主题：【合作】玉米种子 PH4CV专利翻译合作 -- 急风劲草

具有附加值的转基因(Transgenes that Confer or Contribute to a Value-Added Trait)

Transgenes that Confer or Contribute to a Value-Added Trait, Such as:

(A) Modified fatty acid metabolism, for example, by transforming a plant with an antisense gene of steary-ACP desaturase to increase stearic acid content of the plant. See Knultzon et al., Proc. Nati. Acad. Sci. USA 89: 2624 (1992).

(B) Decreased phytate content

o (1) Introduction of a phytase-encoding gene would enhance breakdown of phytate, adding more free phosphate to the transformed plant. For example, see Van Hartingsveldt et al., Gene 127: 87 (1993), for a disclosure of the nucleotide sequence of an Aspergillus niger phytase gene.

o (2) A gene could be introduced that reduces phytate content. In maize, this, for example, could be accomplished, by cloning and then re-introducing DNA associated with the single allele which is responsible for maize mutants characterized by low levels of phytic acid. See Raboy et al., Maydica 35: 383 (1990).

(C) Modified carbohydrate composition effected, for example, by transforming plants with a gene coding for an enzyme that alters the branching pattern of starch. See Shiroza et al., J. Bacteriol. 170: 810 (1988) (nucleotide sequence of Streptococcus mutans fructosyltransferase gene), Steinmetz et al., Mol. Gen. Genet. 200: 220 (1985) (nucleotide sequence of Bacillus subtilis levansucrase gene), Pen et al., Bio/Technology 10: 292 (1992) (production of transgenic plants that express Bacillus licheniformis α-amylase), Elliot et al., Plant Molec. Biol. 21: 515 (1993) (nucleotide sequences of tomato invertase genes), Sφgaard et al., J. Biol. Chem. 268: 22480 (1993) (site-directed mutagenesis of barley α-amylase gene), and Fisher et al., Plant Physiol. 102: 1045 (1993) (maize endosperm starch branching enzyme II).

(D) Elevated oleic acid via FAD-2 gene modification and/or decreased linolenic acid via FAD-3 gene modification (see U.S. Pat. Nos. 6,063,947; 6,323,392; and WO 93/11245).

耐除草药剂的转基因(Transgenes that Confer Resistance to a Herbicide)

Transgenes that Confer Resistance to a Herbicide, for Example:

(A)A herbicide that inhibits the growing point or meristem, such as an imidazolinone or a sulfonylurea. Exemplary genes in this category code for mutant ALS and AHAS enzyme as described, for example, by Lee et al., EMBO J. 7: 1241 (1988), and Miki et al., Theor. Appl. Genet. 80: 449 (1990), respectively. See also, U.S. Pat. Nos. 5,605,011; 5,013,659; 5,141,870; 5,767,361; 5,731,180; 5,304,732; 4,761,373; 5,331,107; 5,928,937; and 5,378,824; and international publication WO 96/33270, which are incorporated herein by reference in their entireties for all purposes.

(B) Glyphosate (resistance imparted by mutant 5-enolpyruvl-3-phosphikimate synthase (EPSP), and aroA genes, respectively) and other phosphono compounds such as glufosinate (phosphinothricin acetyl transferase (PAT) and Streptomyces hygroscopicus phosphinothricin acetyl transferase (bar) genes), and pyridinoxy or phenoxy proprionic acids and cycloshexones (ACCase inhibitor-encoding genes). See, for example, U.S. Pat. No. 4,940,835 to Shah et al., which discloses the nucleotide sequence of a form of EPSPS, which can confer glyphosate resistance. U.S. Pat. No. 5,627,061 to Barry et al. also describes genes encoding EPSPS enzymes. See also U.S. Pat. Nos. 6,248,876 B1; 6,040,497; 5,804,425; 5,633,435; 5,145,783; 4,971,908; 5,312,910; 5,188,642; 4,940,835; 5,866,775; 6,225,114 B1; 6,130,366; 5,310,667; 4,535,060; 4,769,061; 5,633,448; 5,510,471; Re. 36,449; RE 37,287 E; and U.S. Pat. No. 5,491,288; and international publications WO 97/04103; WO 97/04114; WO 00/66746; WO 01/66704; WO 00/66747 and WO 00/66748, which are incorporated herein by reference in their entirety. Glyphosate resistance is also imparted to plants that express a gene that encodes a glyphosate oxidoreductase enzyme as described more fully in U.S. Pat. Nos. 5,776,760 and 5,463,175, which are incorporated herein by reference in their entirety. In addition glyphosate resistance can be imparted to plants by the over expression of genes encoding glyphosate N-acetyltransferase. See, for example, U.S. Application Ser. Nos. 60/244,385; 60/377,175 and 60/377,719.

A DNA molecule encoding a mutant aroA gene can be obtained under ATCC accession No. 39256, and the nucleotide sequence of the mutant gene is disclosed in U.S. Pat. No. 4,769,061 to Comai. European patent application No. 0 333 033 to Kumada et al. and U.S. Pat. No. 4,975,374 to Goodman et al. disclose nucleotide sequences of glutamine synthetase genes which confer resistance to herbicides such as L-phosphinothricin. The nucleotide sequence of a phosphinothricin-acetyl-transferase gene is provided in European patent No. 0 242 246 and 0 242 236 to Leemans et al. De Greef et al., Bio/Technology 7: 61 (1989), describe the production of transgenic plants that express chimeric bar genes coding for phosphinothricin acetyl transferase activity. See also, U.S. Pat. Nos. 5,969,213; 5,489,520; 5,550,318; 5,874,265; 5,919,675; 5,561,236; 5,648,477; 5,646,024; 6,177,616 B1; and 5,879,903, which are incorporated herein by reference in their entirety. Exemplary of genes conferring resistance to phenoxy proprionic acids and cycloshexones, such as sethoxydim and haloxyfop, are the Acc1-S1, Acc1-S2 and Acc1-S3 genes described by Marshall et al., Theor. Appl. Genet. 83: 435 (1992).

(C) A herbicide that inhibits photosynthesis, such as a triazine (psbA and gs+genes) and a benzonitrile (nitrilase gene). Przibilla et al., Plant Cell 3: 169 (1991), describe the transformation of Chlamydomonas with plasmids encoding mutant psbA genes. Nucleotide sequences for nitrilase genes are disclosed in U.S. Pat. No. 4,810,648 to Stalker, and DNA molecules containing these genes are available under ATCC Accession Nos. 53435, 67441 and 67442. Cloning and expression of DNA coding for a glutathione S-transferase is described by Hayes et al, Biochem. J. 285: 173 (1992).

(D) Acetohydroxy acid synthase, which has been found to make plants that express this enzyme resistant to multiple types of herbicides, has been introduced into a variety of plants (see, e.g., Hattori et al. (1995) Mol Gen Genet 246:419). Other genes that confer tolerance to herbicides include: a gene encoding a chimeric protein of rat cytochrome P4507A1 and yeast NADPH-cytochrome P450 oxidoreductase (Shiota et al. (1994) Plant PhysiolPlant Physiol 106:17), genes for glutathione reductase and superoxide dismutase (Aono et al. (1995) Plant Cell Physiol 36:1687, and genes for various phosphotransferases (Datta et al. (1992) Plant Mol Biol 20:619).

(E) Protoporphyrinogen oxidase (protox) is necessary for the production of chlorophyll, which is necessary for all plant survival. The protox enzyme serves as the target for a variety of herbicidal compounds. These herbicides also inhibit growth of all the different species of plants present, causing their total destruction. The development of plants containing altered protox activity which are resistant to these herbicides are described in U.S. Pat. Nos. 6,288,306 B1; 6,282,837 B1; and 5,767,373; and international publication WO 01/12825, which are incorporated herein by reference in their entireties of all purposes.

