Abstract:
A synthetic hybrid corn plant having the designation LP41, produced by crossing two proprietary Pfister Hybrid Corn Company maize synthetics, LP41A-Reid and LP41B-Lancaster. LP41 has the unique property of imparting high oil and high protein levels in the grain of certain normal and male sterile hybrids when used as a pollinator. LP41 is characterized by excellent cold tolerant seedling vigor for rapid emergence in cold soils, and excellent early-season adaptability to nick with early maize hybrids that condition fast dry-down and superior grain quality in the recipient female grain parent. This invention thus relates to the synthetic hybrid plants and seeds of LP41, i.e., the synthetic hybrid produced by crossing the two aforementioned parental synthetics and the seed thereof, including advanced generation seed, variants, mutants, and modifications of LP41.

Description:
FIELD OF THE INVENTION 
     This invention is in the field of plant breeding. Specifically, this invention relates to a novel synthetic corn hybrid having the designation LP41 and useful in the proprietary TopCross™ grain production system described in pending U.S. patent application Ser. No. 07/615,839 by Bergquist et al. 
     BACKGROUND OF THE INVENTION 
     Uses Of Corn 
     Corn (Zea mays L.) is an important crop used as a human food source, animal feed, and as a raw material in industry. The food uses of corn, in addition to the human consumption of corn kernels, include products of both the dry milling and wet milling industries. The principal products of dry milling include grits, meal and flour. The principal products of wet milling include starch, syrups, and dextrose. A by product of both dry and wet milling is corn oil, which is recovered from corn germ. As animal feed, corn is used primarily as a feedstock for beef cattle, dairy cattle, swine, poultry, and fish. 
     Industrial uses of corn mainly consist of the use of corn starch produced by wet milling and corn flour produced by dry milling and the whole kernel fermentation for production of food-grade and industrial use ethanol. The industrial applications of corn starch and flour are based on their functional properties, such as viscosity, film formation ability, adhesiveness, absorbent properties and ability to suspend particles. Corn starch and flour are used in the paper and textile industries, and as components in adhesives, building materials, foundry binders, laundry starches, sanitary diapers, seed treatments, explosives, and oil-well muds. Plant parts other than the corn kernels are also used in industry. For example, stalks and husks can be made into paper and wallboard, and corn cobs can be used for fuel and to make charcoal. 
     Principles of conventional plant breeding 
     Virtually all of the commercial corn produced in the United States is produced from hybrid seed. The production of hybrid seed first requires the development of elite corn inbred lines that possess good combining ability to produce agronomically superior hybrids. The majority of hybrid seed produced in the United States is of the single cross type, wherein two inbred lines are intermated, or crossed, to produce what is termed an F 1  single cross hybrid. The resulting kernels from this intermating are then sold as seed to commercial growers who plant the seed and harvest the second generation, or F 2  grain, for use on farm or for commercial sale. 
     The production of a conventional single cross hybrid seed involves controlling the direction of pollination from one inbred to the other to assure the production of predominantly hybrid (cross pollinated) seed. Typically directed pollination is accomplished by interplanting separate rows of female corn plants with male corn plants. The female corn plants that are male sterile may be produced by genetic mechanisms which render the corn tassel nonfunctional or by detassling the plants in the field. 
     The development of corn hybrids requires the development of homozygous inbred lines or uniform synthetic populations of unique heterotic background, the crossing of these lines or synthetic populations, and evaluation of test crosses. Pedigree breeding and recurrent selection breeding programs are used to develop inbred lines and synthetic populations from breeding populations. Breeding various broad-based sources into breeding pools from which new inbred lines or synthetic populations are developed by inbreeding or random mating and selection of desired phenotypes. The new inbreds and/or synthetic lines are crossed with other inbred lines and/or synthetic populations and the hybrids from these crosses are evaluated to determine which have commercial value and agronomic usefulness. 
     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 complements the other. If the two original genotypes do not provide all of the desired characteristics, other sources can be included during the breeding. In the pedigree breeding method, superior plants are selfed or random mated and the resulting seed selected in successive generations. Pedigree records of ancestry are carefully maintained for each family and ear row selection through succeeding generations. In the succeeding generations, the heterozygous condition of the corn germplasm gives way to homozygous true breeding lines as a result of inbreeding and selection. Typically in the pedigree method of breeding, five or more generations of inbreeding and selection is practiced: F 1  to F 2  ; F 2  to F 3  ; F 3  to F 4  ; F 4  to F 5 , etc. 
     Backcrossing can be used to improve an inbred line by transferring a specific desirable trait from one inbred or source to another inbred that lacks that trait. This can be accomplished, for example, by first crossing a superior inbred (recurrent parent) to a donor inbred (nonrecurrent parent). The donor inbred carries (donates) the appropriate gene(s) for the desired trait to the next generation. After five or more backcross generations with selection for the desired trait, the inbred 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 can be selfed to produce a pure breeding progeny for the gene(s) being transferred. 
     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 or synthetics that give the best hybrid have been identified, the hybrid seed can be reproduced indefinitely as long as the homogeneity of the inbred or synthetic parents is maintained. 
     A synthetic hybrid consists of an array of similar genotypes that were identified from intercross tests and bulked into a random mating population having a desired phenotype. The intercrosses between two different heterotic groups results in the continuous production of a specific synthetic hybrid of desired phenotype. 
     As previously noted, a single cross hybrid is produced when two unrelated inbred or synthetic lines are crossed to produce the F 1  progeny. A three-way cross hybrid is produced from three inbred lines (or synthetics) where two of the inbred lines (or synthetics) are crossed (A×B) and then the resulting F 1  hybrid is crossed with the third inbred (or synthetics) (A×B)XC. A double cross hybrid is produced from four inbred lines (or synthetics) by crossing pairs (A×B) and (C×D) and then crossing the two F 1  hybrids (A×B)×(C×D). 
     Much of the hybrid vigor exhibited by F 1  hybrids is lost in the next generation (F 2 ). Consequently, seed (grain) from hybrid varieties is not used for planting stock. 
