If so please describe and what are it's origins...
Chocolate Thai?
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If so please describe and what are it's origins...
Chocolate Thai?
Hey there J ,
CC comes from THseeds. Here's the info about it on their site...
This is real candy ! With a definitive Kush bottom this pure Indica will melt in your mouth and stick to your hands. Thick, deep- green leaves and fat dense buds will make every trip to the grow room feel like you are , "a kid in a candy store." Chocolate Chunk is quite easy to grow due to it's quick flowering time and "single cola" growth pattern. Works great with the Sea of Green Method
Type : pure Indica
Height : 100-125 cm
Yield : 350-400 p.s.m.
Flowering Time : 55-60 days
laters
KK
What is in sweet tooth? K.K.
No I dont think swt is in it , swt = spg (clone only) x bb
From the write up it looks like it is a full indy with a heavy kush influence.
read it again
Hey there J ,
Kushy was right about what swt is , I think he just misread your question.
Sweet Tooth is from Breeder Steve at Spice Of Life seeds.
Swt = Sweet Pink Grapefruit x Blueberry Male
Swt#1 = Sweet Pink Grapefruit x Blueberry Male , Backcrossed to Sweet Pink Grapefruit mother (1st time)
Swt#2 = Sweet Pink Grapefruit x Blueberry Male , Backcrossed to Sweet Pink Grapefruit mother (2nd time)
Swt#3 = Sweet Pink Grapefruit x Blueberry Male , Backcrossed to Sweet Pink Grapefruit mother (3rd time)
So which one is the Swt that is in the mortarebel strains...
I wonder what kushy ment.
Could you please explain what the F3 means on the apollo 11?
Hey J ,
Swt#3 was used in all of the newest projects...
When you cross two different IBL strains for the FIRST time, it is called the F1 generation. When you cross two of the same F1 hybrid (inbreed), it is called the F2 generation , etc.., etc..
laters
KK
oh, I think kushy thought you were asking If swt was in c.chunk.
Ya I think so... thanks for the explination.
So F3 is more stable than F2 or F1 because of the inbreeding?
Here's some articles that may help ... Have fun :)
What really is an F1 cross?
Well defining the terms P1, F1, F2, homozygous, and heterogygous can be a simple task, however, applying them to applied genetics can often create confusion. Depending on your point of reference, a plant could be described as any of these terms. For our specific field of interest it's important to further define these terms to reduce confusion and protect the consumers. First I'll provide the classic scientific definition of these and other related terms and then I'll dive into each term into detail.
Heterzygous - a condition when two genes for a trait are not the same on each member of a pair of homologous chromosomes; individuals heterozygous for a trait are indicated by an "Aa" or "aA" notation and are not true breeding for that trait.(Clarke)
Homozygous - the condition existing when the genes for a trait are the same on both chromosomes of a homologous pair; individuals homozygous for a trait are indicated by "AA" or "aa" and are true breeding for that trait. (Clarke)
- Now the heterozygous and homozygous terms can be applied to one trait or a group of traits within an individual or a group of individuals. Depending on your point of reference, an individual or group can be
considered both homozygous or heterozygous. For instance, say you have two individuals that are both short (S) and have webbed leaves (W) and have the following genotypes.
#1 = SSWW
#2 = SSWw
They are both homozygous for the short trait but only individual #1 is homozygous for the webbed leaf trait. Individual #2 is heterozygous for the webbed leaf trait and would be considered a heterozygous individual. As a goup, they would be considered heterozygous in general by some and homozygous by others. It would depend on your point of reference and the overall importance you place on the webbed leaf trait. Most would consider it to be heterozygous.
For example, the blueberry cannabis strain is considered a true breeding homozygous seed line because as a whole the many offspring have a similar look and produce a similar product. However there are often subtle differences between the plants of characters such as stem colour and potency. When taking a close look at blueberry, you will find heterozygous traits, but because of the whole overall look, we still generally consider them homozygous for the purpose of breeding programs. Using dogs is another way to explain this, take a dobie for example, you cant tell the difference between dobies, but you can tell a dobie from another breed. Ya follow?