抗害虫或抗疾病转基因（Transgenes that Confer Resistance to Pests or Disease and that Encode）

Transgenes that Confer Resistance to Pests or Disease and that Encode:

(A) Plant disease resistance genes. Plant defenses are often activated by specific interaction between the product of a disease resistance gene (R) in the plant and the product of a corresponding avirulence (Avr) gene in the pathogen. A plant variety can be transformed with cloned resistance gene to engineer plants that are resistant to specific pathogen strains. See, for example Jones et al., Science 266: 789 (1994) (cloning of the tomato Cf-9 gene for resistance to Cladosporium fulvum ); Martin et al., Science 262: 1432 (1993) (tomato Pto gene for resistance to Pseudomonas syringae pv. tomato encodes a protein kinase); Mindrinos et al., Cell 78: 1089 (1994) ( Arabidopsis RSP2 gene for resistance to Pseudomonas syringae ).

(B) A Bacillus thuringiensis protein, a derivative thereof or a synthetic polypeptide modeled thereon. See, for example, Geiser et al., Gene 48: 109 (1986), who disclose the cloning and nucleotide sequence of a Bt δ-endotoxin gene. Moreover, DNA molecules encoding δ-endotoxin genes can be purchased from American Type Culture Collection (Rockville, Md.), for example, under ATCC Accession Nos. 40098, 67136, 31995 and 31998. Other examples of Bacillus thuringiensis transgenes being genetically engineered are given in the following patents and hereby are incorporated by reference: U.S. Pat. Nos. 5,188,960; 5,689,052; 5,880,275; and WO 97/40162.

(C) A lectin. See, for example, the disclosure by Van Damme et al., Plant Molec. Biol. 24: 25 (1994), who disclose the nucleotide sequences of several Clivia miniata mannose-binding lectin genes.

(D) A vitamin-binding protein such as avidin. See PCT application US93/06487 the contents of which are hereby incorporated by reference. The application teaches the use of avidin and avidin homologues as larvicides against insect pests.

(E) An enzyme inhibitor, for example, a protease inhibitor or an amylase inhibitor. See, for example, Abe et al., J. Biol. Chem. 262: 16793 (1987) (nucleotide sequence of rice cysteine proteinase inhibitor), Huub et al., Plant Molec. Biol. 21: 985 (1993) (nucleotide sequence of cDNA encoding tobacco proteinase inhibitor I), and Sumitani et al., Biosci. Biotech. Biochem. 57: 1243 (1993) (nucleotide sequence of Streptomyces nitrosporeus α-amylase inhibitor) and U.S. Pat. No. 5,494,813.

(F) An insect-specific hormone or pheromone such as an ecdysteroid and juvenile hormone, a variant thereof, a mimetic based thereon, or an antagonist or agonist thereof. See, for example, the disclosure by Hammock et al., Nature 344: 458 (1990), of baculovirus expression of cloned juvenile hormone esterase, an inactivator of juvenile hormone.

(G) An insect-specific peptide or neuropeptide, which, upon expression, disrupts the physiology of the affected pest. For example, see the disclosures of Regan, J. Biol. Chem. 269: 9 (1994) (expression cloning yields DNA coding for insect diuretic hormone receptor), and Pratt et al., Biochem. Biophys. Res. Comm. 163: 1243 (1989) (an allostatin is identified in Diploptera puntata ). See also U.S. Pat. No. 5,266,317 to Tomalski et al., who disclose genes encoding insect-specific, paralytic neurotoxins.

(H) An insect-specific venom produced in nature by a snake, a wasp, etc. For example, see Pang et al., Gene 116: 165 (1992), for disclosure of heterologous expression in plants of a gene coding for a scorpion insectotoxic peptide.

(I) An enzyme responsible for an hyperaccumulation of a monterpene, a sesquiterpene, a steroid, hydroxamic acid, a phenylpropanoid derivative or another non-protein molecule with insecticidal activity.

(J) An enzyme involved in the modification, including the post-translational modification, of a biologically active molecule; for example, a glycolytic enzyme, a proteolytic enzyme, a lipolytic enzyme, a nuclease, a cyclase, a transaminase, an esterase, a hydrolase, a phosphatase, a kinase, a phosphorylase, a polymerase, an elastase, a chitinase and a glucanase, whether natural or synthetic. See PCT application WO 93/02197 in the name of Scott et al., which discloses the nucleotide sequence of a callase gene. DNA molecules which contain chitinase-encoding sequences can be obtained, for example, from the ATCC under Accession Nos. 39637 and 67152. See also Kramer et al., Insect Biochem. Molec. Biol. 23: 691 (1993), who teach the nucleotide sequence of a cDNA encoding tobacco hookworm chitinase, and Kawalleck et al., Plant Molec. Biol. 21: 673 (1993), who provide the nucleotide sequence of the parsley ubi4-2 polyubiquitin gene.

(K) A molecule that stimulates signal transduction. For example, see the disclosure by Botella et al., Plant Molec. Biol. 24: 757 (1994), of nucleotide sequences for mung bean calmodulin cDNA clones, and Griess et al., Plant Physiol. 104: 1467 (1994), who provide the nucleotide sequence of a maize calmodulin cDNA clone.

(L) A hydrophobic moment peptide. See PCT application WO95/16776 (disclosure of peptide derivatives of Tachyplesin which inhibit fungal plant pathogens) and PCT application WO95/18855 (teaches synthetic antimicrobial peptides that confer disease resistance), the respective contents of which are hereby incorporated by reference.

(M) A membrane permease, a channel former or a channel blocker. For example, see the disclosure by Jaynes et al., Plant Sci. 89: 43 (1993), of heterologous expression of a cecropin-βlytic peptide analog to render transgenic tobacco plants resistant to Pseudomonas solanacearum.

(N) A viral-invasive protein or a complex toxin derived therefrom. For example, the accumulation of viral coat proteins in transformed plant cells imparts resistance to viral infection and/or disease development effected by the virus from which the coat protein gene is derived, as well as by related viruses. See Beachy et al., Ann. Rev. Phytopathol. 28: 451 (1990). Coat protein-mediated resistance has been conferred upon transformed plants against alfalfa mosaic virus, cucumber mosaic virus, tobacco streak virus, potato virus X, potato virus Y, tobacco etch virus, tobacco rattle virus and tobacco mosaic virus. Id.

(O) An insect-specific antibody or an immunotoxin derived therefrom. Thus, an antibody targeted to a critical metabolic function in the insect gut would inactivate an affected enzyme, killing the insect. Cf. Taylor et al., Abstract #497, SEVENTH INT'L SYMPOSIUM ON MOLECULAR PLANT-MICROBE INTERACTIONS (Edinburgh, Scotland, 1994) (enzymatic inactivation in transgenic tobacco via production of single-chain antibody fragments).

(P) A virus-specific antibody. See, for example, Tavladoraki et al., Nature 366: 469 (1993), who show that transgenic plants expressing recombinant antibody genes are protected from virus attack.

(Q) A developmental-arrestive protein produced in nature by a pathogen or a parasite. Thus, fungal endo α-1,4-D-polygalacturonases facilitate fungal colonization and plant nutrient release by solubilizing plant cell wall homo-α-1,4-D-galacturonase. See Lamb et al., Bio/Technology 10: 1436 (1992). The cloning and characterization of a gene whichencodes a bean endopolygalacturonase-inhibiting protein is described by Toubart et al., Plant J. 2: 367 (1992).

(R) A developmental-arrestive protein produced in nature by a plant. For example, Logemann et al., Bio/Technology 10: 305 (1992), have shown that transgenic plants expressing the barley ribosome-inactivating gene have an increased resistance to fungal disease.

(S) Genes involved in the Systemic Acquired Resistance (SAR) Response and/or the pathogenesis related genes. Briggs, S., Current Biology, 5(2) (1995).

(T) Antifungal genes (Cornelissen and Melchers, Pl. Physiol. 101:709-712, (1993) and Parijs et al., Planta 183:258-264, (1991) and Bushnell et al., Can. J. of Plant Path. 20(2):137-149 (1998).

