Inbred corn line PHN73
FIELD OF THE INVENTION 
     This invention is in the field of corn breeding, specifically relating to an inbred corn line designated PHN73. 
     BACKGROUND OF THE INVENTION 
     The goal of plant breeding is to combine in a single variety/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 fruit size, is important. 
     Field crops are bred through techniques that take advantage of the plant&#39;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 produce 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 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. 
     Pedigree breeding for single-gene traits 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 1  --→F 2  ; F 2  --→F 3  ; F 3  --→F 4  ; F 4  --→F 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 1 . In the development of hybrids only the F 1  hybrid plants are sought. Preferred F 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, each breed true and are highly uniform; and (3) crossing the selected inbred lines with unrelated inbred lines to produce the hybrid progeny (F 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 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 progeny. A double cross hybrid is produced from four inbred lines crossed in pairs (A×B and C×D) and then the two F 1  hybrids are crossed again (A×B)×(C×D). Much of the hybrid vigor exhibited by F 1  hybrids is lost in the next generation (F 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 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 2  or S 0  population. Typically, however, the genotype of neither the parents nor the desired genotype is known in any detail. 
     SUMMARY OF THE INVENTION 
     According to the invention, there is provided a novel inbred corn line, designated PHN73. This invention thus relates to the seeds of inbred corn line PHN73, to the plants of inbred corn line PHN73, and to methods for producing a corn plant produced by crossing the inbred line PHN73 with itself or another corn line. This invention further relates to hybrid corn seeds and plants produced by crossing the inbred line PHN73 with another corn line or a related species. 
     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: 
     BAR PLT=BARREN PLANTS. This is the number 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 adjusted to 15.5% moisture. ABS is in absolute terms and % MN is percent of the mean for the experiments in which the inbred or hybrid was grown. 
     CLD TST=COLD TEST. This is the percentage of kernels that germinate under cold soil conditions. ABS=absolute measurement and % MN is percentage of mean of the experiments in which inbred or hybrid was grown. 
     COB SC=COB SCORE. The cob score is a rating of how well the grain is shelled off the cob and how badly the cob is broken up going through the combine. This is given as a 1 to 9 score with 9 being very good. A high score indicates that the grain shells off of the cob well, and the cob does not break. 
     DRP EAR=DROPPED EARS. This is 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 top 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° F. and the lowest minimum temperature used is 50° 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 QUL=GRAIN QUALITY. This is a 1 to 9 rating for the general quality 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. 
     KER LB=KERNELS PER POUND. This is the number of kernels per 0.1 pound. 
     KSZ L=KERNEL SIZE LARGE. Percentage by weight of shelled corn that passes through a screen with 25/64 inch diameter openings but does not pass through a screen with 22/64 inch diameter openings. 
     KSZ MF=KERNEL SIZE MEDIUM FLAT. Percentage by weight of shelled corn that passes through a screen with 22/64 inch diameter openings and a screen with 13/64 inch wide slot screen but does not pass through a screen with 18.5/64 inch diameter openings. 
     KSZ MR=KERNEL SIZE MEDIUM ROUND. Percentage by weight of shelled corn that passes through a screen with 22/64 inch diameter openings but does not pass through a 13/64 inch wide slot screen or a screen with 18.5/64 inch diameter openings. 
     KSZ S=KERNEL SIZE SMALL. Percentage by weight of shelled corn that passes through a screen with 18.5/64 inch diameter openings but does not pass through a screen with 16/64 inch diameter openings. 
     KSZ TIP=KERNEL SIZE TIPS. Percentage by weight of shelled corn that passes through a screen with 16/64 inch diameter openings. 
     KSZ XL=KERNEL SIZE EXTRA LARGE. Percentage by weight of shelled corn that does not pass through a screen with 25/64 inch diameter openings. 
     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 WT=POLLEN WEIGHT. This is the weight of pollen per 100 plants taken on a plot basis. ABS refers to data in absolute, and % MN refers to data presented as percentage of experimental mean. 
     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 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° 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&#39;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. 
     CLN=Corn Lethal Necrosis (MCMV=Maize Chlorotic Mottle Virus and MDMV™Maize Dwarf Mosaic Virus): Visual rating (1-9 score) where a &#34;1&#34; is very susceptible and a &#34;9&#34; is very resistant. 