Hybrid - An individual produced by crossing two parents of different genotypes. Clarke says that a hybrid is a heterozygous individual resulting from crossing two seperate strains.
- For the purpose of seedbanks, a hybrid is in general, a cross between any two unrelated seedlines. ANY HYBRID IS heterozygous and NOT TRUE BREEDING.
F1 hybrid - is the first generation of a cross between any two unrelated seedlines in the creation of a hybrid. F1 hybrids can be uniform or variable depending on the P1 parent stock used.
F2 hybrid - is the offspring of a cross between two F1 plants (Clarke). What Clarke and other sources don't make clear is do the two F1's need to be from the same parents? By convention they don't. As well, german geneticists often describe a backcross of an F1 back to a P1 parent as a F2 cross.
- OK lets say we take blueberry and cross it with romulan (both relatively true breeding of their unique traits) to create the F1 hybrid romberry. Now lets cross the F1 romberry with a NL/Haze F1 hybrid. (Ed.note:The textbooks consider this a 'double cross'.)
Some could say this is a F1 cross of romberry and NL/Haze. Others could argue that it is a F2 cross of two F1 hybrids. Gets confusing doesn't it? Now lets cross this Romberry/NL/Haze(RNH) with a Skunk#1/NL#5 F1 hybrid to create RNHSN. Now some would argue that RNHSN is an F1 hybrid between RNH and SK/NL seedlines. Others would call it an F2.
- So what does this mean to the consumer? It means that a seed bank can call a cross whatever it wants until the industry adopts some standards. This is what this article will attempt to initiate. Clarke eludes to
standardising these definitions but never really gets around to it. Fortunately other plant breeding communities have (Colangelli, Grossnickle&Russell, Watts, &Wright) and adopting their standards
makes the most sense and offers the best protection to the seedbank consumer.
Watts defines an F1 as the heterozygous offspring between two homozygous but unrelated seedlines. This makes sense and gives the F1 generation a unique combination of traits; uniform phenotype but not true breeding. This is important in the plant breeding world. This means that when a customer buys F1 seeds that they should expect uniform results. It also means that the breeder's work is protected from being duplicated by any other means than using the original P1 (true breeding parents). [There are
exceptions to this by using techniques such as repeated backcrosses (cubing the clone).
F2 crosses are the offspring of crossing two F1 hybrids. This means that they will not be uniform nor will they breed true. However, F3, F4, F5, etc will also share these characteristics, so to simplify terminology for the seedbanks and seedbank merchants, they can all be classified as F2 seeds in general.
What does this mean for the preceeding example? Well, the blueberry, romulan, skunk#1, NL#5, and haze were all P1 true breeding seedlines or strains (another term that needs clarification). Romberry, NL/Haze, and SK/NL were all F1 hybrids. Both the Romberry/NL/Haze and the RNHSN would be F2s. Within each group the consumer can know what to expect for the price they are paying.
Few cannabis seedbanks (if any) and their breeders are following these definitions and are subsequently creating confusion within the cannabis seedbuying community. This is a change that needs to happen.
Note: this is a rough draft to be published to the internet. Hopefully in time it or something similar will be used to help establish an industry standard. Any comments and critism is welcome to aid in the production of the final draft. Small steps like this can only benefit the cannabis community over the long haul.
REFERENCES:
Clarke RC. 1981. Marijuana Botony Ronin Publishing, California
Colangeli AM. 1989. Advanced Biology notes. University of Victoria, BC
Futuyma DJ. 1986. Evolutionary Biology Sinauer Associates, Inc. Massachusetts
Klug & Cummings. 1986. Concepts of Genetics 2nd ed. Scott, Foresman, & comp. Illinois
Grossnickle & Russell. 1989. Stock quality improvement of yellow-cedar. Canada-BC Forest Resources Developement Agreement (F.R.D.A.) Project 2.40
Watts. 1980. Flower & Vegetable Plant Breeding Grower Books, London
Wright JW Introduction to Forest Genetics Academic Press, San Francisco
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Factor : A particle or unit in the organism which is responsible for the inheritance and expression of a particular character.