     The objective of typical plant breeding is to combine in a single variety/hybrid the desirable traits of the parental lines. For field crops such as corn, these desirable traits may include resistance to diseases, insects, herbicide tolerance, and tolerance to heat and drought, reducing time to crop maturity, and improved agronomic quality. With mechanical harvesting of many crops, uniformity of plant characteristics such as germination time and stand establishment, growth rate, and fruit/seed size are also desirable. 
     The problem with conventional breeding techniques is that there are several grain quality traits, such as high oil content, that cannot readily be combined in a high-yielding single cross hybrid. The present invention, when used as a pollinator, imparts desirable grain quality characteristics, such as high oil content, to the resulting F 1  grain without significant loss of yield. This heretofore was not possible because these desirable grain quality characteristics in hybrids usually have been associated with low yield and poor agronomic characteristics. 
     Synthetic varieties 
     Corn has male flowers, located on the tassel, and female flowers, located on the ear, of the same plant. Because of this monoecy, corn plants can be bred by both self-pollination and cross-pollination techniques. Corn is self-pollinated if pollen from one flower is transferred to the same or another flower on the same plant. Corn is cross-pollinated if the pollen comes from a flower on a different plant. 
     Plants that have been self-pollinated and selected for uniform type over many generations become homozygous at almost all gene loci and produce a uniform population of true breeding progeny. Cross pollination between two homozygous lines produces a uniform population of hybrid plants that nevertheless may be heterozygous for many gene loci. A cross between two plants that are each heterozygous for a number of gene loci will produce a population of hybrid plants that differ genetically and will not be uniform. 
     Natural pollination occurs when wind blows pollen from tassels to silks that protrude from tops of the incipient ears on plants of the same genotype and different genotype, resulting in both self- and cross- pollination. When a population of genotypes are combined from all possible intercrosses among a number of selected genotypes and are allowed to open pollinate, the result is called a synthetic variety. A synthetic variety is made up of genotypes which previously have been tested for their ability to produce a superior progeny when crossed in all combinations. 
     Corn plants may be maintained as an outcrossing synthetic population that is much less homogeneous than a self-pollinated group. Every plant in such a group is certain to be heterozygous at many or most loci, and this heterozygosity must either be maintained during a breeding program or restored at the end of the program, if productivity is to be satisfactory. The main requirement in maintaining a synthetic line is that a sufficient number of plants of heterozygous background be maintained to recover the gene frequencies that are desired for the synthetic population so as to prevent genetic drift toward undesired gene frequencies. 
     The desirability of high oil content grain 
     The concentration of oil in most varieties of corn ranges from less than 3.0 percent to 4.5 percent at 0% moisture. Embryos of ordinary corn can contain 30 percent oil, while embryos of high oil corn strains can contain as much as 50 percent oil and are much larger in size than ordinary corn embryos. 
     There are several reasons for wanting to develop a method for growing corn that is high in oil content. First, corn oil is a premium oil and regularly more valuable than starch, the other major component of corn kernels. Second, high oil corn possesses a higher available energy content than ordinary corn, and thus is a more valuable feed for poultry and livestock. In animal feeding trials it has been found that less high oil corn is required per unit of gain than is required with ordinary corn. In addition, high oil corn requires substantially less soybean meal to balance a typical animal diet, and may be used to replace oil containing additives in animal feed. 
     Additional impetus was given to breeding corn for high oil by the development of wide-line nuclear magnetic resonance spectroscopy (NMR) and near-infrared spectroscopy (NIR) as analytical tools for the nondestructive analysis of bulk or single kernel samples that can be carried out in as little as two seconds. The development of such tools made it much easier and much quicker to determine the oil content of grain, thereby encouraging experimentation in the area of breeding for high oil. 
     Thus there exists at present a growing market for corn having high oil, increased protein and other special end-use properties which is not met by corn of standard composition. The diverse types of corn available to plant breeders provides a potential for modification of quality and quantity of grain protein, starch, and oil. Corn now can be developed to more precisely meet the specific nutritional requirements of animals or to meet particular industrial needs. 
     The TopCross™ grain production system 
     Unfortunately, high oil is a property that cannot readily be achieved in a high yielding single-cross hybrid. This is because oil content, while being a moderately heritable trait, is influenced by a series of oil genes that have additive effects on oil content and occur at a complex of loci in at least eight linkage groups that influence the amount of oil in the grain progeny. Obtaining a hybrid having all or most of these oil genes can take many years of breeding. Further increasing the difficulty of breeding for high oil content is the fact that the grain yield of higher oil hybrids is generally inferior when compared to elite dent corn hybrids. 
     A method of producing a high yield of corn having high oil content without requiring years of breeding is described in Bergquist et al. U.S. patent application Ser. No. 07/615,839. The primary aspect of this method, known as the TopCross™ grain production system, is the interplanting of a pollinator corn plant possessing the characteristics for significantly increasing oil and protein levels in the resulting grain with a male sterile hybrid corn plant. The resulting grain possesses an oil content much higher than would be expected for self- or cross- pollination of the fertile version of the hybrid corn plant. 
     In practice, the seed of the pollinator with improved grain quality traits is blended in small amounts with seed of an elite male sterile grain parent hybrid, but with sufficient pollinator seed to permit abundant pollen production for fertilization of the male sterile grain parent hybrid. The relatively low ratio of pollinator seed to male sterile grain parent seed (less than one pollinator plant to every three grain parent plants) takes advantage of the higher grain yield potential of the elite grain parent hybrid while assuring a sufficient population of pollinator plants to pollinate the male sterile grain parent plants. 
     Need for superior pollinators 
     Critical to the success of the TopCross™ grain production system is the use of a pollinator capable of enhancing the grain quality traits of the F 1  offspring. To obtain such pollinators, the corn breeder must select and develop corn plants that have the traits that result in superior inbred and synthetic parental lines. 
     The pollinator for the TopCross™ grain production system need not be genetically homozygous (inbred) or even uniform in appearance, and need not be selected for genetic combining ability with female plants. However, the pollinator should have uniform desirable grain quality characteristics, such as high oil, that will influence the grain quality characteristics of the F 1  offspring, and the ability to pollinate the female plants. A hybrid obtained by crossing two synthetic populations of different heterotic backgrounds results in a synthetic hybrid with predictable heterozygosity and genetic variability among plants that is particularly useful as a male pollinator in blends with male sterile hybrid grain parents in the TopCross™ grain production system. Some genetic variability is desirable because it extends the flowering period of the pollinator. LP41 was developed to achieve these characteristics. 