     MDM CPX=Maize Dwarf Mosaic Complex (MDMV™Maize Dwarf Mosaic Virus &amp; MCDV=Maize Chlorotic Dwarf Virus): Visual rating (1-9 score) where a &#34;1&#34; is very susceptible and a &#34;9&#34; is very resistant. 
     COM SMT=Common Smut (Ustilago maydis): Percentage of plants that did not have infection. 
     ANT ROT Anthracnose Stalk Rot (Colletotrichum graminicola): Visual rating (1-9 score) where a &#34;1&#34; is very susceptible and a &#34;9&#34; is very resistant. 
     SLF BLT Southern Leaf Blight (Bipolaris maydis, Helminthosporium maydis): Visual rating (1-9 score) where a &#34;1&#34; is very susceptible and a &#34;9&#34; is very resistant. 
     NLF BLT=Northern Leaf Blight (Exserohilum turcicum, H. turcicum): Visual rating (1-9 score) where a &#34;1&#34; is very susceptible and a &#34;9&#34; is very resistant. 
     HC BLT =Helminthosporium Carbonum Leaf Blight (Bipolariszeicola, H. carbonum): Visual rating (1-9 score) where a &#34;1&#34; is very susceptible and a &#34;9&#34; is very resistant. 
     COM RST=Common Rust (Puccinia sorghi): Visual rating (1-9 score) where a &#34;1&#34; is very susceptible and a &#34;9&#34; is very resistant. 
     SO RST =Southern Rust (Puccinia polysora): Visual rating (1-9 score) where a &#34;1&#34; is very susceptible and a &#34;9&#34; is very resistant. 
     EYE SPT=Eyespot (Kabatiella zeae): Visual rating (1-9 score) where a &#34;1&#34; is very susceptible and a &#34;9&#34; is very resistant. 
     GLF SPT=Gray Leaf Spot (Cercospora zeae-maydis): Visual rating (1-9 score) where a &#34;1&#34; is very susceptible and a &#34;9&#34; is very resistant. 
     STW WLT=Stewart&#39;s Wilt (Erwinia stewartii): Visual rating (1-9 score) where a &#34;1&#34; is very susceptible and a &#34;9&#34; is very resistant. 
     GOS WLT=Goss&#39;s Wilt (Corynebacterium nebraskense): Visual rating (1-9 score) where a &#34;1&#34; is very susceptible and a &#34;9&#34; is very resistant. 
     HD SMT=Head Smut (Spacelotheca reiliana): Percentage of plants that did not have infection. 
     DNY MIL=Downy Mildew (Peronosclerospora sorghi): Percentage of plants that did not have infection. 
     FUS EAR=Fusarium Ear Mold (Fusarium moniliforme): Percentage of plants that did not have infection. 
     EAR MLD=General Ear Mold: Visual rating (1-9 score) where a &#34;1&#34; is very susceptible and a &#34;9&#34; 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 &#34;1&#34; is very susceptible and a &#34;9&#34; 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 &#34;1&#34; is very susceptible and a &#34;9&#34; is very resistant. 
     ECB 2IT=European Corn Borer Second Brood Tunneling (Ostrinia nubilalis): The average inches of tunneling in the stalk due to second brood (post-flowering) European Corn Borer infestation. Determined by splitting stalks with a knife, from four internodes above the ear to the ground. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Inbred Corn Line PHN73 is a yellow, dent corn inbred with superior characteristics and provides an acceptable male parental line in crosses for producing first generation F 1  corn hybrids. This inbred is adapted over most regions of the U.S.A. The inbred can be used to produce hybrids from approximately 100-115 relative maturity based on the Minnesota Relative Maturity Rating System for harvest moisture of grain. PHN73 should not be used as a female parent because of low yield and poor cold test. PHN73 was 100% of the experimental mean for amount of pollen in the pollen yield test averaged over 13 locations. 