SUMMARY OF THE INVENTION

According to the invention, there is provided a novel inbred maize line, designated PH4CV. This invention thus relates to the seeds of inbred maize line PH4CV, to the plants of inbred maize line PH4CV, to plant parts of inbred maize line PH4CV, to methods for producing a maize plant produced by crossing the inbred maize line PH4CV with another maize plant, including a plant that is part of a synthetic or natural population, and to methods for producing a maize plant containing in its genetic material one or more transgenes and to the transgenic maize plants and plant parts produced by that method. This invention also relates to inbred maize lines and plant parts derived from inbred maize line PH4CV, to methods for producing other inbred maize lines derived from inbred maize line PH4CV and to the inbred maize lines and their parts derived by the use of those methods. This invention further relates to hybrid maize seeds, plants, and plant parts produced by crossing the inbred line PH4CV with another maize line.

Definitions for Area of Adaptability

When referring to area of adaptability, such term is used to describe the location with the environmental conditions that would be well suited for this maize line. Area of adaptability is based on a number of factors, for example: days to maturity, insect resistance, disease resistance, and drought resistance. Area of adaptability does not indicate that the maize line will grow in every location within the area of adaptability or that it will not grow outside the area.

Central Corn Belt: Iowa, Illinois, Indiana

Drylands: non-irrigated areas of North Dakota, South Dakota, Nebraska, Kansas, Colorado and Oklahoma

Eastern U.S.: Ohio, Pennsylvania, Delaware, Maryland, Virginia, and West Virginia

North central U.S.: Minnesota and Wisconsin

Northeast: Michigan, New York, Vermont, and Ontario and Quebec Canada

Northwest U.S.: North Dakota, South Dakota, Wyoming, Washington, Oregon, Montana, Utah, and Idaho

South central U.S.: Missouri, Tennessee, Kentucky, and Arkansas

Southeast U.S.: North Carolina, South Carolina, Georgia, Florida, Alabama, Mississippi, and Louisiana

Southwest U.S.: Texas, Oklahoma, New Mexico, and Arizona

Western U.S.: Nebraska, Kansas, Colorado, and California

Maritime Europe: France, Germany, Belgium and Austria

定义（Definitions ）

Certain definitions used in the specification are provided below. Also in the examples that follow, a number of terms are used herein. In order to provide a clear and consistent understanding of the specification and claims, including the scope to be given such terms, the following definitions are provided. NOTE: ABS is in absolute terms and % MN is percent of the mean for the experiments in which the inbred or hybrid was grown. PCT designates that the trait is calculated as a percentage. % NOT designates the percentage of plants that did not exhibit a trait. For example, STKLDG % NOT is the percentage of plants in a plot that were not stalk lodged. These designators will follow the descriptors to denote how the values are to be interpreted.

ABTSTK=ARTIFICIAL BRITTLE STALK. A count of the number of “snapped” plants per plot following machine snapping. A snapped plant has its stalk completely snapped at a node between the base of the plant and the node above the ear. Expressed as percent of plants that did not snap.

ALLELE. Any of one or more alternative forms of a genetic sequence. In a diploid cell or organism, the two alleles of a given sequence occupy corresponding loci on a pair of homologous chromosomes.

ANT ROT=ANTHRACNOSE STALK ROT ( Colletotrichum graminicola ). A 1 to 9 visual rating indicating the resistance to Anthracnose Stalk Rot. A higher score indicates a higher resistance.

BACKCROSSING. Process in which a breeder crosses a progeny line back to one of the parental genotypes one or more times.

BARPLT=BARREN PLANTS. The percent of plants per plot that was not barren (lack ears).

BREEDING. The genetic manipulation of living organisms.

BRTSTK=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.

CLDTST=COLD TEST. The percent of plants that germinate under cold test conditions.

CLN=CORN LETHAL NECROSIS. Synergistic interaction of maize chlorotic mottle virus (MCMV) in combination with either maize dwarf mosaic virus (MDMV-A or MDMV-B) or wheat streak mosaic virus (WSMV). A 1 to 9 visual rating indicating the resistance to Corn Lethal Necrosis. A higher score indicates a higher resistance.

COMRST=COMMON RUST ( Puccinia sorghi ). A 1 to 9 visual rating indicating the resistance to Common Rust. A higher score indicates a higher resistance.

D/D=DRYDOWN. This represents the relative rate at which a hybrid will reach acceptable harvest moisture compared to other hybrids on a 1-9 rating scale. A high score indicates a hybrid that dries relatively fast while a low score indicates a hybrid that dries slowly.

DIPERS= DIPLODIA EAR MOLD SCORES ( Diplodia maydis and Diplodia macrospora ). A 1 to 9 visual rating indicating the resistance to Diplodia Ear Mold. A higher score indicates a higher resistance.

DIPROT= DIPLODIA STALK ROT SCORE. Score of stalk rot severity due to Diplodia ( Diplodia maydis ). Expressed as a 1 to 9 score with 9 being highly resistant.

DRPEAR=DROPPED EARS. A measure of the number of dropped ears per plot and represents the percentage of plants that did not drop ears prior to harvest.

D/T=DROUGHT TOLERANCE. This represents a 1-9 rating for drought tolerance, and is based on data obtained under stress conditions. A high score indicates good drought tolerance and a low score indicates poor drought tolerance.

EARHT=EAR HEIGHT. The ear height is a measure from the ground to the highest placed developed ear node attachment and is measured in centimeters.

EARMLD=General Ear Mold. Visual rating (1-9 score) where a “1” is very susceptible and a “9” is very resistant. This is based on overall rating for ear mold of mature ears without determining the specific mold organism, and may not be predictive for a specific ear mold.

EARSZ=EAR SIZE. A 1 to 9 visual rating of ear size. The higher the rating the larger the ear size.

EBTSTK=EARLY BRITTLE STALK. A count of the number of “snapped” plants per plot following severe winds when the corn plant is experiencing very rapid vegetative growth in the V5-V8 stage. Expressed as percent of plants that did not snap.

ECB1LF=EUROPEAN CORN BORER FIRST GENERATION LEAF FEEDING ( Ostrinia nubilalis ). A 1 to 9 visual rating indicating the resistance to preflowering leaf feeding by first generation European Corn Borer. A higher score indicates a higher resistance.

ECB2IT=EUROPEAN CORN BORER SECOND GENERATION INCHES OF TUNNELING ( Ostrinia nubilalis ). Average inches of tunneling per plant in the stalk.

ECB2SC=EUROPEAN CORN BORER SECOND GENERATION ( Ostrinia nubilalis ). A 1 to 9 visual rating indicating post flowering degree of stalk breakage and other evidence of feeding by European Corn Borer, Second Generation. A higher score indicates a higher resistance.

ECBDPE=EUROPEAN CORN BORER DROPPED EARS ( Ostrinia nubilalis ). Dropped ears due to European Corn Borer. Percentage of plants that did not drop ears under second generation corn borer infestation.

EGRWTH=EARLY GROWTH. This is a measure of the relative height and size of a corn seedling at the 2-4 leaf stage of growth. This is a visual rating (1 to 9), with 1 being weak or slow growth, 5 being average growth and 9 being strong growth. Taller plants, wider leaves, more green mass and darker color constitute higher score.

ELITE INBRED. An inbred that contributed desirable qualities when used to produce commercial hybrids. An elite inbred may also be used in further breeding.

ERTLDG=EARLY ROOT LODGING. Early root lodging is the percentage of plants that do not root lodge prior to or around anthesis; plants that lean from the vertical axis at an approximately 30° angle or greater would be counted as root lodged.

ERTLPN=Early root lodging. An estimate of the percentage of plants that do not root lodge prior to or around anthesis; plants that lean from the vertical axis at an approximately 30° angle or greater would be considered as root lodged.

ERTLSC=EARLY ROOT LODGING SCORE. Score for severity of plants that lean from a vertical axis at an approximate 30-degree angle or greater, which typically results from strong winds prior to or around flowering recorded within 2 weeks of a wind event. Expressed as a 1 to 9 score with 9 being no lodging.