     Advantages of synthetic hybrids 
     The use of synthetic hybrids (such as LP41) as TopCross™ grain production system pollinators affords a number of advantages over the use of hybrids produced from single crosses. For instance, synthetic hybrids can be developed more rapidly than commercial hybrids. Specifically, the use of a synthetic population can more rapidly establish stability of dominant oil genes, thereby by-passing the many generations of inbreeding that is required to produce inbreds for making single cross hybrids. 
     Second, synthetic hybrids often have excellent vigor comparable to that of commercial hybrids. Inbreds, by contrast, typically lose vigor with each successive generation of inbreeding. This is an important advantage of synthetics because pollinator vigor is critical for ample pollen shed at the time of silking in the TopCross™ grain production system. Synthetic hybrid LP41 expresses cold vigor in seedling growth stages greater than even most open pollinated synthetic populations. 
     Third, a synthetic variety, utilizing heterosis in which pollination control is a factor, is more likely to disperse pollen over a longer period of time than a single cross hybrid. The predictable greater variability of synthetic varieties as compared with single crosses permits more flexibility to meet the changing growing conditions typical of field production. In addition, because of the longer flowering period, fewer synthetic pollinators need be developed to be used in blends with many different grain parents. 
     Fourth, the synthetic hybrid pollinator is more easily produced during periods of heat and drought stress on dryland production than a single-cross hybrid using less vigorous inbred seed stocks. 
     SUMMARY 
     According to the invention, there is provided a novel synthetic corn hybrid, designated LP41, that when used to pollinate an elite male sterile hybrid grain parent, produces commercial grain exhibiting improved quality grain traits, including high oil and protein. The invention thus relates to the seeds, plants and plant parts of LP41; to plants regenerated from tissue culture of the plants or plant parts of LP41; and to a method of producing LP41 by crossing synthetic LP41A-Reid and LP41B-Lancaster synthetics. 
     DEFINITIONS 
     In the description and examples that follow, a number of terms are used. 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: 
     Adaptation. The process by which individuals (or parts of individuals) or populations change in form or function to better survive under given environmental conditions. Also the result of this process. 
     Anthesis. The period or act of flowering. 
     Backcross. The cross of a hybrid to either one of its parents. The offspring of such a cross is referred to as the backcross generation. 
     Backcross Method of Breeding. A system of breeding carried out by several generations of backcrossing to one of the parents of a hybrid and subsequent selection. The characteristics of the recurrent parent are retained for the most part, and characteristics from the nonrecurrent parent are added. 
     Barren Plants. Plants that lack ears, typically measured in number of plants per plot. 
     Brittle Stalks. This is a measure of the stalk breakage near the time of pollination of the hybrids, and is an indication of whether a hybrid would snap or break at the time of flowering under severe winds. 
     Bulk Method of Breeding. The growing of segregating generations of a hybrid of self-pollinating crops in a bulk, with or without mass selection, followed by individual plant selection in F 6  or later generations. 
     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. A high score indicates that the grain shells off of the cob well, and the cob does not break. 
     Cytoplasmic Inheritance. Transmission of hereditary characters through the cytoplasm as distinct from transmission by genes carried by chromosomes. Detected by differing contribution of male and female parents in reciprocal crosses. 
     Diallel Cross. The crossing in all possible combinations of a series of genotypes. 
     Donor parent. The parent from which one or a few genes are transferred to the recurrent parent in backcross breeding. 
     Ear Height. The ear height is a measure from the ground to the top developed ear node attachment and is measured in centimeters. 
     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 hybrid. 
     Embryo. The rudimentary plant in a seed. The embryo arises from the zygote. In high oil corn breeding, increases in oil content are accompanied by increases in embryo size. 
     Endosperm. The nutritive tissue formed within the embryo sac in seed plants. It commonly arises following the fertilization of the two primary endosperm nuclei of the embryo sac by the two male sperms. In a diploid organism the endosperm is triploid. 
     Expressivity. The degree of manifestation of a genetic character. 
     F 1 . The first generation of a cross. 
     F 2 . The second filial generation obtained by self-fertilization or crossing inter se of F 1  individuals. 
     F 3 . Progeny obtained by self-fertilizing F 2  individual. Subsequent generations F 4 , F 5 , etc. 
     GDD Shed. The GDD is the number of growing degree days (GDD) or heat units required for an inbred line or hybrid to reach anthesis or pollen shed from the time of planting. Growing degree days are calculated by the Barger Method, where the heat units for a 24-hour period are: ##EQU1## The highest maximum used is 86 degrees F. and the lowest minimum used is 50 degrees F. For each hybrid it takes a certain number of GDDs to reach various stages of plant development. GDDs are a way of measuring plant maturity. 
     Genotype. The fundamental genetic constitution of an organism. 
     Grain Quality. This is a 1 to 5 rating for the general quality of the shelled grain as it is harvested based on the color of the harvested grain, any mold on the grain, and any cracked grain. Low scores indicate good grain quality. 
     Grain Quality Trait. This is any attribute of grain that is of commercial value. Such traits relate to the intermediate or final use of grain and include but are limited to the quantity or quality of oil, protein, starch, pigmentation, and fiber found in corn grain. Such traits also encompass physical attributes of the grain itself, such as grain texture, size, or hardness, among others. Certain of these compositional or physical attributes of grain correlate with functional attributes as well which are of commercial importance, such as susceptibility to breakage and spoilage, among others. 
     Hybrids. (1) The progeny of a cross fertilization between parents belonging to different genotypes. (2) The first generation offspring of a cross between two individuals differing in one or more genes. (3) A hybrid is the result of a cross between two or more components. 
     Hybrid Vigor. The phenomenon in which the cross of two stocks produce hybrids that show increased vigor-heterosis compared to the parent stocks. 
     Inbred Lines. (1) A line produced by continued inbreeding. In plant breeding a nearly homozygous line usually originating by continued self-fertilization, accompanied by selection. (2) A relatively homozygous line produced by inbreeding and selection. 
