主题：【合作】玉米种子 PH4CV专利翻译合作 -- 急风劲草

发明进一步的具体表征（Further Embodiments of the Invention ）

Further Embodiments of the Invention

This invention also is directed to methods for producing a maize plant by crossing a first parent maize plant with a second parent maize plant wherein either the first or second parent maize plant is an inbred maize plant of the line PH4CV. Further, both first and second parent maize plants can come from the inbred maize line PH4CV. Still further, this invention also is directed to methods for producing an inbred maize line PH4CV-derived maize plant by crossing inbred maize line PH4CV with a second maize plant and growing the progeny seed, and repeating the crossing and growing steps with the inbred maize line PH4CV-derived plant from 1 to 2 times, 1 to 3 times 1 to 4 times, or 1 to 5 times. Thus, any such methods using the inbred maize line PH4CV are part of this invention: selfing, sibbing, backcrosses, hybrid production, crosses to populations, and the like. All plants produced using inbred maize line PH4CV as a parent are within the scope of this invention, including plants derived from inbred maize line PH4CV. This includes varieties essentially derived from variety PH4CV with the term “essentially derived variety” having the meaning ascribed to such term in 7 U.S.C. § 2104(a)(3) of the Plant Variety Protection Act, which definition is hereby incorporated by reference. This also includes progeny plants and parts thereof with at least one ancestor that is PH4CV, and more specifically, where the pedigree of the progeny includes 1, 2, 3, 4, and/or 5 or less cross-pollinations to a maize plant other than PH4CV or a plant that has PH4CV as a progenitor. All breeders of ordinary skill in the art maintain pedigree records of their breeding programs. These pedigree records contain a detailed description of the breeding process, including a listing of all parental lines used in the breeding process and information on how such line was used. Thus, a breeder would know if PH4CV were used in the development of a progeny line, and would also know how many crosses to a line other than PH4CV or line with PH4CV as a progenitor were made in the development of any progeny line. The inbred maize line may also be used in crosses with other, different, maize inbreds to produce first generation (F 1 ) maize hybrid seeds and plants with superior characteristics.

Specific methods and products produced using inbred line PH4CV in plant breeding are encompassed within the scope of the invention listed above.

One such embodiment is a method for developing a PH4CV progeny maize plant in a maize plant breeding program comprising: obtaining PH4CV or its parts, utilizing said plant or plant parts as a source of breeding material; and selecting a PH4CV progeny plant with molecular markers in common with PH4CV or morphological and/or physiological characteristics selected from the characteristics listed in Tables 1 or 2. Breeding steps that may be used in the maize plant breeding program include pedigree breeding, backcrossing, mutation breeding, and recurrent selection. In conjunction with these steps, techniques such as restriction fragment polymorphism enhanced selection, genetic marker enhanced selection (for example SSR markers), and the making of double haploids may be utilized.

Another such embodiment is the method of crossing inbred maize line PH4CV with another maize plant, such as a different maize inbred line, to form a first generation population of F1 hybrid plants. The population of first generation F1 hybrid plants produced by this method is also an embodiment of the invention. This first generation population of F1 plants will comprise an essentially complete set of the alleles of inbred line PH4CV. One of ordinary skill in the art can utilize either breeder books or molecular methods to identify a particular F1 hybrid plant produced using inbred line PH4CV, and any such individual plant is also encompassed by this invention. These embodiments also cover use of these methods with transgenic or single gene conversions of inbred line PH4CV.

Another such embodiment of this invention is a method of using inbred line PH4CV in breeding that involves the repeated backcrossing to inbred line PH4CV any number of times. Using backcrossing methods, or even the tissue culture and transgenic methods described herein, the single gene conversion methods described herein, or other breeding methods known to one of ordinary skill in the art, one can develop individual plants, plant cells, and populations of plants that retain at least 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 79%, 80%, 81%. 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 99.5% genetic contribution from inbred line PH4CV. The percentage of the genetics retained in the progeny may be measured by either pedigree analysis or through the use of genetic techniques such as molecular markers or electrophoresis. In pedigree analysis, on average 50% of the starting germplasm would be passed to the progeny line after one cross to another line, 25% after another cross to a different line, and so on. Molecular markers could also be used to confirm and/or determine the pedigree of the progeny line.