ESTCNT=EARLY STAND COUNT. This is a measure of the stand establishment in the spring and represents the number of plants that emerge on per plot basis for the inbred or hybrid.

EYESPT=Eye Spot ( Kabatiella zeae or Aureobasidium zeae ). A 1 to 9 visual rating indicating the resistance to Eye Spot. A higher score indicates a higher resistance.

FUSERS= FUSARIUM EAR ROT SCORE ( Fusarium moniliforme or Fusarium subglutinans ). A 1 to 9 visual rating indicating the resistance to Fusarium ear rot. A higher score indicates a higher resistance.

GDU=Growing Degree Units. Using the Barger Heat Unit Theory, which assumes that maize growth occurs in the temperature range 50° F.-86° F. and that temperatures outside this range slow down growth; the maximum daily heat unit accumulation is 36 and the minimum daily heat unit accumulation is 0. The seasonal accumulation of GDU is a major factor in determining maturity zones.

GDUSHD=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: GDU = ( Max . temp . + Min . temp . ) 2 - 50

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.

GDUSLK=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 emerg

定义（Definitions ）- 续

KSZDCD=KERNEL SIZE DISCARD. The percent of discard seed; calculated as the sum of discarded tip kernels and extra large kernels.

LINKAGE. Refers to a phenomenon wherein alleles on the same chromosome tend to segregate together more often than expected by chance if their transmission was independent.

LINKAGE DISEQUILIBRIUM. Refers to a phenomenon wherein alleles tend to remain together in linkage groups when segregating from parents to offspring, with a greater frequency than expected from their individual frequencies.

L/POP=YIELD AT LOW DENSITY. Yield ability at relatively low plant densities on a 1-9 relative system with a higher number indicating the hybrid responds well to low plant densities for yield relative to other hybrids. A 1, 5, and 9 would represent very poor, average, and very good yield response, respectively, to low plant density.

LRTLDG=LATE ROOT LODGING. Late root lodging is the percentage of plants that do not root lodge after anthesis through harvest; plants that lean from the vertical axis at an approximately 30° angle or greater would be counted as root lodged.

LRTLPN=LATE ROOT LODGING. Late root lodging is an estimate of the percentage of plants that do not root lodge after anthesis through harvest; plants that lean from the vertical axis at an approximately 30° angle or greater would be considered as root lodged.

LRTLSC=LATE ROOT LODGING SCORE. Score for severity of plants that lean from a vertical axis at an approximate 30-degree angle or greater which typically results from strong winds after flowering. Recorded prior to harvest when a root-lodging event has occurred. This lodging results in plants that are leaned or “lodged” over at the base of the plant and do not straighten or “goose-neck” back to a vertical position. Expressed as a 1 to 9 score with 9 being no lodging.

MDMCPX=MAIZE DWARF MOSAIC COMPLEX (MDMV=Maize Dwarf Mosaic Virus and MCDV=Maize Chlorotic Dwarf Virus). A 1 to 9 visual rating indicating the resistance to Maize Dwarf Mosaic Complex. A higher score indicates a higher resistance.

MST=HARVEST MOISTURE. The moisture is the actual percentage moisture of the grain at harvest.

MSTADV=MOISTURE ADVANTAGE. The moisture advantage of variety #1 over variety #2 as calculated by: MOISTURE of variety #2MOISTURE of variety #1=MOISTURE ADVANTAGE of variety #1.

NLFBLT=Northern Leaf Blight ( Helminthosporium turcicum or Exserohilum turcicum ). A 1 to 9 visual rating indicating the resistance to Northern Leaf Blight. A higher score indicates a higher resistance.

OILT=GRAIN OIL. Absolute value of oil content of the kernel as predicted by Near-infrared Transmittance and expressed as a percent of dry matter.

PEDIGREE DISTANCE. Relationship among generations based on their ancestral links as evidenced in pedigrees. May be measured by the distance of the pedigree from a given starting point in the ancestry.

PLTHT=PLANT HEIGHT. This is a measure of the height of the plant from the ground to the tip of the tassel in centimeters.

POLSC=POLLEN SCORE. A 1 to 9 visual rating indicating the amount of pollen shed. The higher the score the more pollen shed.

POLWT=POLLEN WEIGHT. This is calculated by dry weight of tassels collected as shedding commences minus dry weight from similar tassels harvested after shedding is complete.

POP K/A=PLANT POPULATIONS. Measured as 1000s per acre.

POP ADV=PLANT POPULATION ADVANTAGE. The plant population advantage of variety #1 over variety #2 as calculated by PLANT POPULATION of variety #2PLANT POPULATION of variety #1=PLANT POPULATION ADVANTAGE of variety #1.

PRM=PREDICTED RELATIVE MATURITY. This trait, predicted relative maturity, is based on the harvest moisture of the grain. The relative maturity rating is based on a known set of checks and utilizes standard linear regression analyses and is also referred to as the Comparative Relative Maturity Rating System that is similar to the Minnesota Relative Maturity Rating System.

PRMSHD=A relative measure of the growing degree units (GDU) required to reach 50% pollen shed. Relative values are predicted values from the linear regression of observed GDU's on relative maturity of commercial checks.

PROT=GRAIN PROTEIN. Absolute value of protein content of the kernel as predicted by Near-Infrared Transmittance and expressed as a percent of dry matter.

RTLDG=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.

RTLADV=ROOT LODGING ADVANTAGE. The root lodging advantage of variety #1 over variety #2.

SCTGRN=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.

SDGVGR=SEEDLING VIGOR. This is the visual rating (1 to 9) of the amount of vegetative growth after emergence at the seedling stage (approximately five leaves). A higher score indicates better vigor.

SEL IND=SELECTION INDEX. The selection index gives a single measure of the hybrid's worth based on information for up to five traits. A maize breeder may utilize his or her own set of traits for the selection index. One of the traits that is almost always included is yield. The selection index data presented in the tables represent the mean value averaged across testing stations.

SLFBLT=SOUTHERN LEAF BLIGHT ( Helminthosporium maydis or Bipolaris maydis ). A 1 to 9 visual rating indicating the resistance to Southern Leaf Blight. A higher score indicates a higher resistance.

SOURST=SOUTHERN RUST ( Puccinia polysora ). A 1 to 9 visual rating indicating the resistance to Southern Rust. A higher score indicates a higher resistance.

STAGRN=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.

STDADV=STALK STANDING ADVANTAGE. The advantage of variety #1 over variety #2 for the trait STK CNT.

STKCNT=NUMBER OF PLANTS. This is the final stand or number of plants per plot.

STKLDG=STALK LODGING REGULAR. This is the percentage of plants that did not stalk lodge (stalk breakage) at regular harvest (when grain moisture is between about 20 and 30%) as measured by either natural lodging or pushing the stalks and determining the percentage of plants that break below the ear.

STKLDL=LATE STALK LODGING. This is the percentage of plants that did not stalk lodge (stalk breakage) at or around late season harvest (when grain moisture is between about 15 and 18%) as measured by either natural lodging or pushing the stalks and determining the percentage of plants that break below the ear.

STKLDS=STALK LODGING SCORE. A plant is considered as stalk lodged if the stalk is broken or crimped between the ear and the ground. This can be caused by any or a combination of the following: strong winds late in the season, disease pressure within the stalks, ECB damage or genetically weak stalks. This trait should be taken just prior to or at harvest. Expressed on a 1 to 9 scale with 9 being no lodging.

STLPCN=STALK LODGING REGULAR. This is an estimate of the percentage of plants that did not stalk lodge (stalk breakage) at regular harvest (when grain moisture is between about 20 and 30%) as measured by either natural lodging or pushing the stalks and determining the percentage of plants that break below the ear.

STRT=GRAIN STARCH. Absolute value of starch content of the kernel as predicted by Near-infrared Transmittance and expressed as a percent of dry matter.