     Male Sterility. A condition in which pollen is absent or non-functional in flowering plants. 
     MN RM. This represents the Minnesota Relative Maturity Rating (MN RM) for the hybrid and is based on the harvest moisture of the grain relative to a standard set of checks of previously determined MN RM rating. Regression analysis is used to compute this rating. 
     Moisture. The moisture is the actual percentage moisture of the grain at harvest. 
     Multiple Genes. Two or more independent pairs of genes which produce complementary or cumulative effects upon a single character of the phenotype. 
     Pedigree. A record of the ancestry of an individual, family, or strain. 
     Pedigree Breeding. A system of breeding in which individual plants are selected in the segregating generations from a cross on the basis of their desirability and on the basis of a pedigree record. 
     Penetrance. (1) The proportion of organisms heterozygous for a particular dominant gene or homozygous for a recessive which shows the phenotype under a set of specified environmental conditions; (2) complete penetrance is the situation in which a dominant gene always produces a phenotypic effect or a recessive gene in the homozygous state always produces a detectable effect; (3) the frequency with which a gene produces a recognizable effect in individuals which carry it. 
     Percent Yield. The percent yield is the yield obtained for the hybrid in terms of percent of the mean for the experiments in which it was grown. 
     Phenotype. (1) Physical or external appearance of an organism as contrasted with its genetic constitution (=genotype); (2) a group of organisms with similar physical or external makeup; (3) the observed character of an individual without reference to its genetic nature. 
     Plant Height. This is a measure of the height of the hybrid from the ground to the tip of the tassel and is measured in centimeters. The data is given in percentage of mean of the experiments in which the hybrid was grown. 
     Pollinator. Male fertile corn plants that are used to pollinate male sterile hybrid corn plants. 
     Population. In genetics, a community of individuals which share a common gene pool. In statistics, a hypothetical and infinitely large series of potential observations among which observations actually made constitute a sample. 
     Predicted R.M. Predicted relative maturity is based on the harvest moisture of the grain. The relative maturity rating (R.M.) is based on a known set of checks and utilizes standard linear regression analyses referred to as the Minnesota Relative Maturity Rating System. 
     Quantitative Character. A character in which variation is continuous so that classification into discrete categories is not possible. Also, a character determined by a series of independent genes which are cumulative in their effect. 
     Recurrent Parent. Used in backcrosses to refer to the parent to which the first cross and successive backcrossed plants are crossed. 
     Root Lodging. The percentage of plants that root lodge; i.e., those that lean from the vertical axis at an approximately 30 degree angle or greater would be counted as root lodged. 
     Seedling Vigor. This is the visual rating (1 to 5) of the amount of vegetative growth after emergence at the seedling stage (approximately five leaves). A higher score indicates better vigor. 
     Selection Index. The selection index gives a single measure of a hybrids&#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. 
     Self-fertilization. The fusion of the female egg cell of one individual with a male sperm cell of the same individual. 
     Sibs: Progeny of the same parents derived from different gametes. Half sibs, progeny with one parent in common. 
     Single Cross. A cross between two genotypes, usually two genetically different inbred lines or synthetic lines. 
     Stalk Lodging. This is the percentage of plants that do not stalk lodge, i.e., stalk breakage, as measured by either natural lodging or pushing the stalks and determining the percentage of plants that break off below the ear. This is a relative rating of a hybrid to other hybrids for standability. 
     Stay Green. Stay green is the measure of plant health near the time of black layer formation (physiological maturity). A low score on a scale of 1 to 5 indicates better late-season plant health. 
     Synthetic Variety. A variety produced by crossing inter se a number of genotypes selected for good combining ability in all possible hybrid combinations, with subsequent maintenance of the variety by open pollination. 
     Test Cross. A cross of a double or multiple heterozygote to the corresponding multiple recessive to test for homozygosity or linkage. 
     Test Weight. This is the measure of the weight of the grain in pounds for a given volume (bushel) adjusted for percent moisture. 
     Topcross. (1) A cross of a hybrid or synthetic or inbred to a multiple heterozygote of opposite corresponding multiple loci to obtain traits observed in the pollen donor parent; (2) a cross between a selection line, clone, etc., and a common pollen parent which may be a variety, inbred line, single cross, etc. The common pollen parent is called the topcross or tester parent. (3) In corn, a topcross is commonly an inbred-variety cross, an outcross of selections, clones, lines, or inbreds, to a common pollen parent. 
     TC Blend™. A trademark of E. I. DuPont de Nemours and Company, Inc. for a physical seed mixture of pollinator seed and male sterile grain parent seed meeting specific quality criteria. 
     TopCross™ Grain. The grain which results from the planting of TC Blend™ seed and having improved nutrient composition and grain quality. TopCross™ is trademark of E I. DuPont de Nemours and Company, Inc. for grain produced by the TopCross™ grain production system. 
     TopCross™ Grain Production System. A method of commercial corn production whereby a low yielding male fertile corn pollinator is blended at 8 to 20 percent of the total seed count with an elite high yielding male sterile hybrid grain parent and allowed to pollinate the male sterile grain parent to produce TopCross™ grain having increased food and feed nutritional value, thus capitalizing on the high yield potential of the male sterile hybrid grain parent while contributing the grain quality traits from the fertile pollinator. 
     Variety. A subdivision of a species. A group of individuals within a species which are distinct in form or function from other similar arrays of individuals. 
     Yield (Bushels/Acre). The yield in bushels/acre is the actual yield of the grain at harvest adjusted to 15.5% moisture. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     LP41 is a yellow dent corn, high oil single cross synthetic hybrid having superior agronomic characteristics and the ability to impart desirable grain quality traits to a first generation grain when used as a pollinator in the TopCross™ grain production system. 
     Synthetic hybrid LP41 is produced by planting synthetic populations LP41A and LP41B, allowing one synthetic to pollinate the other, and harvesting the resulting seed. Either synthetic parental population may be used as female parent or the male parent. Preferably, synthetic LP41B should be the female of the cross and synthetic LP41A should be the male of the cross because of the larger seed size grade-out resulting from the LP41B seed parent in hybrid synthetic production. Production planting of the male and female synthetics can be made at the same time due to the fact that male pollen is shed at the same time the female silks are receptive to the pollen. 