     The inbred has shown uniformity and stability within the limits of environmental influence for all the traits as described in the Variety Description Information (Table 1) that follows. Most of the data in the Variety Description Information was collected at Johnston, IW. The inbred has been self-pollinated and ear-rowed a sufficient number of generations with careful attention paid to uniformity of plant type to ensure homozygosity and phenotypic stability. The line has been increased both by hand and in isolated fields with continued observation for uniformity. No variant traits have been observed or are expected in PHN73. 
     Inbred corn line PHN73, being substantially homozygous, can be reproduced by planting seeds of the line, growing the resulting corn plants under self-pollinating or sib-pollinating conditions with adequate isolation, and harvesting the resulting seed, using techniques familiar to the agricultural arts. 
     
                       TABLE 1                                                     
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PHN73                                                                     
VARIETY DESCRIPTION INFORMATION                                           
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Type: Dent   Region Best Adapted: Most Regions                            
A.    Maturity: Averaged across maturity zones. Zone: 0                   
      INBRED = PHN73                                                      
      Heat Unit Shed: 1450                                                
      Heat Unit Silk: 1470                                                
      No. Reps:  69                                                       
       ##STR1##                                                           
*     If maximum is greater than 86 degrees fahrenheit, then 86           
      is used and if minimum is less than 50, then 50 is Heat             
      units accumulated daily and can not be less than 0.                 
B.    Plant Characteristics:                                              
      Plant height (to tassel tip): 219 cm                                
      Length of top ear internode: 12 cm                                  
      Number of ears per stalk: Single ear                                
      Ear height (to base of top ear): 82 cm                              
      Number of tillers: None                                             
      Cytoplasm type: Normal                                              
C.    Leaf:                                                               
      Color: (HY) Light green                                             
      Angle from Stalk: 30-60 degrees                                     
      Marginal Waves: (OH7L) Many                                         
      Number of Leaves (mature plants): 18                                
      Sheath Pubescence: (W22) Light                                      
      Longitudinal Creases: (OH56A) Few                                   
      Length (Ear node leaf): 70 cm                                       
      Width (widest point, ear node leaf): 8 cm                           
D     Tassel:                                                             
      Number lateral branches: 5                                          
      Branch Angle from central spike: 30-40 degrees                      
      Pollen Shed: Medium based on pollen yield test (100% of             
      experiment mean).                                                   
      Peduncle Length (top leaf to basal branches): 23 cm                 
      Anther Color: Yellow                                                
      Glume Color: Green                                                  
E.    Ear (Husked Ear Data Except When Stated Otherwise):                 
      Length: 17 cm                                                       
      Weight: 93 gm                                                       
      Mid-point Diameter: 39 mm                                           
      Silk Color: Green                                                   
      Husk Extension (Harvest stage): Long (8-10 cm beyond                
      ear tip)                                                            
      Husk Leaf: Long (&gt;5 cm)                                             
      Taper of Ear: Slight taper                                          
      Position of Shank (dry husks): Drooping                             
      Kernel Rows: Distinct, straight, Number = 14                        
      Husk Color (fresh): Light green                                     
      Husk Color (dry): Buff                                              
      Shank Length: 15 cm                                                 
      Shank (No. of internodes): 8                                        
F.    Kernel (Dried):                                                     
      Size (from ear mid-point)                                           
        Length: 10 mm                                                     
        Width: 9 mm                                                       
        Thick: 5 mm                                                       
      Shape Grade (% rounds): 20-40% medium rounds base                   
      on Parent Test.                                                     
      Pericarp Color: Colorless                                           
      Aleurone Color: Homozygous yellow                                   
      Endosperm Color: Yellow                                             
      Endosperm Type: Normal                                              
      Gm Wt/100 Seeds (unsized): 29 gm                                    
G.    Cob:                                                                
      Diameter at mid-point: 25 mm                                        
      Strength: Strong                                                    
      Color: White                                                        
H.    Diseases:                                                           
      Corn Lethal Necrosis (MCMV = Maize Chlorotic                        
      Mottle Virus and MDMV = Maize Dwarf Mosaic                          