Gene : Mendel??s factor is now known as gene. A gene is a particular segment of a DNA molecule which determines the inheritance and expression of a particular character.
Alleles or Allelomorphs : Two or more alternative forms of a gene are called alleles or allelomorphs. For example in pea, the gene for producing seed shape may occur in two alternative forms: round (R) and wrinkled (r). Round and wrinkled forms of the gene are alleles of each other. Alleles occupy same locus on homologous chromosomes.
Dominant : Of the two alternating forms (allomorphs) of a trait, the one which appears in the F1 hybrid is called the dominant trait (Dominant Allele).
Recessive : Of the two alternating allomorphs of a trait, one which is suppressed (does not appear) in the F1 hybrid is called the recessive trait (recessive allele).
Genotype : The genetic make-up or genic constitution of an individual (which he/she inherits from the parents ) is called the genotype, e.g., the genotype of pure round seeded parent will be RR.
Phenotype : The external (morphological) appearance of an individual for any trait or traits is called the phenotype, e.g. for seeds, round shape or wrinkled shape is the phenotype.
Homozygous : An individual possessing (receiving from parents) identical alleles for a trait is said to be homozygous or pure for that trait, e.g. plant with RR alleles is homozygous for the seed shape. A homozygous always breeds true for that trait.
Heterozygous : An individual receiving dissimilar alleles for a trait is said to be heterozygous or impure for that trait, e.g. a plant with Rr alleles is heterozygous for the seed shape. Heterozygous is also called a hybrid.
Parent generations : The parents used for the first cross represent the parent (or P1) generation.
F1 generation : The progeny produced from a cross between two parents (P1) is called First Filial or F1 generation.
Inbreeding : When the individuals of a progeny (e.g. F1 generation) are allowed to cross with each other, it is called inbreeding.
F2 generation : The progeny resulting from self hybridization or inbreeding of F1 individuals is called Second Filial or F2 generation.
Monohybrid cross : The cross between two parents differing in a single pair of contrasting characters is called monohybrid cross and the F1offspring as the hybrid(heterozygous for one trait only).
Monohybrid ratio : The phenotypic ratio of 3 dominants : 1 recessive obtained in the F2 generation from the monohybrid cross is called monohybrid ratio.
Dihybrid cross : The cross between two parents in which two pairs of contrasting characters are studied simultaneously for the inheritance pattern. The F1 offspring is described as dihybrid or double heterozygous (i.e. with dissimilar alleles for two characters).
Dihybrid ratio : The phenotypic ratio obtained in the F2 generation from a dihybrid cross is called dihybrid ratio. In Mendelian experiments, this ratio is 9:3:3:1.
Homologues or Homologous chromosomes : The morphologically similar looking chromosomes in a diploid cell (one chromosome coming from the male parent and the other from the female parent) are called homologous chromosomes. They have identical gene loci bearing alleles.
DNA:
Deoxyribonucleic acid, the heritable material of an organism.
Gene:
The units of inheritance that transmit information from parents to offspring.
Chromosome: A long threadlike association of genes in the nucleus of all eukaryotic cells which are visible during meiosis and mitosis. A chromosome consists out of DNA and proteins. An organism always has 2n chromosomes, which means that all chromosomes are paired.
Genotype: This is the genetic makeup of an organism: the genes
Phenotype: The physical and physiological traits of an organism. These are influenced by genetic makeup (genes) and surrounding.
Allele:
Another word for gene. Each chromosome has a copy of this allel, thus a gene-pair.
Homozygous:
This term indicates that an organism has two identical alleles at a single place on a chromosome. This results in an organism that breeds true for only one trait.
Heterozygous: This term indicates that an organism has two different copies of a gene on each chromosome.
Dominant gene: In a heterozygote, this allele (gene) is fully expressed in the phenotype. In genetic schemes, these genes are always depicted with a capital letter.