     LP41A and LP41B were produced by conducting a series of crosses, selfings and backcrosses beginning with the crossing of LH132 with ASKC28 (for LP41A) and the crossing of LH51 and LH59 with ASKC28 (for LP41B). During the development of LP41A and LP41B, test crosses were made and the resulting grain analyzed to identify normal grain type segregants with favorable dominant oil genes. 
     When produced according to the method disclosed herein, both LP41A and LP41B breed true, that is, produce an LP41 synthetic hybrid that is both reproducible and usable as a high oil TopCross pollinator. 
     CHARACTERISTICS 
     Synthetic corn hybrid LP41 most closely resembles maize synthetics ASKC28, ASKC20 and UHO in characteristics of plant type, ear type, kernel type and usage, but LP41 is considerably earlier in maturity and expresses higher grain test weight with normal grain and dent phenotype. 
     LP41 synthetic hybrid has the following characteristics, based on data primarily collected at El Paso, Ill.: 
     
                       TABLE 1______________________________________SYNTHETIC HYBRID DESCRIPTION INFORMATION______________________________________A. Maturity:       Zone 0Synthetic Hybrid:  LP41Heat Units from Emergence to Shed:              1089.0 GDDHeat Units from Emergence to Silk:              1137.5 GDDHeat Units from 50% Silk to              1292.5 GDD25% Kernel Moisture:Heat Units from Emergence to              2430.0 GDD25% Kernel Moisture:No. Reps.:         8Heat Units* =        (Max. Temp. (&lt;86 Degrees F) +       Min. Temp. (&gt;50 Degrees F.)) / 2! - 50B. Plant Characteristics:Height (to tassel tip):              198 cmLength of Top Ear Internode;              16 cmNumber of Ears per Stalk:              1-2, slight two-ear              tendencyEar Height (to base of top ear):              70 cmNumber of Tillers: NoneCytoplasm Type:    NormalBrace Root Color:  Pale GreenNumber of Brace Root Nodes:              1Number of Brace Roots:              8C. Leaf:Color:             Pale GreenStalk Color:       Dark GreenAngle from Stalk:  53 DegreesMarginal Waves (number):              2-3, fewNumber of Leaves (mature plants):              12Sheath Pubescence: Smooth, pubescence absentLongitudinal Creases:              PresentLength (Ear node leaf):              73 cmWidth (widest point,              9 cmear node leaf):Coleoptile Sheath Color:              GreenD. Tassel:Number Lateral Branches:              13Branch Angle from central spike:              62 degreesLength (from flag leaf):              46 cmPeduncle Length (flag leaf to              9 cmbasal branches):Anther Color:      Pale green, segregating              pink anther color but was              heterozygous for pale              greenGlume Color:       GreenE. Ear (Husked Ear Data ExceptWhen Stated Otherwise):Length:            20 cmWeight (dried to 15.5%              116 gmgrain moisture):Mid-point Diameter:              4.6 cmSilk Color (at silking):              Pale greenHusk Extension (Harvest stage):              Short, 6.6 cmHusk Leaf (number):              5Husk Leaf Length:  5 cmNumber of Husks:   11Taper of Ear:      Average taperPosition at Dry Husk Stage:              UprightKernel Rows:       18; Distinct, straight,              segregating 14 to 22Husk Color (fresh):              Light greenHusk Color (dry):  BuffShank Length:      15 cm longShank (No. of internodes):              10Drying Time (unhusked ear):              AverageHusk Length:       26 cmHusk Width:        15 cmHusk Area:         390 cm2F. Kernel (dried, size from earmid-point):Length:            10 mmWidth:             7 mmThickness:         3 mmShape Grade (% rounds):              34% (±3%) based on parent              testPericarp Color:    ColorlessAleurone Color:    Homozygous; yellowCap Color:         YellowEndosperm Color:   YellowEndosperm Starch Type:              Normal starchGm Wt/100 Seeds (unsized):              19 gmTest Weight:       60 lbs./bu.Percent Oil:       13.6 percentPercent Protein:   14.8 percentPercent Starch:    57.2 percentG. Cob (dried, size from earmid-point):Diameter at mid-point:              25 mmStrength:          StrongColor:             Red, segregating for              white and red cob color              but was heterozygous for red.H. Diseases:Northern Leaf Blight:              IntermediateGoss&#39;s Bacterial Wilt:              IntermediateSouthern Corn Leaf Blight:              SusceptibleHeat Smut:         SusceptibleCommon Smut:       ResistantStewart&#39;s Bacterial Wilt:              IntermediateCorn Lethal Necrosis:              SusceptibleNorthern Leaf Spot:              IntermediateCommon Northern Rust:              IntermediateSouthern Rust:     SusceptibleEye Spot:          IntermediateGray Leaf Spot:    SusceptibleFusarium Ear Rot:  ResistantFusarium Stalk Rot:              IntermediateDiplodia Ear Rot:  SusceptibleDiplodia Stalk Rot:              IntermediateMDMV:              SusceptibleStunt:             SusceptibleStay Green:        IntermediateI. Insects:European Corn Borer:              Susceptible______________________________________ *If Max. Temp. is greater than 86 degrees Fahrenheit, then 86 is used and if Min. Temp. is less than 50, then 50 is used. Heat units accumulated daily and can not be less than 0. 
    
     LP41 is adapted over a wide area of the northern corn belt and can be used advantageously in seed blends with male sterile hybrids from approximately 96-110 relative maturity based on the Minnesota Relative Maturity Rating System for harvest moisture of the grain. LP41 cold test vigor was excellent in laboratory tests, exhibiting 95% emergence compared to 90% emergence for ASKC20, 92% emergence for UHOC3, and 83% emergence for ASKC28 (LSD=8.5%; C.V.=5.6% at 0.05 and Stand. Dev.=4.4). Kernel size-out is also very good for LP41, with approximately 66 percent of the kernels falling in the medium flat category. 