      Virus): Intermediate                                                
      Maize Dwarf Mosaic Complex (MDMV &amp;                                  
      MCDV = Maize Chlorotic Dwarf Virus): Susceptible                    
      Anthracnose Stalk Rot (C. Graminicola): Intermediate                
      S. Leaf Blight (H. Maydis): Intermediate                            
      N. Leaf Blight (H. Turcicum): Intermediate                          
      Carbonum Leaf Blight (H. Carbonum): Resistant                       
      Common Rust (P. Sorghi): Intermediate                               
      Eye Spot (K. Zeae): Intermediate                                    
      Gray Leaf Spot (C. Zeae): Intermediate                              
      Stewarts Wilt (E. Stewatii): Resistant                              
      Goss&#39;s Wilt (C. Nebraskense): Intermediate                          
      Common Smut (U. Maydis): Resistant                                  
      Head Smut (S. Reiliana): Intermediate                               
      Downy Mildew (S. Sorghi): Resistant                                 
      Fusarium Ear Mold (F. Moniliforme): Susceptible                     
I.    Insects:                                                            
      European Corn Borer-1 Leaf Damage (Pre-flowering):                  
      Susceptible                                                         
      European Corn Borer-2 (Post-flowering): Intermediate                
J.    Variety Most Closely Resembling:                                    
      Character    Inbred                                                 
      Maturity G50                                                        
      Usage G35                                                           
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     PHG50 (PVP Certificate No. 8300143) and PHG35 (PVP Certificate No. 8033140) are Pioneer proprietary inbreds. PHN73 is closer genetically and is usages to G35 and G50. 
     Data for items B, C, D, E, F, and G are primarily based on a maximum of three reps of data grown at Johnston, Iowa in 1987 and 1988, plus description information from the maintaining station. 
     
                       TABLE 2                                                     
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ELECTROPHORESIS RESULTS                                                   
Isozyme Genotypes for PHN73                                               
Isozyme data was generated for inbred corn line PHN73                     
according to the procedure described in Goodmam, M.M. and                 
Stuber, C.M., &#34;Genetic indentification of lines and crosses               
using isoenzyme electrophoresis,&#34; Proceedings of the Thirty-              
Fifth Annual Corn and Sorghum Industry Research Conference,               
Chicago, Illinois (1980).                                                 
Alleles Present                                                           
        Loci  PHN73                                                       
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        ACP1  4                                                           
        ADH1  4                                                           
        CAT3  N                                                           
        DIA1  8                                                           
        GOT1  4                                                           
        GOT2  4                                                           
        GOT3  4                                                           
        IDH1  4                                                           
        IDH2  6                                                           
        MDH1  6                                                           
        MDH2  6                                                           
        MDH3  16                                                          
        MDH4  12                                                          
        MDH5  12                                                          
        MMM   4                                                           
        PGM1  9                                                           
        PGM2  4                                                           
        PGD1  3.8                                                         
        PGD2  5                                                           
        PHI1  4                                                           
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     INDUSTRIAL APPLICABILITY 
     This invention also is directed to methods for producing a corn plant by crossing a first parent corn plant with a second parent corn plant wherein the first or second parent corn plant is an inbred corn plant from the line PHN73. Further, both first and second parent corn plants can come from the inbred corn line PHN73. Thus, any such methods using the inbred corn line PHN73 are part of this invention: selfing, backcrosses, hybrid production, crosses to populations, and the like. All plants produced using inbred corn line PHN73 as a parent are within the scope of this invention. Advantageously, the inbred corn line is used in crosses with other, different, corn inbreds to produce first generation (F 1 ) corn hybrid seeds and plants with superior characteristics. 
     As used herein, the terms &#34;plant and plant parts&#34; include plant cells, plant protoplasts, plant cell tissue culture from which corn plants can be regenerated, plant calli, plant clumps, and plant cells that are intact in plants or parts of plants, such as embryos, pollen, flowers, kernels, ears, cobs, leaves, husks, stalks, roots, root tips, anthers, silk and the like. 
     Tissue culture of corn is described in European Patent Application, publication 160,390, incorporated herein by reference. Corn tissue culture procedures are also described in Green and Rhodes, &#34;Plant Regeneration in Tissue Culture of Maize,&#34; Maize for Biological Research (Plant Molecular Biology Association, Charlottsville, VA 1982, at 367-372. Thus, another aspect of this invention is to provide cells which upon growth and differentiation produce the inbred line PHN73. 