STWWLT=Stewart's Wilt ( Erwinia stewartii ). A 1 to 9 visual rating indicating the resistance to Stewart's Wilt. A higher score indicates a higher resistance.

TASBLS=TASSEL BLAST. A 1 to 9 visual rating was used to measure the degree of blasting (necrosis due to heat stress) of the tassel at the time of flowering. A 1 would indicate a very high level of blasting at time of flowering, while a 9 would have no t

BACKGROUND OF THE INVENTION

The goal of plant breeding is to combine in a single variety or hybrid, various desirable traits. For field crops, these traits may include resistance to diseases and insects, tolerance to heat and drought, reducing the time to crop maturity, greater yield, and better agronomic quality. With mechanical harvesting of many crops, uniformity of plant characteristics such as germination and stand establishment, growth rate, maturity, and plant and ear height, is important.

Field crops are bred through techniques that take advantage of the plant's method of pollination. A plant is self-pollinated if pollen from one flower is transferred to the same or another flower of the same plant. A plant is sib-pollinated when individuals within the same family or line are used for pollination. A plant is cross-pollinated if the pollen comes from a flower on a different plant from a different family or line. The terms “cross-pollination” and “out-cross” as used herein do not include self-pollination or sib-pollination.

Plants that have been self-pollinated and selected for type for many generations become homozygous at almost all gene loci and produce a uniform population of true breeding progeny. A cross between two different homozygous lines produces a uniform population of hybrid plants that may be heterozygous for many gene loci. A cross of two plants, each heterozygous at a number of gene loci will produce a population of hybrid plants that differ genetically and will not be uniform.

Maize ( zea mays L.), often referred to as corn in the United States, can be bred by both self-pollination and cross-pollination techniques. Maize has separate male and female flowers on the same plant, located on the tassel and the ear, respectively. Natural pollination occurs in maize when wind blows pollen from the tassels to the silks that protrude from the tops of the ears.

A reliable method of controlling male fertility in plants offers the opportunity for improved plant breeding. This is especially true for development of maize hybrids, which relies upon some sort of male sterility system. There are several ways in which a maize plant can be manipulated so that it is male sterile. These include use of manual or mechanical emasculation (or detasseling), use of cytoplasmic genetic or nuclear genetic male sterility, use of gametocides and is the like.

Hybrid maize seed is typically produced by a male sterility system incorporating manual or mechanical detasseling. Alternate strips of two maize inbreds are planted in a field, and the pollen-bearing tassels are removed from one of the inbreds (female). Provided that there is sufficient isolation from sources of foreign maize pollen, the ears of the detasseled inbred will be fertilized only from the other inbred (male), and the resulting seed is therefore hybrid and will form hybrid plants.

The laborious detasseling process can be avoided by using cytoplasmic male-sterile (CMS) inbreds. Plants of a CMS inbred are male sterile as a result of factors resulting from the cytoplasmic, as opposed to the nuclear, genome. Thus, this characteristic is inherited exclusively through the female parent in maize plants, since only the female provides cytoplasm to the fertilized seed. CMS plants are fertilized with pollen from another inbred that is not male-sterile. Pollen from the second inbred may or may not contribute genes that make the hybrid plants male-fertile. The same hybrid seed, a portion produced from detasseled fertile maize and a portion produced using the CMS system, can be blended to insure that adequate pollen loads are available for fertilization when the hybrid plants are grown.

There are several methods of conferring genetic male sterility available, such as multiple mutant genes at separate locations within the genome that confer male sterility, as disclosed in U.S. Pat. Nos. 4,654,465 and 4,727,219 to Brar et al. and chromosomal translocations as described by Patterson in U.S. Pat. Nos. 3,861,709 and 3,710,511. These and all patents, patent applications and publications referred to herein are incorporated by reference. In addition to these methods, Albertsen et al., of Pioneer Hi-Bred, U.S. Pat. No. 5,432,068, have developed a system of nuclear male sterility which includes: identifying a gene which is critical to male fertility; silencing this native gene which is critical to male fertility; removing the native promoter from the essential male fertility gene and replacing it with an inducible promoter; inserting this genetically engineered gene back into the plant; and thus creating a plant that is male sterile because the inducible promoter is not “on” resulting in the male fertility gene not being transcribed. Fertility is restored by inducing, or turning “on”, the promoter, which in turn allows the gene that confers male fertility to be transcribed.

These, and the other methods of conferring genetic male sterility in the art, each possess their own benefits and drawbacks. Some other methods use a variety of approaches such as delivering into the plant a gene encoding a cytotoxic substance associated with a male tissue specific promoter or an antisense system in which a gene critical to fertility is identified and an antisense to that gene is inserted in the plant (see: Fabinjanski, et al. EPO 89/3010153.8 publication no. 329,308 and PCT application PCT/CA90/00037 published as WO 90/08828).

Another system for controlling male sterility makes use of gametocides. Gametocides are not a genetic system, but rather a topical application of chemicals. These chemicals affect cells that are critical to male fertility. The application of these chemicals affects fertility in the plants only for the growing season in which the gametocide is applied (see Carlson, Glenn R., U.S. Pat. No. 4,936,904). Application of the gametocide, timing of the application and genotype specificity often limit the usefulness of the approach and it is not appropriate in all situations.

玉米杂交系的开发 （Development of Maize Hybrids）

A single cross maize hybrid results from the cross of two inbred lines, each of which has a genotype that complements the genotype of the other. The hybrid progeny of the first generation is designated F 1 . In the development of commercial hybrids in a maize plant breeding program, only the F 1 hybrid plants are sought. 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 maize hybrid in a maize plant breeding program involves three steps: (1) the selection of plants from various germplasm pools for initial breeding crosses; (2) the selfing of the selected plants from the breeding crosses for several generations to produce a series of inbred lines, which, although different from each other, breed true and are highly uniform; and (3) crossing the selected inbred lines with different inbred lines to produce the hybrids. During the inbreeding process in maize, the vigor of the lines decreases. Vigor is restored when two different inbred lines are crossed to produce the hybrid. An important consequence of the homozygosity and homogeneity of the inbred lines is that the hybrid between a defined pair of 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 1 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). A three-way cross hybrid is produced from three inbred lines where two of the inbred lines are crossed (A×B) and then the resulting F 1 hybrid is crossed with the third inbred (A×B)×C. Much of the hybrid vigor and uniformity exhibited by F 1 hybrids is lost in the next generation (F 2 ). Consequently, seed produced from hybrids is not used for planting stock.

Hybrid seed production requires elimination or inactivation of pollen produced by the female parent. Incomplete removal or inactivation of the pollen provides the potential for self-pollination. This inadvertently self-pollinated seed may be unintentionally harvested and packaged with hybrid seed. Also, because the male parent is grown next to the female parent in the field there is the very low probability that the male selfed seed could be unintentionally harvested and packaged with the hybrid seed. Once the seed from the hybrid bag is planted, it is possible to identify and select these self-pollinated plants. These self-pollinated plants will be genetically equivalent to one of the inbred lines used to produce the hybrid. Though the possibility of inbreds being included hybrid seed bags exists, the occurrence is very low because much care is taken to avoid such inclusions. It is worth noting that hybrid seed is sold to growers for the production of grain or forage and not for breeding or seed production.

These self-pollinated plants can be identified and selected by one skilled in the art due to their decreased vigor when compared to the hybrid. Inbreds are identified by their less vigorous appearance for vegetative and/or reproductive characteristics, including shorter plant height, small ear size, ear and kernel shape, cob color, or other characteristics.

Identification of these self-pollinated lines can also be accomplished through molecular marker analyses. See, “The Identification of Female Selfs in Hybrid Maize: A Comparison Using Electrophoresis and Morphology”, Smith, J. S. C. and Wych, R. D., Seed Science and Technology 14, pp. 1-8 (1995), the disclosure of which is expressly incorporated herein by reference. Through these technologies, the homozygosity of the self-pollinated line can be verified by analyzing allelic composition at various loci along the genome. Those methods allow for rapid identification of the invention disclosed herein. See also, “Identification of Atypical Plants in Hybrid Maize Seed by Postcontrol and Electrophoresis” Sarca, V. et al., Probleme de Genetica Teoritica si Aplicata Vol. 20 (1) p. 29-42.

