection in the resultant progeny for the desired 
trait to be transferred from the non-recurrent parent. After five or more 
backcross generations with selection for the desired trait, the progeny 
will be heterozygous for loci controlling the characteristic being 
transferred, but will be like the superior parent for most or almost all 
other genes. The last backcross generation would be selfed to give pure 
breeding progeny for the gene(s) being transferred. 
A single cross hybrid corn variety is the cross of two inbred lines, each 
of which has a genotype which complements the genotype of the other. The 
hybrid progeny of the first generation is designated F.sub.1. In the 
development of hybrids only the F.sub.1 hybrid plants are sought. 
Preferred F.sub.1 hybrids are more-vigorous than their inbred parents. 
This hybrid vigor, or heterosis, can be manifested in many polygenic 
traits, including increased vegetative growth and increased yield. 
The development of a hybrid corn variety involves three steps: (1) the 
selection of plants from various germplasm pools; (2) the selfing of the 
selected plants 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 corn, the vigor of the lines decreases. Vigor is 
restored when two unrelated 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 between any two inbreds 
will always be the same. Once the inbreds that give a superior hybrid have 
been identified, the hybrid seed can be reproduced indefinitely as long as 
the homogeneity of the inbred parents is maintained. 
A single cross hybrid is produced when two inbred lines are crossed to 
produce the F.sub.1 progeny. A double cross hybrid is produced from four 
inbred lines crossed in pairs (A x B and C x D) and then the two F.sub.1 
hybrids are crossed again (A x B) x (C x D). Much of the hybrid vigor 
exhibited by F.sub.1 hybrids is lost in the next generation (F.sub.2). 
Consequently, seed from hybrid varieties is not used for planting stock. 
Corn is an important and valuable field crop. Thus, a continuing goal of 
plant breeders is to develop high-yielding corn hybrids that are 
agronomically sound based on stable inbred lines. The reasons for this 
goal are obvious: to maximize the amount of grain produced with the inputs 
used and minimize susceptibility of the crop to environmental stresses. To 
accomplish this goal, the corn breeder must select and develop superior 
inbred parental lines for producing hybrids. This requires identification 
and selection of genetically unique individuals which in a segregating 
population occur as the result of a combination of crossover events plus 
the independent assortment of specific combinations of alleles at many 
gene loci which results in specific genotypes. Based on the number of 
segregating genes, the frequency of occurrence of an individual with a 
specific genotype is less than 1 in 10,000. Thus, even if the entire 
genotype of the parents has been characterized and the desired genotype is 
known, only a few if any individuals having the desired genotype may be 
found in a large F.sub.2 or S.sub.0 population. Typically, however, the 
genotype of neither the parents nor the desired genotype is known in any 
detail. 
At Pioneer Hi-Bred International, a typical corn research station has a 
staff of four, and 20 acres of breeding nursery. Those researchers plant 
those 20 acres with 25,000 nursery rows, 15,000 yield test plots in 10-15 
yield test sites, and one or two disease-screening nurseries. Employing a 
temporary crew of 20 to 30 pollinators, the station makes about 65,000 
hand pollinations per growing season, and produces from three to ten new 
inbreds which are proposed for commercial use each year. Over the 32 
Pioneer research stations in North America, this amounts to from about 100 
to 300 new inbreds proposed each year from over 2,000,000 pollinations. Of 
those, less than 50 and more commonly less than 30 are actually selected 
for commercial use. 
SUMMARY OF THE INVENTION 
According to the invention, there is provided a novel inbred corn line, 
designated PHTM9. This invention thus relates to the seeds of inbred corn 
line PHTM9, to the plants of inbred corn line PHTM9, and to methods for 
producing a corn plant produced by crossing the inbred line PHTM9 with 
itself or another corn line. This invention further relates to hybrid corn 
seeds and plants produced by crossing the inbred line PHTM9 with another 
corn line. 
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. ABS is in absolute terms and % MN is 
percent of the mean for the experiments in which the inbred or hybrid was 
grown. 
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. 
BU ACR=YIELD (BUSHELS/ACRE). Actual yield of the grain at harvest in 
bushels per acre adjusted to 15.5% moisture. 
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. 
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. 
EAR SZ=EAR SIZE. A 1 to 9 visual rating of ear size. The higher the rating 
the larger the ear size. 
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 a per plot 
basis for the inbred or hybrid. 
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. 
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 the harvested grain, any mold on the grain, and any 
cracked grain. High scores indicate good grain quality. 
MST=HARVEST MOISTURE. The moisture is the actual percentage moisture of the 
grain at harvest. 
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. 
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 factors, be produced in a cytoplasmic male-sterile form 
which is otherwise phenotypically identical to the male-fertile form. 
PRM=PREDICTED RM. This trait, predicted relative maturity (RM), 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 
which is similar to the Minnesota Relative Maturity Rating System. 
RT LDG=ROOT LODGING. Root lodging is the percentage of plants that do not 
root lodge; plants that lean from the vertical axis at an approximately 
30.degree. angle or greater would be counted as root lodged. 
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 corn 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. 
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. 
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. 
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 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). 
TILLER=TILLERS. A count of the number of tillers per plot that could 
possibly shed pollen was taken. Data is given as percentage of tillers: 
number of tillers per plot divided by number of plants per plot. 
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 percent moisture. 
YLD=YIELD. It is the same as BU ACR ABS. 
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. 
MDM CPX=Maize Dwarf Mosaic Complex (MDMV=Maize Dwarf Mosaic Virus & 
MCDV=Maize Chlorotic Dwarf Virus): Visual rating (1-9 score) where a "1" 
is very susceptible and a "9" is very resistant. 
SLF BLT=Southern Leaf Blight (Bipolaris maydis, Helminthosporium maydis): 
Visual rating (1-9 score) where a "1" is very susceptible and a "9" is 
very resistant. 
NLF BLT=Northern Leaf Blight (Exserohilum turcicum, H. turcicum): Visual 
rating (1-9 score) where a "1" is very susceptible and a "9" is very 
resistant. 
COM RST=Common Rust (Puccinia sorghi): Visual rating (1-9 score) where a 
"1" is very susceptible and a "9" is very resistant. 
GLF SPT=Gray Leaf Spot (Cercospora zeae-maydis): Visual rating (1-9 score) 
where a "1" is very susceptible and a "9" is very resistant. 
STW WLT=Stewart's Wilt (Erwinia stewartii): Visual rating (1-9 score) where 
a "1" is very susceptible and a "9" is very resistant. 
HD SMT=Head Smut (Sphacelotheca reiliana): Percentage of plants that did 
not have infection. 
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 specific mold organism, 
and may not be predictive for a specific ear mold. 
ECB DPE=Dropped ears due to European Corn Borer (Ostrinia nubilalis): 
Percentage of plants that did not drop ears under second brood corn borer 
infestation. 
ECB 2SC=European Corn Borer Second Brood (Ostrinia nubilalis): Visual 
rating (1-9 score) of post flowering damage due to infestation by European 
Corn Borer. A "1" is very susceptible and a "9" is very resistant. 
ECB 1LF=European Corn Borer First Brood (Ostrinia nubilalis): Visual rating 
(1-9 score) of pre-flowering leaf feeding by European Corn Borer. A "1" is 
very susceptible and a "9" is very resistant.