One method for producing a line derived from inbred line PH4CV is as follows. One of ordinary skill in the art would obtain a seed from the cross between inbred line PH4CV and another variety of maize, such as an elite inbred variety. The F1 seed derived from this cross would be grown to form a homogeneous population. The F1 seed would contain essentially all of the alleles from variety PH4CV and essentially all of the alleles from the other maize variety. The F1 nuclear genome would be made-up of 50% variety PH4CV and 50% of the other elite variety. The F1 seed would be grown and allowed to self, thereby forming F2 seed. On average the F2 seed would have derived 50% of its alleles from variety PH4CV and 50% from the other maize variety, but many individual plants from the population would have a greater percentage of their alleles derived from PH4CV (Wang J. and R. Bemardo, 2000, Crop Sci. 40:659-665 and Bemardo, R. and A. L. Kahler, 2001, Theor. Appl. Genet 102:986-992). The molecular markers of PH4CV could be used to select and retain those lines with high similarity to PH4CV. The F2 seed would be grown and selection of plants would be made based on visual observation, markers and/or measurement of traits. The traits used for selection may be any PH4CV trait described in this specification, including the inbred maize PH4CV traits of comparably good yield and comparably good tolerance to leaf blight, leaf spot and ear rot as mentioned herein. Such traits may also be the good general or specific combining ability of PH4CV, including its ability to produce hybrids with an approximate 113 CRM maturity, comparably high yield, comparably good foliar disease tolerance and comparably short ear and plant height. The PH4CV progeny plants that exhibit one or more of the desired PH4CV traits, such as those listed above would be selected and each plant would be harvested separately. This F3 seed from each plant would be grown in individual rows and allowed to self. Then selected rows or plants from the rows would be harvested individually. The selections would again be based on visual observation, markers and/or measurements for desirable traits of the plants, such as one or more of the desirable PH4CV traits listed above. The process of growing and selection would be repeated any number of times until a PH4CV progeny inbred plant is obtained. The PH4CV progeny inbred plant would contain desirable traits derived from inbred plant PH4CV, some of which may not have been expressed by the other maize variety to which inbred line PH4CV was crossed and some of which may have been expressed by both maize varieties but now would be at a level equal to or greater than the level expressed in inbred variety PH4CV. However, in each case the resulting progeny line would benefit from the efforts of the inventor(s), and would not have existed but for the inventor(s) work in creating PH4CV. The PH4CV progeny inbred plants would have, on average, 50% of their nuclear genes derived from inbred line PH4CV, but many individual plants from the population would have a greater percentage of their alleles derived from PH4CV. This breeding cycle, of crossing and selfing, and optional selection, may be repeated to produce another population of PH4CV progeny maize plants with, on average, 25% of their nuclear genes derived from inbred line PH4CV, but, again, many individual plants from the population would have a greater percentage of their alleles derived from PH4CV. Another embodiment of the invention is a PH4CV progeny plant that has received the desirable PH4CV traits listed above through the use of PH4CV, which traits were not exhibited by other plants used in the breeding process.

The previous example can be modified in numerous ways, for instance selection may or may not occur at every selfing generation, selection may occur before or after the actual self-pollination process occurs, or individual selections may be made by harvesting individual ears, plants, rows or plots at any point during the breeding process described. In addition, double haploid breeding methods may be used at any step in the process. The population of plants produced at each and any cycle of breeding is also an embodiment of the invention, and on average each such population would predictably consist of plants containing approximately 50% of its genes from inbred line PH4CV in the first breeding cycle, 25% of its genes from inbred line PH4CV in the second breeding cycle, 12.5% of its genes from inbred line PH4CV in the third breeding cycle and so on. However, in each case the use of PH4CV provides a substantial benefit. The linkage groups of PH4CV would be retained in the progeny lines, and since current estimates of the maize genome size is about 50,000-80,000 genes (Xiaowu, Gai et al., Nucleic Acids Research, 2000, Vol. 28, No. 1, 94-96), in addition to non-coding DNA that impacts gene expression, it provides a significant advantage to use PH4CV as starting material to produce a line that retains desired genetics or traits of PH4CV.

Another embodiment of this invention is the method of obtaining a substantially homozygous PH4CV progeny plant by obtaining a seed from the cross of PH4CV and another maize plant and applying double haploid methods to the F1 seed or F1 plant or to any successive filial generation. Such methods decrease the number of generations required to produce an inbred with similar genetics or characteristics to PH4CV. See Bernardo, R. and Kahler, A. L., Theor. Appl. Genet. 102:986-992, 2001.