As is readily apparent to one skilled in the art, the foregoing are only some of the various ways by which the inbred can be obtained by those looking to use the germplasm. Other means are available, and the above examples are illustrative only.

Maize is an important and valuable field crop. Thus, a continuing goal of plant breeders is to develop high-yielding maize hybrids that are agronomically sound based on stable inbred lines. The reasons for this goal are obvious: to maximize the amount of grain produced with the inputs used and minimize susceptibility of the crop to pests and environmental stresses. To accomplish this goal, the maize breeder must select and develop superior inbred parental lines for producing hybrids. This requires identification and selection of genetically unique individuals that occur in a segregating population. The segregating population is the result of a combination of crossover events plus the independent assortment of specific combinations of alleles at many gene loci that results in specific genotypes. The probability of selecting any one individual with a specific genotype from a breeding cross is infinitesimal due to the large number of segregating genes and the unlimited recombinations of these genes, some of which may be closely linked. However, the genetic variation among individual progeny of a breeding cross allows for the identification of rare and valuable new genotypes. These new genotypes are neither predictable nor incremental in value, but rather the result of manifested genetic variation combined with selection methods, environments and the actions of the breeder. Once identified, it is possible to utilize routine and predictable breeding methods to develop progeny that retain the rare and valuable new genotypes developed by the initial breeder.

Even if the entire genotypes of the parents of the breeding cross were characterized and a desired genotype known, only a few if any individuals having the desired genotype may be found in a large segregating F 2 population. It would be very unlikely that a breeder of ordinary skill in the art would able to recreate the same line twice from the very same original parents, as the breeder is unable to direct how the genomes combine or how they will interact with the environmental conditions. This unpredictability results in the expenditure of large amounts of research resources in the development of a superior new maize inbred line. Once such a line is developed its value to society is substantial since it is important to advance the germplasm base as a whole in order to maintain or improve traits such as yield, disease resistance, pest resistance and plant performance in extreme conditions.

A breeder uses various methods to help determine which plants should be selected from the segregating populations and ultimately which inbred lines will be used to develop hybrids for commercialization. In addition to the knowledge of the germplasm and other skills the breeder uses, a part of the selection process is dependent on experimental design coupled with the use of statistical analysis. Experimental design and statistical analysis are used to help determine which plants, which family of plants, and finally which inbred lines and hybrid combinations are significantly better or different for one or more traits of interest. Experimental design methods are used to assess error so that differences between two inbred lines or two hybrid lines can be more accurately determined. Statistical analysis includes the calculation of mean values, determination of the statistical significance of the sources of variation, and the calculation of the appropriate variance components. Either a five or a one percent significance level is customarily used to determine whether a difference that occurs for a given trait is real or due to the environment or experimental error.

One of ordinary skill in the art of plant breeding would know how to evaluate the traits of two plant varieties to determine if there is no significant difference between the two traits expressed by those varieties. For example, see Fehr, Walt, Principles of Cultivar Development, p. 261-286 (1987) which is incorporated herein by reference. Mean trait values may be used to determine whether trait differences are significant, and preferably the traits are measured on plants grown under the same environmental conditions.

Combining ability of a line, as well as the performance of the line per se, is a factor in the selection of improved maize inbreds. Combining ability refers to a line's contribution as a parent when crossed with other lines to form hybrids. The hybrids formed for the purpose of selecting superior lines are designated testcrosses. One way of measuring combining ability is by using breeding values. Breeding values are based in part on the overall mean of a number of testcrosses. This mean is then adjusted to remove environmental effects and it is adjusted for known genetic relationships among the lines.

Development of Maize Inbred Lines

The use of male sterile inbreds is but one factor in the production of maize hybrids. Plant breeding techniques known in the art and used in a maize plant breeding program include, but are not limited to, recurrent selection, backcrossing, pedigree breeding, restriction fragment length polymorphism enhanced selection, genetic marker enhanced selection, making double haploids, and transformation. Often a combination of these techniques is used. The development of maize hybrids in a maize plant breeding program requires, in general, the development of homozygous inbred lines, the crossing of these lines, and the evaluation of the crosses.

Maize plant breeding programs combine the genetic backgrounds from two or more inbred lines or various other germplasm sources into breeding populations 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. Plant breeding and hybrid development, as practiced in a maize plant breeding program developing significant genetic advancement, are expensive and time-consuming processes.

Pedigree breeding starts with the crossing of two genotypes, such as two elite inbred lines, 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 parents do not provide all the desired characteristics, other sources can be included in the breeding population. In the pedigree method, superior plants are selfed and selected in successive filial generations. In the succeeding filial 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 successive filial generations of selfing and selection is practiced: F 1 →F 2 ; F 2 →F 3 ; F 3 →F 4 ; F 4 →F 5 , etc. After a sufficient amount of inbreeding, successive filial generations will serve to increase seed of the developed inbred. Preferably, an inbred line comprises homozygous alleles at about 95% or more of its loci.

Backcrossing can be used to improve an inbred line and a hybrid that is made using those inbreds. Backcrossing can be used to transfer a specific desirable trait from one line, the donor parent, to an inbred called the recurrent parent which has overall good agronomic characteristics yet lacks that desirable trait. This transfer of the desirable trait into an inbred with overall good agronomic characteristics can be accomplished by first crossing a recurrent parent and a donor parent (non-recurrent parent). The progeny of this cross is then mated back to the recurrent parent followed by selection in the resultant progeny for the desired trait to be transferred from the non-recurrent parent as well as selection for the characteristics of the recurrent parent. Typically after four or more backcross generations with selection for the desired trait and the characteristics of the recurrent parent, the progeny will contain essentially all genes of the recurrent parent except for the genes controlling the desired trait. However, the number of backcross generations can be less if molecular markers are used during selection or elite germplasm is used as the donor parent. The last backcross generation is then selfed to give pure breeding progeny for the gene(s) being transferred. Backcrossing can also be used in conjunction with pedigree breeding to develop new inbred lines. For example, an F1 can be created that is backcrossed to one of its parent lines to create a BC1, BC2, BC3, etc. Progeny are selfed and selected so that the newly developed inbred has many of the attributes of the recurrent parent and some of the desired attributes of the non-recurrent parent. This approach leverages the value and strengths of the recurrent parent for use in new hybrids and breeding which has very significant value for a breeder.

Recurrent selection is a method used in a plant breeding program to improve a population of plants. The method entails individual plants cross-pollinating with each other to form progeny, which are then grown. The superior progeny are then selected by any number of methods, which include individual plant, half-sib progeny, full-sib progeny, selfed progeny and topcrossing. The selected progeny are cross-pollinated with each other to form progeny for another population. This population is planted and again superior plants are selected to cross-pollinate with each other. Recurrent selection is a cyclical process and therefore can be repeated as many times as desired. The objective of recurrent selection is to improve the traits of a population. The improved population can then be used as a source of breeding material to obtain inbred lines to be used in hybrids or used as parents for a synthetic cultivar. A synthetic cultivar is the resultant progeny formed by the intercrossing of several selected inbreds. Mass selection is a useful technique when used in conjunction with molecular marker enhanced selection.