     Although LP41&#39;s primary use would be as a pollinator in the TopCross™ grain production system with blends of early maturing corn hybrid male sterile grain parents, it is also an acceptable male to be crossed to later maturing full season high oil pollinators to develop medium maturity pollinators for expanding the use of its genetics to fuller season maturity grain parents. 
     Pollen production is good with LP41. Under extreme heat and drought stress, LP41 may top fire and have some tassel blasting (necrosis of top leaves and tassel, respectively). It sheds pollen for approximately sixteen days and should be planted in 8 to 20 percent blends to ensure adequate pollen in commercial production of TopCross™ grain where it is used as a male pollinator. 
     LP41 has shown uniformity and stability within the limits of environmental influence for all traits as described in Table 2. LP41 has expressed segregation for red and white cob color because of the genetic differences of LP41A and LP41B synthetic parent populations. LP41 is a synthetic hybrid that has been maintained by hand and cross pollination in isolated fields with continued observation of high oil for uniformity of dominant high oil genetics. Although segregating for cob color, glume color and plant height in test crosses, LP41 synthetic has consistently expressed high oil across different environments. 
     LP41 is an early-medium maturity flowering synthetic hybrid, broadly adapted to the corn growing areas of the Northern United States and Southern Canada. LP41 has high oil and excellent cold soil seedling vigor that conditions low grain moisture in the grain of the male sterile hybrid grain parent. 
     BENEFITS OF LP41 AS A POLLINATOR 
     In field tests of the TopCross™ grain production system using LP41 as the pollinator and a male sterile hybrid grain parent, plants of both varieties were allowed to grow unmolested to maturity. Both varieties were allowed to continue to grow and natural cross-pollination occurred by the action of wind as is normal in most grasses, including corn (i.e., excluding wheat). Of course, only pollen from the male parent synthetic hybrid, LP41, was available for pollination of the male sterile hybrid grain parent; the tassels, or pollen bearing flowering parts, of the grain parent having been rendered sterile by genetic/cytoplasmic mechanisms. 
     The fields where high oil TopCross™ grain was produced were well isolated from other corn fields to prevent any accidental contamination with ambient pollen. Such isolation techniques may be accomplished by timed delay with other hybrid corn production fields or by using a space distance pattern of more than 70 m from normal corn, well known to those skilled in the art of the seed corn industry. 
     Both varieties comprising the corn seed blend were allowed to continue to grow and be harvested. The ears harvested from the male sterile grain parent expressed the higher grain yield potential of the elite male sterile grain parent and the high oil, protein and grain density qualities of the pollen parent. The grain from the male parent variety ears can also be harvested along with the grain of male sterile grain parent for high oil corn use. 
     Because the same oil source (i.e. ASKC28) was used in the development of the LP41-A-Reid and LP41-B-Lancaster populations, only modest heterotic effects for yield were expressed in LP41. The low grain yields expected from synthetic hybrid LP41 pollinator dictated the need for a low percent of pollinator in the pollinator-grain parent seed blend so as to recover the grain quality traits of the pollinator, but a high enough. percent to produce sufficient pollen to maintain the higher yield potential of the elite male sterile grain parent hybrid. 
     The field tests indicated that LP41 induces superior grain quality characteristics to TopCross™ grain of the male sterile hybrid grain parent as a result of being pollinated by LP41. That is to say, the grain quality traits and high oil characteristics of LP41 were transferred to the grain of the male sterile grain parent. 
     EXAMPLES 
     In the examples that follow, the characteristics of TopCross™ grain produced using LP41 as a pollinator are provided. 
     First year (1993) strip test trials were conducted in El Paso, Ill., comparing the characteristics of grain from various Pfister hybrids rendered male sterile and pollinated by LP41 with the characteristics of grain produced from grow outs of the same Pfister hybrids in their fertile state. The hybrids used were Pfister hybrids 2375, 3000, X577, X570, 3333, 3339, X465 and Kernoil®-10. These results are presented in Table 2. 
     
                                           TABLE 2__________________________________________________________________________1993 LP41 Strip Test Results - El Paso, Illinois         Grain Yield-Bu/A.                     Moisture Percent                                 Oil PercentHybrid Grain       %           %           %Parent (GP) and    of Hybrid   of Hybrid   of HybridLocation      TopCross              GP Self                     TopCross                          GP Self                                 TopCross                                      GP Self__________________________________________________________________________Pfister Hybrid 2375-Sdms         119.5              107                 111.4                     18.7 97 19.2                                 6.74 141                                         4.77Pfister Hybrid 3000-Sdms         140.4              118                 119.3                     19.6 98 20.1                                 6.58 150                                         4.38Pfister Hybrid X577-Sdms         134.0              115                 117.0                     19.0 93 20.4                                 6.81 142                                         4.81Pfister Hybrid X570-Sdms         126.6              112                 112.9                     22.4 102                             22.0                                 6.11 139                                         4.38Pfister Hybrid 3333-Sdms         123.6              103                 119.6                     22.0 99 22.3                                 5.81 129                                         4.49Pfister Hybrid 3339-Sdms         115.3              94 122.4                     22.8 106                             21.6                                 6.01 152                                         3.95Pfister Hybrid X465-Sdms         103.6              87 118.5                     23.6 103                             23.0                                 5.57 127                                         4.38Pfister Hybrid Kernoil 10-Cms         90.6 116                 78.3                     21.1 77 27.5                                 7.75 121                                         6.39Overall Mean  118.7              106                 112.9                     21.1 96 22.0                                 6.42 137                                         4.69__________________________________________________________________________ 
    
     Traits obtained from the strip test data, in addition to those defined previously, included the following: 
     &#34;Grain yield&#34;, expressed in bushels per acre for both the grain produced by the pollination of the male sterile hybrid by LP41 and for the fertile hybrid. Grain yield from the male sterile/LP41 seed blend is also expressed as a percent of the yield from the fertile grain parent yield (% of GP). 
     &#34;Moisture Percent&#34; (for grain produced from the seed blend and from the fertile grain parent), expressed as a percentage of total kernel weight. Relative grain moisture was determined by distillation on a Brown-Duvel moisture tester manufactured by the Seed Trade Reporting Bureau, Chicago, Illinois. Electronic moisture testers were calibrated against the moisture determinations of the Brown-Duvel moisture tester in field harvest tests. 