     The utility of inbred line PHN73 also extends to crosses with other species. Commonly, suitable species will be of the family Graminaceae, and especially of the genera Zea, Tripsacum, Coix, Schlerachne, Polytoca, Chionachne, and Trilobachne, of the tribe Maydeae. Of these, Zea and Tripsacum, are most preferred. Potentially suitable for crosses with PHN73 may be the various varieties of grain sorghum, Sorghum bicolor (L.) Moench. 
     Corn is used as human food, livestock feed, and as raw material in industry. The food uses of corn, in addition to human consumption of corn kernels, include both products of dry- and wet-milling industries and alkaline cooking. The principal products of corn dry milling are grits, meal and flour. The corn wet-milling industry can provide corn starch, corn syrups, and dextrose for food use. Alkaline cooking provides snack foods (i.e., corn chips, tortillas, etc.) Corn oil is recovered from corn germ, which is a by-product of both dry- and wet-milling industries. 
     Corn, 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 corn are mainly from corn starch from the wet-milling industry and corn flour from the dry-milling industry. The industrial applications of corn starch and flour are based on functional properties, such as viscosity, film formation, adhesive properties, and ability to suspend particles. The corn 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 corn 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 inbred corn line PHN73, the plant produced from the inbred seed, the hybrid corn plant produced from the crossing of the inbred, hybrid seed, and various parts of the hybrid corn plant can be utilized for human food, livestock feed, and as a raw material in industry. 
     EXAMPLE 
     INBRED AND HYBRID PERFORMANCE OF PHN73 
     In the examples that follow the traits and characteristics of inbred corn line PHN73 are given as a line and in hybrid combination. The data collected on inbred corn line PHN73 is presented for the key characteristics and traits. 
     The results in Table 3 compare PHN73 to PHJ35. PHJ35 (PVP Certificate #8300140) is an important inbred that would be used in some of the areas that PHN73 would be used and would cross well with some of the same inbred lines. This data has been collected over four years of research testing. The data shows that the two lines differ significantly for a number of traits. PHN73 is earlier flowering, with harder textured grain, and it has significantly better Northern leaf blight tolerance. PHN73 can be used farther north than PHG35 because of its earlier maturity characteristics. Its harder textured grain plus white cob provides potential for it to be used in early food corn hybrids. 
     The results in Table 4 compare a PHN73 hybrid to Pioneere® brand 3585. Although these hybrids have no parents in common, 3585 is an important hybrid in the area where the PHN73 hybrid is adapted. The data shows that the PHN73 hybrid has higher yield, much better stalk lodging resistance, better stay green, and higher grain test weight with better grain quality. Improved yield performance, grain quality and test weight combined with a white cob make the PHN73 hybrid an attractive hybrid for food corn processors. 
     The results in Table 5 compare a PHN73 hybrid to Pioneer® brand 3475. Although the PHN73 hybrid and 3475 have no parents in common, 3475 is a very significant hybrid sold in the same area where the PHN73 hybrid is adapted. The data shows that the PHN73 hybrid has higher yield with lower harvest moisture, better stalks, better stay green, improved grain quality and fewer dropped ears. These advantages plus its potential use as a food grade hybrid make it a key additional hybrid in the commercial lineup. 
