Multicellular living organisms and unmodified parts thereof and – Plant – seedling – plant seed – or plant part – per se – Higher plant – seedling – plant seed – or plant part
Reexamination Certificate
2000-08-31
2003-09-16
McElwain, Elizabeth F. (Department: 1638)
Multicellular living organisms and unmodified parts thereof and
Plant, seedling, plant seed, or plant part, per se
Higher plant, seedling, plant seed, or plant part
C800S260000, C435S410000, C435S421000, C435S430000
Reexamination Certificate
active
06620989
ABSTRACT:
FIELD OF THE INVENTION
The invention is in the field of Brassica napus breeding (i.e., canola breeding), specifically relating to the inbred canola cultivar designated 46A41.
BACKGROUND OF THE INVENTION
The present invention relates to a new and distinctive rapeseed cultivar designated 46A41 which is the result of years of careful breeding and selection. Since such cultivar is of high quality and possesses a relatively low level of erucic acid in the vegetable oil component and a relatively low level of glucosinolate content in the meal component, it can be termed “canola” in accordance with the terminology commonly used by plant scientists.
The creation of new superior, agronomically sound, and stable high yielding cultivars of many plant types including canola has posed an ongoing challenge to plant breeders. In the practical application of a chosen breeding program, the breeder often initially selects and crosses two or more parental lines, followed by repeated selfing and selection, thereby producing many unique genetic combinations. The breeder can theoretically generate billions of different genetic combinations via crossing, selfing and mutagenesis. However, the breeder commonly has no direct control at the cellular level of the plant. Therefore, two breeders will never independently develop the same line, or even very similar lines, having the same canola traits.
Each year, the plant breeder selects the germplasm to advance to the next generation. This germplasm is grown under unique and different geographical, climatic and soil conditions, and further selections are then made during and at the end of the growing season. The characteristics of the cultivars which are developed are incapable of prediction in advance. This unpredictability is because the selection occurs in unique environments, with no control at the DNA level (using conventional breeding procedures), and with millions of different possible genetic combinations being generated. A breeder of ordinary skill cannot predict in advance the final resulting lines that are to be developed, except possibly in a very gross and general fashion. Even the same breeder is incapable of producing the same cultivar twice by using the same original parents and the same selection techniques. This unpredictability commonly results in the expenditure of large research monies and effort to develop a new and superior canola cultivar.
It is recognized that mass and recurrent selections can be used to improve populations of either self-or cross-pollinating crops. A genetically variable population of heterozygous individuals is either identified or created by intercrossing several different parents. The best plants are selected based on individual superiority, outstanding progeny, or excellent combining ability. The selected plants are intercrossed to produce a new population in which further cycles of selection are continued.
Backcross breeding has been used to transfer genes for a simply inherited, highly heritable trait into a desirable homozygous cultivar or inbred line that is the recurrent parent. The source of the trait to be transferred is called the donor parent. The resulting plant is expected to have the attributes of the recurrent parent (e.g., cultivar) and the desirable trait transferred from the donor parent. After the initial cross, individuals possessing the phenotype of the donor parent are selected and are repeatedly crossed (backcrossed) to the recurrent parent. The resulting plant is expected to have the attributes of the recurrent parent (e.g., cultivar) and the desirable trait transferred from the donor parent. This approach has been used extensively for breeding disease resistant cultivars of many plant types.
Each breeding program should include a periodic, objective evaluation of the efficiency of the breeding procedure. Evaluation criteria varies depending on the goal and objectives, but should include gain from selection per year based on comparisons to an appropriate standard, the overall value of the advanced breeding lines, and the number of successful cultivars produced per unit of input (e.g., per year, per dollar expended, etc.).
Various recurrent selection techniques are used to improve quantitatively inherited traits controlled by numerous genes. The use of recurrent selection in self-pollinating crops depends on the ease of pollination, the frequency of successful hybrids from each pollination, and the number of hybrid offspring from each successful cross.
Promising advanced breeding lines commonly are thoroughly tested and are compared to appropriate standards in environments representative of the commercial target area(s) for three or more years. The best lines are candidates for new commercial cultivars; and those still deficient in a few traits may be used as parents to produce new populations for further selection.
These processes, which lead to the final step of marketing and distribution, usually take from approximately eight to twelve years from the time the first cross is made. Therefore, the development of new cultivars such as that of the present invention is a time-consuming process that requires precise forward planning, efficient use of resources, and a minimum of changes in direction.
A most difficult task is the identification of individuals that are genetically superior, because for most traits the true genotypic value may be masked by other confounding plant traits or environmental factors. One method for identifying a superior plant is to observe its performance relative to other experimental plants and to one or more widely grown standard cultivars. If a single observation is inconclusive, replicated observations provide a better estimate of the genetic worth.
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.
The choice of breeding or selection methods depends on the mode of plant reproduction, the heritability of the trait(s) being improved, and the type of cultivar used commercially (e.g., F
1
hybrid cultivar, pureline cultivar, etc.). For highly heritable traits, a choice of superior individual plants evaluated at a single location will be effective, whereas for traits with low heritability, selection should be based on mean values obtained from replicated evaluations of families of related plants. Popular selection methods commonly include pedigree selection, modified pedigree selection, mass selection, and recurrent selection.
The complexity of inheritance influences the choice of the breeding method. Pedigree breeding and recurrent selection breeding methods are used to develop cultivars from breeding populations. 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 parents do not provide all of the desired characteristics, other sources can be included in the breeding population. In the pedigree method, superior plants are selfed and selected in successive generations. In the succeeding generations the heterozygous condition gives way to homogeneous lines as a result of self-pollination and selection. Typically in the pedigree method of breeding five or more generations of selfing and selection is practiced: F
1
→
F
2
; F
2
→
F
3
;
→
F
4
; F
4
→
F
5
,etc.
Pedigree breeding is commonly used for the improvement of largely self-pollinating crops such as canola. Two parents that are believed to possess favorable, complementary traits are crossed to produce an F
1
. An F
2
population is produced by selfing one or several F
1
's or by intercrossing two F
1
's (i.e., sib ma
Charne David G.
Patel Jayantilal D.
Thoonen Ferdinand G.
McElwain Elizabeth F.
Pioneer Hi-Bred International Inc.
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