     &#34;Oil Percent&#34;, the content of oil in the grain at harvest, expressed as a percent of total kernel weight. Oil percent was determined by NIR on a dry matter basis (0% moisture). 
     Second year (1994) strip test trials were conducted in El Paso, comparing the characteristics of grain from various Pfister hybrids rendered male sterile and pollinated by LP41 with the characteristics of grain produced from grow outs of the same Pfister hybrids in their fertile state. The hybrids used were Pfister hybrids X529, X577, 2020, 2320, 2375, and 3034. Additional trials were conducted in Geneseo, Ill.; Waterloo and Humbolt, Iowa; and Evansville, Wis. These results are presented in Table 3. 
     
                                           TABLE 3__________________________________________________________________________1994 LP41 Strip Test Results - Five Locations         Grain Yield-Bu/A.                     Moisture Percent                                 Oil PercentHybrid Grain       %           %           %Parent (GP) and    of Hybrid   of Hybrid   of HybridLocation      TopCross              GP Self                     TopCross                          GP Self                                 TopCross                                      GP Self__________________________________________________________________________Pfister Hybrid X529-Sdms (1)         175.1              92 190.7                     18.9 109                             17.4                                 7.15 174                                         4.11Pfister Hybrid X577-Sdms (2)         167.9              89 188.4                     22.0 103                             21.4                                 7.80 169                                         4.60Pfister Hybrid 2020-Sdms (2)         182.1              97 188.1                     18.5 97 19.3                                 7.71 177                                         4.40Pfister Hybrid 2320-Sdms (1)         157.5              92 171.0                     16.4 97 16.9                                 7.50 179                                         4.20Pfister Hybrid 2375-Sdms (1)         138.0              77 178.5                     18.8 106                             17.8                                 7.28 170                                         4.29Pfister Hybrid 3034-Sdms (1)         157.1              82 191.6                     17.6 99 17.8                                 7.53 187                                         4.03Overall Mean  170.0              91 187.0                     19.5 100                             19.5                                 7.64 174                                         4.40__________________________________________________________________________ (1) Tests conducted at El Paso, Illinois. (2) Tests conducted at Geneso and El Paso, Illinois; Waterloo and Humbolt Iowa; and Evansville, Wisconsin. 
    
     Third year (1995) strip test trials were conducted in El Paso, comparing the characteristics of grain from various Pfister hybrids rendered male sterile and pollinated by LP41 with the characteristics of grain produced from grow outs of the same Pfister hybrids in their fertile state. The hybrids used were Pfister hybrids X571, 2020, X641, 1571, 2320, X642 and X591. Additional trials were conducted at corn research stations in Livingston, Janesville and Mequon, Wis.; Williamsburg, Linn Grove, New Hampton, Manilla, Cedar Falls, Shell Rock and Humbolt, Iowa; Dennison and Cannon Falls, Minn.; Geneseo and Atkinson, Ill. and David City, Nebr. These results are presented in Table 4. 
     In third year strip tests, protein content was determined and is expressed as the percentage of protein in the grain on a dry matter basis as determined by NIR. 
     
                                           TABLE 4__________________________________________________________________________1995 LP41 Strip Test Results - Sixteen Locations       Grain Yield-Bu/A.                    Moisture Percent                                 Oil Percent  Protein PercentHybrid Grain     %            %            %            %Parent (GP) and  of  Hybrid   of  Hybrid   of  Hybrid   of HybridLocation    TopCross            GP  Self                    TopCross                         GP  Self                                 TopCross                                      GP  Self                                              TopCross                                                   GP Self__________________________________________________________________________Pfister Hybrid X571-Sdms       128.5            97  132.3                    17.0 101 16.8                                 6.91 153 4.51                                              8.7   98                                                      8.9Six locationsPfister Hybrid 2020-Sdms       131.9            93  142.5                    18.0 105 17.1                                 7.05 158 4.47                                              8.8  101                                                      8.7Ten locationsPfister Hybrid X641-Sdms       127.4            93  136.7                    17.0 104 16.3                                 6.81 151 4.52                                              10.0 112                                                      8.9Nine locationsPfister Hybrid 1571-Sdms       136.7            95  143.9                    17.7 102 17.3                                 7.13 166 4.30                                              9.2  107                                                      8.6Thirteen locationsPfister Hybrid 2320-Sdms       134.6            90  149.2                    17.1 103 16.6                                 6.69 150 4.47                                              9.5  113                                                      8.4Seven locationsPfister Hybrid X642-Sdms       136.2            92  148.1                    19.1 104 18.3                                 6.61 157 4.22                                              9.4  109                                                      8.6Ten locationsPfister Hybrid X591-Sdms       136.9            90  152.1                    18.1 105 17.2                                 6.72 151 4.46                                              8.6  109                                                      7.9Nine locationsOverall Mean       133.2            92  143.5                    17.3 101 17.1                                 6.84 155 4.42                                              9.2  107                                                      8.8__________________________________________________________________________ 
    
     Yield Comparison 
     In first year trials, blends of 8-9 percent pollinator seed and 91-92 percent male sterile hybrid seed were planted and grown to maturity. Grain from both the male sterile hybrid plants and the pollinator plants were harvested. The yield of grain produced by the pollination of the male sterile hybrid by LP41 was actually higher than the yield of grain from the fertile grain parent alone in six of the eight comparisons. For example, the yield achieved from a blend of LP41 and Sdms-cytoplasmic male sterile grain parent hybrid Pfister 2375-Sdms (119.5 Bu/A) was slightly more than the yield obtained from a grow out of fertile Pfister Hybrid 2375 (111.4 Bu/A). 
     In second year trials (1994), grain yield from blends of 8-9 percent pollinator and 91-92 percent male sterile grain parent showed little loss compared to grain yield from the fertile grain parent alone. For example, the mean yield achieved in five different locations from a blend of 8-9 percent LP41 and 91-92 percent Pfister Hybrid X577-Sdms was 89% of the yield obtained from planting fertile Pfister X577 alone. 