     
                                           TABLE 3                                 
__________________________________________________________________________
PAIRED INBRED COMPARISON DATA                                             
INBRED #1 - PHN73                                                         
INBRED #2 - PHJ35                                                         
__________________________________________________________________________
            BAR BRT EAR EAR   EST   TIL   GDU   GDU   GRN PLT             
        VAR PLT STK HT  SZ    CNT   LER   SHD   SLK   QUL HT              
YEAR    #   ABS ABS ABS ABS   ABS   ABS   ABS   ABS   ABS ABS             
__________________________________________________________________________
TOTAL SUM                                                                 
        1   88.2                                                          
                99.1                                                      
                    27.4                                                  
                        5.2   24.0  18.4  146.0 148.6 6.0 73.0            
        2   85.2                                                          
                96.7                                                      
                    28.4                                                  
                        6.2   25.9  3.0   156.7 159.6 8.0 71.2            
        LOCS                                                              
            9   4   20  17    70    25    59    58    1   21              
        DIFF                                                              
            3.0 2.4 1.1 1.0   1.9   15.4  10.7  11.0  2.0 1.8             
        PROB                                                              
            .106                                                          
                .355                                                      
                    .474                                                  
                        .005# .002# .041+ .000# .000#     .247            
__________________________________________________________________________
            POL   TAS                                                     
                     TAS   TEX   SCT SDG STA  STK   YLD   COM             
        VAR SC    BLS                                                     
                     SZ    EAR   GRN VGR GRN  CNT   SC    RST             
YEAR    #   ABS   ABS                                                     
                     ABS   ABS   ABS ABS ABS  ABS   ABS   ABS             
__________________________________________________________________________
TOTAL SUM                                                                 
        1    4.9  9.0                                                     
                     5.0   6.8   5.7 4.8 6.9  22.1  4.6   5.0             
        2   5.6   9.0                                                     
                     6.3   6.1   5.8 5.0 6.0  23.4  5.7   5.0             
        LOCS                                                              
            37    1  25    13    27  29  9    50    26    2               
        DIFF                                                              
            0.7   0.0                                                     
                     1.4   0.7   0.0 0.1 0.9  1.3   1.1   0.5             
        PROB                                                              
            .003#    .000# .062* .898                                     
                                     .602                                 
                                         .277 .002# .000# .795            
__________________________________________________________________________
                 COM  EAR  ECB   ECB                                      
                                    EYE   GLF                             
                                             NFL   SLF                    
                                                      SO STW              
             VAR SMT  MLD  1LF   2SC                                      
                                    SPT   SPT                             
                                             BLT   BLT                    
                                                      RST                 
                                                         WLT              
             #   ABS  ABS  ABS   ABS                                      
                                    ABS   ABS                             
                                             ABS   ABS                    
                                                      ABS                 
                                                         ABS              
__________________________________________________________________________
TOTAL SUM    1   0.0  4.7  4.7   4.8                                      
                                    3.5   4.0                             
                                             7.3   4.5                    
                                                      5.5                 
                                                         7.5              
             2   0.0  6.5  5.7   6.5                                      
                                    4.5   2.5                             
                                             4.5   6.5                    
                                                      4.0                 
                                                         7.5              
             LOCS                                                         
                 1    23   19    6  2     1  4     1  1  2                
             DIFF                                                         
                 0.0  1.9  1.0   1.7                                      
                                    1.0   1.5                             
                                             2.8   2.0                    
                                                      1.5                 
                                                         0.0              
             PROB     .001#                                               
                           .019+ .141                                     
                                    .000#    .010+       .000#            
__________________________________________________________________________
  *10% SIG                                                                
 + = 5% SIG                                                               
 # = 1% SIG                                                               
 
    
     
                                           TABLE 4                                 
__________________________________________________________________________
#1 - PHN73 HYBRID                                                         
#2 - PIONEER ® 3585                                                   
__________________________________________________________________________
                            BU    BU          GDU   STK                   
              VAR     SEL   ACR   ACR   MST   SHD   LDG                   
YEAR    REGION                                                            
              #   PRM IND   ABS   % MN  ABS   ABS   ABS                   
__________________________________________________________________________
TOTAL SUM     1   109 103   127.3 101   20.0  140.8 94.4                  
              2   108 96    123.7 98    19.7  134.0 89.1                  
              LOCS                                                        
                  20  17    98    98    98    23    92                    
              DIFF                                                        