Mutation breeding is one of the many methods of introducing new traits into inbred lines. Mutations that occur spontaneously or are artificially induced can be useful sources of variability for a plant breeder. The goal of artificial mutagenesis is to increase the rate of mutation for a desired characteristic. Mutation rates can be increased by many different means including temperature, long-term seed storage, tissue culture conditions, radiation; such as X-rays, Gamma rays (e.g. cobalt 60 or cesium 137), neutrons, (produce of nuclear fission by uranium 235 on an atomic reactor), Beta radiation (emitted from radioisotopes such as phosphorus 32 or carbon 14), or ultraviolet radiation (preferably from 2500 to 2900 nm), or chemical mutagens (such as base analogues (5-bromo-uracil), related compounds (8-ethoxy caffeine), antibiotics (streptonigrin), alkylating agents (sulfur mustards, nitrogen mustards, epoxides, ethylenamines, sulfates, sulfonates, sulfones, lactones), azide, hydroxylamine, nitrous acid, or acridines. Once a desired trait is observed through mutagenesis the trait may then be incorporated into existing germplasm by traditional breeding techniques. Details of mutation breeding can be found in “Principals of Cultivar Development” Fehr, 1993 Macmillan Publishing Company the disclosure of which is incorporated herein by reference.

Molecular markers, which includes markers identified through the use of techniques such as Isozyme Electrophoresis, Restriction Fragment Length Polymorphisms (RFLPs), Randomly Amplified Polymorphic DNAs (RAPDs), Arbitrarily Primed Polymerase Chain Reaction (AP-PCR), DNA Amplification Fingerprinting (DAF), Sequence Characterized Amplified Regions (SCARs), Amplified Fragment Length Polymorphisms (AFLPs), Simple Sequence Repeats (SSRs) and Single Nucleotide Polymorphisms (SNPs), may be used in plant breeding methods. One use of molecular markers is Quantitative Trait Loci (QTL) mapping. QTL mapping is the use of markers, which are known to be closely linked to alleles that have measurable effects on a quantitative trait. Selection in the breeding process is based upon the accumulation of markers linked to the positive effecting alleles and/or the elimination of the markers linked to the negative effecting alleles from the plant's genome.

Molecular markers can also be used during the breeding process for the selection of qualitative traits. For example, markers closely linked to alleles or markers containing sequences within the actual alleles of interest can be used to select plants that contain the alleles of interest during a backcrossing breeding program. The markers can also be used to select for the genome of the recurrent parent and against the genome of the donor parent. Using this procedure can minimize the amount of genome from the donor parent that remains in the selected plants. It can also be used to reduce the number of crosses back to the recurrent parent needed in a backcrossing program. The use of molecular markers in the selection process is often called genetic marker enhanced selection.

The production of double haploids can also be used for the development of inbreds in the breeding program. Double haploids are produced by the doubling of a set of chromosomes (1N) from a heterozygous plant to produce a completely homozygous individual. For example, see Wan et al., “Efficient Production of Doubled Haploid Plants Through Colchicine Treatment of Anther-Derived Maize Callus”, Theoretical and Applied Genetics, 77:889-892, 1989. This can be advantageous because the process omits the generations of selfing needed to obtain a homozygous plant from a heterozygous source.

FIELD OF THE INVENTION

This invention is in the field of maize breeding, specifically relating to an inbred maize line designated PH4CV.

发明背景

对植物育种的目标是, 把各种理想特性, 结合在一个单一品种或杂交种。对于大田作物，这些特质可能包括抗病虫害，耐炎热和干旱，减少农作物成熟时间，提高产量，质量和更好的农艺性状。随着许多农作物机械收获, 均匀的特征, 如植物发芽和群立，成长率，成熟度，以及植物和穗位高，是重要的。

田间作物繁殖, 可以利用植物的授粉方法的技术。一种植物是自花授粉，如果从一花花粉转移到另一个相同或同一植物的花朵。一种植物是同胞授粉，当同一系内个体之间相互授粉。一种植物是异系授粉，如果花粉来自一个不同的系的不同的植株。这里所用术语“交叉授粉”和“外交”并不包括自花授粉或同胞花授粉。

植物经过许多代, 自花授粉和选型，成为在几乎所有基因位点纯合型的, 产生一个真正的繁育后代的单一种群。两种不同的纯系交叉产生的杂种植株的单一种群，可能在许多基因位点是杂合的。在多个基因位点杂合的, 两种植物的杂交，将产生一个杂合植物的种群，它是基因和表形都不单一的杂种植株。

玉米（玉米属），通常在美国称为玉米，可以通过自花授粉和异花授粉技术培育。玉米在同一植株上有单独分开的雄花和雌花, 分别位于流苏和穗上。玉米天然授粉发生时, 风把雄穗花粉吹到突出于玉米穗的顶部的丝上。

一个提供可靠控制植物雄性生育的方法，带来提高植物育种的机会。玉米杂交品种的开发，真正依靠某种雄性不育系统。有几种方式可以调控一个玉米植物，使之不育。这些方式包括人工或机械去势（或去顶端雄穗），细胞质遗传或核基因雄性不育的使用方式，使用杀雄剂或类似的方式。

杂交玉米种子的产生通常是通过包含人工或机械去顶端雄穗的去雄系统。两个玉米自交系间隔种植在一块地里，把其中一个玉米系的带花粉雄穗去掉（雌株）。只要对外源玉米花粉有足够的隔离，去顶端雄穗的自交系的玉米穗只能被另一间隔种植的自交系的玉米株致孕(雄株），由此产生的种子是杂交的，并且此种子形成杂交植株。

使用细胞质雄性不育（CMS）的自交系, 可避免费力繁琐的去顶端雄穗的过程。CMS自交系的植株是雄性不育的, 来源于细胞质，而不是核的基因的多种因素。因此，这一特点是完全通过玉米植株母本继承的，因为只有雌株提供受精种子的细胞质。CMS不育系植株通过来自另一个非不育自交系的花粉而受孕。从第二个自交系的花粉可能会或不会贡献使杂合植株成为雄性可育的的基因。同样的杂交种子，一部分来自去顶端雄穗的玉米, 另一部分来自采用CMS系统得到的，可以混合起来，以保证有足够量的花粉用于杂合种株长成时的致孕。

有很多种赋予基因雄性不育的方法可供选择，比如布拉尔等人在美国专利4654465和4727219中披露的位于基因组不同点位的多种变异基因, 和帕特森在美国专利3861709和3710511中描述了染色体易位, 可造成遗传雄性不育。这些专利以及这里所引用的所有专利，专利申请和出版物均供参考。除了这些方法，先锋公司的阿尔伯特森等人的美国专利5432068，已经开发出核基因雄性不育的系统包括：

发现确定了一个和雄性生殖至关重要的基因;

哑化这个和雄性生育关键的内源性基因;

从重要的雄性生育基因中去掉内源性的启动子, 代之以一个可诱导的启动子;

把这个基因工程改造过的基因插入到植物中;

从而创造一种植物雄性不育的植株, 因为可诱导的启动子处于关闭状态, 导致雄性生育基因不能被转录。通过诱导, 或”打开”, 启动子, 从而使雄性生育的基因被转录, 生育能力得到恢复。

这些方法，和造成基因雄性不育的其他方法，每个拥有自己的优点和缺点。一些其他方法使用各式各样的手段，比如给植物移入一段基因, 这个基因编码一个和雄性组织特异性启动子相关的细胞毒性物质, 或者是反义基因系统，找到与生育相关的基因, 把它的反义基因插入到植株中（见：Fabinjanski，等。EPO89/3010153.8出版物号329308和PCT申请PCT/CA90/00037作为90/08828出版）。

另一个控制雄性不育的系统，利用的是杀雄剂。 杀雄剂不是基因系统，而是一个化学品外用。这些化学物质影响和雄性生育能力相关的关键细胞。这些化学品的应用只影响施用杀雄剂的生长季节植物的生育能力.（见卡尔森，格伦河，美国专利号4936904）。对杀雄剂的应用，应用时间和基因型特异性往往限制了该方法的有效性, 并且它不能用于所有的情况。

• 【合作】玉米种子 PH4CV专利翻译合作

外链出处

我国部分地区大老鼠绝迹 被指与转基因玉米有关

外链出处

玉米自交系的开发

雄性不育自交系的利用仅是在玉米杂交种生产中的要素之一。本专利已知和应用的植物育种技术在玉米育种方案中, 包括但不限于, 轮回选择，回交，系谱选育，限制性片段长度多态性提高甄选，遗传标记提高甄选，加倍单倍体和改造。通常，这些技术的组合被加以使用。在玉米育种方案中, 玉米杂交种的开发需要，总体来讲包括，开发纯合自交系，这些纯合自交系的互交，以及对互交作物的评价。