     In third year trials (1995), grain yield from blends of 8-9 percent pollinator and 91-92 percent male sterile grain parent showed little loss compared to grain yield from the fertile grain parent alone. For example, the mean yield achieved in ten different locations from a blend of 8-9 percent LP41 and 91-92 percent Pfister Hybrid X642-Sdms was 92% of the yield obtained from planting fertile Pfister X642 alone. 
     Oil Content Of TopCross™ Grain 
     Comparisons of the oil content of TopCross™ grain were made against the oil content of grain from fertile hybrids. The oil contents of grain produced in first year strip tests of Pfister male sterile hybrids 2375-Sdms, 3000-Sdms, X577-Sdms, X570-Sdms, 3333-Sdms, 3339-Sdms, X465-Sdms and Kernoil-10-Sdms pollinated by LP41 are presented in Table 2. 
     Comparisons of these oil contents to the oil contents of the grain from the fertile checks of these hybrids in tests made at El Paso, Illinois, revealed about a 2% absolute increase in oil (6.7% compared to 4.8% for Pfister Hybrid 2375, 6.6% compared to 4.4% for Pfister hybrid 3000, 6.8% to 4.8% for Pfister hybrid X577, 6.1% compared to 4.4% for Pfister hybrid X570, 5.8% compared to 4.5% for Pfister hybrid 3333, 6.0% compared to 4.0% for Pfister hybrid 3339, 5.6% compared to 4.4% for Pfister hybrid X465 and 7.8% compared to 6.4% for Pfister hybrid Kernoil®-10). 
     In second year (1994) comparisons (Table 3), the mean oil content of grain produced by male sterile Pfister Hybrids X529-Sdms, X577-Sdms, 2020-Sdms, 2320-Sdms, 2375-Sdms, and 3034-Sdms pollinated by LP41 was 174 percent higher (7.64 percent compared to 4.40 percent) than the mean oil content of grain produced from the self pollination of the fertile hybrid alone. 
     In third year (1995) comparisons (Table 4), the mean oil content of grain produced by male sterile Pfister Hybrids X642-Sdms pollinated by LP41 at ten locations was 155 percent higher (6.84 percent compared to 4.42 percent) than the mean oil content of grain produced from the self pollination of the fertile hybrid alone. 
     Moisture Of TopCross™ Grain 
     Conventional high oil hybrids traditionally express higher grain moisture at harvest and are slower to dry down than lower-oil dent hybrids of the same maturity. To test this concept of higher moisture associated with higher oil content of grain, comparisons were made of moisture at harvest of grain resulting from the pollination by LP41 of male sterile Pfister hybrids and grain resulting from the self pollination of the comparable fertile Pfister hybrids. 
     In first year trials (Table 2), grain moisture at harvest from the sterile grain parent hybrids pollinated by LP41 was higher than the grain moisture from the fertile grain parent hybrids alone in only three of eight comparisons. Since higher oil content resulted in higher moisture content in only three of eight comparisons, the first year data did not support the conventional theory regarding the relationship between oil content and grain moisture. 
     In second year trials (Table 3), grain moisture at harvest from the sterile grain parent hybrids pollinated by LP41 was higher than the grain moisture from the fertile grain parent hybrids alone in three of six comparisons. The mean grain moisture was the same at 19.5 percent moisture. Again, the data did not support the theory that higher moisture is associated with higher oil content. 
     In third year trials (Table 4), grain moisture comparisons of population means of seven hybrids pollinated by LP41 were made against fertile hybrids and these results revealed slight increases in grain moisture in the TopCrossm high oil grain. Thus, the third year trial results tend to support the theory that higher moisture is associated with higher oil. 
     Protein Content 
     In third year (1995) strip tests in seventeen locations, protein content of the TopCross™ grain (i.e., the grain resulting from the pollination of the male sterile hybrid by LP41) was compared to the protein content of grain produced from open pollinated fertile hybrid checks. Analysis of population means indicated that LP41 significantly increased protein in the TopCross™ grain compared to the grain from the fertile grain parent check. For example, mean protein level from grain produced by the pollination of Pfister Hybrid X642 by LP41 was 109 percent higher (9.4 percent compared to 8.6 percent) than the protein level in grain produced by the self pollination of fertile X642. Mean protein level from grain produced by the pollination of Pfister Hybrid 1571 by LP41 was 107 percent higher (9.2 percent compared to 8.6 percent) than the protein level in grain produced by the self pollination of fertile 1571. 
     Tassel-Silk Synchronization 
     The success of the TopCross™ grain production system is primarily based on the synchronization of pollen shed from the pollinator with the extrusion of silks from the male sterile grain parent hybrid, which is termed nicking. 
     Comparisons of the mid-tassel shedding date of LP41 (1218.5 GDD) with the mid-silking date of sterile Pfister Hybrids 2375-Sdms, 3000-Sdms, X577-Sdms, X570-Sdms, 3333-Sdms, 3339-Sdms, X465-Sdms and Kernoil®-10-Sdms revealed that the LP41 mid-tassel date was similar to the flowering dates of Pfister Hybrids 2375, X577 and 3333; slightly later (70 GDD) than the flowering date of sterile Pfister Hybrid 3000; slightly earlier than sterile Pfister Hybrids X570-Sdms, 3339-Sdms and Kernoil-10-Sdms; and 81 GDD (approximately three days) earlier than Pfister Hybrid X465. 
     DEPOSIT INFORMATION 
     Applicant has made available to the public without restriction a deposit of at least 2500 seeds of synthetic hybrid LP41 with the American Type Culture Collection (ATCC), Rockville, Md. 20852, ATCC Deposit No. 97484. The seeds deposited with the ATCC are taken from the same deposit maintained by Pfister Hybrid Corn Company, Box 187, 187 North Fayette Street, El Paso, Illinois 61738, since prior to the filing date of this application. The deposit will be maintained in the ATCC depository, which is a public depository, for a period of 30 years, or 5 years after the most recent request, or for the effective life of the patent, whichever is longer, and will be replaced if it becomes nonviable during that period. 
     Although the foregoing invention has been described in some detail by way of illustration and examples for purposes of clarity and understanding, it will be obvious that certain modifications and alternative embodiments of the invention are contemplated which do not depart from the spirit and scope of the invention as defined by the foregoing teachings and appended claims.