                  0   7     3.6   4     0.4   6.8   5.3                   
              PROB                                                        
                  .613                                                    
                      .007# .019+ .004# .022+ .000# .000#                 
__________________________________________________________________________
                    RT  BAR   STA   TST   COB GRN   SDG                   
                VAR LDG PLT   GRN   WTA   SC  QUL   VGR                   
YEAR      REGION                                                          
                #   ABS ABS   ABS   ABS   ABS ABS   ABS                   
__________________________________________________________________________
TOTAL SUM       1   97.7                                                  
                        91.6  6.4   57.7  6.5 6.7   5.2                   
                2   98.1                                                  
                        96.0  4.1   57.1  6.0 6.0   6.3                   
                LOCS                                                      
                    31  22    67    97    13  74    61                    
                DIFF                                                      
                    0.4 4.4   2.4   0.6   0.5 0.7   1.2                   
                PROB                                                      
                    .710                                                  
                        .003# .000# .000# .165                            
                                              .000# .000#                 
__________________________________________________________________________
                         EST   STK   PLT   EAR  DRP   BRT                 
                     VAR CNT   CNT   HT    HT   EAR   STK                 
       YEAR    REGION                                                     
                     #   ABS   ABS   ABS   ABS  ABS   ABS                 
__________________________________________________________________________
       TOTAL SUM     1   55.2  46.2  101.8 43.1 99.7  97.8                
                     2   63.0  47.8  99.5  42.3 99.4  96.9                
                     LOCS                                                 
                         72    105   41    41   82    3                   
                     DIFF                                                 
                         7.8   1.6   2.3   0.8  0.3   0.9                 
                     PROB                                                 
                         .000# .001# .001# .065*                          
                                                .012+ .833                
__________________________________________________________________________
 *10% SIG                                                                 
 + = 5% SIG                                                               
 # = 1% SIG                                                               
 
    
     
                                           TABLE 5                                 
__________________________________________________________________________
#1 - PHN73 HYBRID                                                         
#2 - PIONEER ® 3475                                                   
__________________________________________________________________________
                               BU    BU           GDU   STK               
              VAR        SEL   ACR   ACR    MST   SHD   LDG               
YEAR    REGION                                                            
              #   PRM    IND   ABS   % MN   ABS   ABS   ABS               
__________________________________________________________________________
TOTAL SUM     1   109    103   131.5 102    19.8  140.9 93.3              
              2   112    94    127.5 97     20.6  135.2 90.0              
              LOCS                                                        
                  28     24    139   139    140   34    131               
              DIFF                                                        
                  3      9     4.0   5      0.8   5.7   3.3               
              PROB                                                        
                  .000#  .001# .013+ .001#  .000# .000# .000#             
__________________________________________________________________________
                     RT   BAR  STA   TST COB GRN   SDG   EST              
                 VAR LDG  PLT  GRN   WTA SC  QUL   VGR   CNT              
YEAR       REGION                                                         
                 #   ABS  ABS  ABS   ABS ABS ABS   ABS   ABS              
__________________________________________________________________________
TOTAL SUM        1   97.0 92.8 6.2   57.7                                 
                                         6.6 6.8   5.3   55.9             
                 2   97.5 94.9 4.7   57.6                                 
                                         6.5 6.4   5.9   59.9             
                 LOCS                                                     
                     35   29   95    139 14  111   83    106              
                 DIFF                                                     
                     0.5  2.2  1.5   0.1 0.1 0.4   0.6   3.9              
                 PROB                                                     
                     .521 .082*                                           
                               .000# .470                                 
                                         .657                             
                                             .000# .001# .000#            
__________________________________________________________________________
                                   STK   PLT   EAR   DRP   BRT            
                               VAR CNT   HT    HT    EAR   STK            
                 YEAR    REGION                                           
                               #   ABS   ABS   ABS   ABS   ABS            
__________________________________________________________________________
                 TOTAL SUM     1   46.8  100.4 42.7  99.7  98.3           
                               2   48.0  92.7  40.7  99.2  99.2           
                               LOCS                                       
                                   147   64    64    111   5              
                               DIFF                                       
                                   1.1   7.8   2.0   0.5   1.0            
                               PROB                                       
                                   .009# .000# .000# .000# .333           
__________________________________________________________________________
 *10% SIG                                                                 
 + = 5% SIG                                                               
 # = 1% SIG                                                               
 
    
     Applicants have made available to the public without restriction a deposit of at least 2500 seeds of inbred PHN73 with the American Type Culture Collection (ATCC), Rockville, MD 20852 U.S.A., ATCC Deposit No. 75205. The seeds deposited with the ATCC are taken from the same deposit maintained by Pioneer Hi-Bred International Inc., 700 Capital Square, 400 Locust Street, Des Moines, IW 50309 since prior to the filing date of this application. This deposit of the Inbred Corn Line PHN73 will be maintained without restriction 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 effective life of the patent, whichever is longer, and will be replaced if it becomes nonviable during that period.