玉米育种方案，结合了从两个或多个自交系的遗传背景或其他各种来源为种质的育种种群, 从中新自交系经过自交和选择所需的表型种群得到开发。新自交系与其他自交系交叉育种, 在这些杂交种中进行评估，以确定其中哪些具有商业潜力。在玉米育种项目中为开发具有显着的遗传进展的品种, 所进行的植物育种和杂交开发，是价格昂贵，而且费时的过程。

良种繁殖开始于两个基因型的互交，例如两个优良自交系，每个自交系可以有一个或多个在其他自交系缺乏或互补的理想特性。如果这两个原始父本母本没有提供所有需要的特点，可以引入其他来源的种群育种。在系谱选育法中，优越的植株体自交和连续进行子代选择。在随后子代的选育中, 由于自花授粉和选择的结果, 杂合条件下的品系逐渐成为纯合自交的品系。通常在系谱选育种法中，连续进行5个或更多的子代自交和选择：F1→F2，F2→F 3，F3→F4，F4→F5, 等. 经过足够数量的近亲育种，连续子代将有助于提高被开发的自交系种子的质量。最好是，这个自交系在95％或以上的位点包含纯合等位基因。

回交可以用来改善一种自交系和由那些自交系形成的杂交系。回交可以从供体亲本, 转移一特定所需的特征，到一个被称为轮回亲本自交系的品系上, 这一轮回亲本自交系从总体上具有良好的农艺性状, 但是还缺乏那一理想的特征。这个把所需特征转移到一个具有整体良好的农艺性状自交系的过程, 可以通过首先把一个轮回亲本和供体亲本（非轮回亲本）互交而实现。这种交叉交配的后代，然后返回与轮回亲本进行交配, 然后从得到的后代选择来自非轮回亲本的所需的特性, 和轮回亲本的特征。通常经过从轮回亲本选择所需的特性的四代或更多代回交, 后代将包含除了控制轮回亲本所需基因以外的轮回亲本的所有基因。然而，如果能够在选种中使用分子标记, 或使用优异种质为供体亲本, 就可以减少回交子代的数量。最后回交得到的一代进行自交，就能得到带有被转移基因的纯种后代。回交也可与系谱选育结合使用，用于开发新的自交系。例如，可以产生一个F1, 它与其亲本之一回交，就可产生BC1，BC2，BC3代等. 后代经过自交和选择，这样新生成的自交系具有许多轮回亲本的属性和一些来自非轮回亲本的所需要的属性。这种方法利用了在新的杂交育种中对于育种者具有显著价值的轮回亲本的使用价值和优势。

轮回选择是在育种方案中, 用以提高植物种群使用的一个方法。该方法需要单株交叉相互授粉，形成子代，然后再生长。优越的后代，然后通过以下任何的方法加以选择，包括单体种植，半同胞子代，全同胞子代，自交后代和顶交。选定的后代相互授粉，形成另一个植物后代。此优势植物经过种植，良种再次经过选择并且交叉相互授粉。回选是一个循环过程，因此可以根据需要重复多次的。轮回选择的目标是改善种群的特点。改进后的种群可以被用来作为获得杂交后代的自交系的育种材料的来源, 或者作为一种合成品种的亲本。一个合成品种是由若干自交系相互交叉育种产生的后代。当与分子标记增强的选择性共用时, 广选就成为一种有用的技术。

诱变育种是许多能引入新的自交系性状的方法之一。自发或人为引起的突变是植物育种者获得可变性的有用的来源。人工诱变的目标是增加一个理想特性的突变率。增加突变率可通过许多不同的方法, 包括温度，长期种子贮存，组织培养条件，辐射，如X射线，伽玛射线（如钴60或铯137），中子，（在一个原子反应堆产生的铀235核裂变的产物），β辐射（由放射性同位素磷32或碳14放射的），或紫外线辐射（最好是2500至2900纳米的辐射），或化学诱变剂（如碱基类似物（5溴尿嘧啶），相关化合物（8 -乙氧基咖啡因），抗生素（链黑菌素），烷基化剂（硫芥气，氮芥，环氧化物，乙酰胺，硫酸盐，磺酸盐，砜，内酯），叠氮化物，羟胺，亚硝酸，或吖啶的。一旦通过诱变的性状观察得到理想性状, 此性状便可通过传统育种技术被纳入现有的种质中。诱变育种的详情，可参照这里披露的文献, 由费荷编辑的“种植品种发展原理”，1993年麦克米伦出版公司。

分子标记，包括如下的技术，如同工酶电泳，限制性片段长度多态性（RFLPs），随机扩增多态DNAs（RAPDs），随机引物聚合酶链反应（AP- PCR）技术，扩增的DNA指纹图谱法（DAF） ，特征扩增区序列（SCARs），扩增片段长度多态性（AFLPs），简单序列重复（SSRs）和单核苷酸多态性（SNPs），都是可用于植物育种的方法。其中一个分子标志物的用处是定量性状位点（QTL）定位。 QTL定位就是使用分子标记，这些分子标记和可定量测量性状的等位基因密切相关。在育种过程中的种子选择, 是通过根据植物的基因组中, 产生正效应的等位基因所联系的标记积累和/或产生负面效应的等位基因的标记消除为基础的。

分子标记也可用在定性性状选育进程中。例如，在回交育种计划中, 与等位基因密切相关的标记或者标记内含有实际相关的等位基因序列的分子标记，可用于选择含有感兴趣的等位基因的植株。分子标记也可以用来选择轮回亲本的基因组和避免选择供体亲本的基因组。使用此程序, 可以减少留在被选植株中供体亲本基因组的数量。它也可以用来减少轮回亲本回交方案所需的回交的数目。分子标记在遴选过程中的使用通常被称为遗传标记提高甄选。

在育种中, 生产双单倍体也可用于玉米自交系的研发。双单倍体是由杂合体加倍一组染色体（1N），产生一种完全同合的个体。比如，见万等人的“通过秋水仙素处理源于花药的玉米愈伤组织来提高双单倍体植株的有效产量”，理论与应用遗传，77:889-892，1989。这可能是有利的，因为这个过程省略了通过由杂合子源的多代的自交来得到一个纯合植株。

• 【合作】玉米种子 PH4CV专利翻译合作

“适合地区”一词用于指代其环境条件非常适合该玉米系（PH4CV）的地区。它基于许多因素，例如：成熟所需的天数、抗虫性、抗病性、以及抗旱性。“适合地区”并不意味着该玉米系在适合地区的每一个地方都能生长，也不意味着该玉米系不能在适合地区之外生长。

中部玉米种植地带：爱荷华，伊利诺伊，印第安纳

干燥地带：北达科达，南达科达，内布拉斯加，堪萨斯，科罗拉多，以及俄克拉荷马等州的非灌溉地区。

美国东部地区：俄亥俄，宾夕法尼亚，特拉华尔，马里兰，弗吉尼亚，以及西弗吉尼亚。

美国中北部地区：明尼苏达和威斯康星。

美加东北部地区：密歇根，纽约，佛蒙特，以及加拿大的安大略和魁北克。

美国西北部：北达科达，南达科达，怀俄明，华盛顿，俄勒冈，蒙塔那，犹他，以及爱达荷。

美国中南部：密苏里，田纳西，肯塔基，以及阿肯色。

美国东南部：北卡罗来纳，南卡罗来纳，乔治亚，佛罗里达，阿拉巴马，密西西比，以及路易斯安娜。

美国西南部：得克萨斯，俄克拉荷马，新墨西哥，以及亚利桑那

美国西部：内布拉斯加，堪萨斯，科罗拉多，以及加里福利亚。

欧洲濒海地区：法国，德国，比利时，和奥地利。

• 【合作】玉米种子 PH4CV专利翻译合作