Recessive gene: In a heterozygote, this allele (gene) is completely masked in the phenotype. In genetic schemes, these genes are always depicted with a lower case letter.
Intermediair gene: This is when in a heterozygote, an allele (gene) is not fully masked in the phenotype. You can already see some of the characteristics of the gene.
Good examples of this are the genes for crown- and doubletail.
- Fish with only one copy of the crowntail (ct) gene (will most of the time) already show some ray extensions.
- Fish with only one copy of the doubletail (dt) gene (will most of the time) already show a broader dorsal fin and fuller finnage.
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How to indicate the different generations?
When two unrelated parents (P) are crossed their hybrid offspring is called the F1 generation (for the first filial generation).
When the F1 generation is interbred their offspring is called the F2 generation (for the second filial generation).
When the F2 generation is interbred their offspring is called the F3 generation (for the third filial generation).
And so on........
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Now try to visualize this using for example the allele for hair color in humans:
Brown hair is a dominant trait. How is it possible that two parents with brown hair get a blond daughter of son?
The allel for ??brown hair? is dominant and depicted with ??B?.
The allel for ??blond hair? is recessive and depicted with ??b?.
The answer lies here: Remember that all alleles come in pairs and that the parents have to be heterozygous for the allel for haircolor. This means that both parents have to posses the recessive trait for blond hair (??b?) besides the dominant trait for brown hair (??B?), thus ??Bb?. The best thing to visualize this is by the use of a Punnet-square:
Summary:
The offspring of two parents carrying the heterozygous ??Bb? genotype can result in the following offspring: 25% homozygous for brown hair (??BB?), 50% heterozygous for brown hair (??Bb?) and 25% homozygous for blond hair (??bb?).
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Inbreeding, linebreeding and outcrossing
In order to breed good quality Betta splendens, different breeding methods are used. Inbreeding, linebreeding and outcrossing play an important role in setting up a quality line of Betta splendens.
Inbreeding:
A systematic program of breeding closely-related animals. This generally refers to father x daughter, mother x son, and brother x sister parings.
Linebreeding:
This term is used to describe a less intense program of inbreeding. This generally refers to closely related pairings like uncle x niece and halfbrother x halfsister.
Outcrossing: Outcrossing refers to the breeding of two unrelated (inbred) strains.
What does inbreeding do in the genetic sense?
Inbreeding will increase the probability that any given gene has two identical copies derived from the same ancestor. It tends to make all genes more homozygous. Remember each animal has 2 two copies of a given gene (technically speaking, two alleles at each locus on the chromosome) one from each parent. Unfortunately we are not able to only select the desired genes we want because genes come as a package??.
One has to keep in mind that in the quest for fixating the desired traits by inbreeding, there is always the chance that we unintentionally loose some of the desired (??good?) genes and fixate some undesired (??bad?) genes which surface throughout the process.
Good examples of this are for instance the inbred strains of laboratory rodents. The process of inbreeding used to create this type of strains most of the time kills the majority of the strains between the 8th and 12th generations due to a loss of fertility (reduction in litter size) and viability. The strains, which survive these critical 8th-12th generations, form the inbred laboratory strains. These animals are homozygous for a more or less random selection of genes derived form the initial pair.
Why outcrossing?
As described in the example of the laboratory rodents above, in general inbreeding can be done up to F8 (8th generation). Most times the rate of breeding success is really low at this stage.
When we extrapolate this example to Betta splendens, extensive inbreeding can result in fish which show a number of undesired characteristics like: smaller bodies, decrease viability, decrease of aggressiveness, decrease of fertility, not building bubble nests, fish which don??t know how to wrap themselves around the female, etc. This is why it is advisable to use an out-cross (unrelated partner, fresh blood) once in a while in order to keep the lines healthy and viable.
When choosing the outcross candidate, the breeder always needs to decide which outcross candidate possesses the desired traits that can improve the established inbred line. Off course there is also a risk in outcrossing because a breeder can loose the type of betta he has been worked on for a long time. Breeders often decide to cross the hybrid offspring of an outcross back to their original inbred line. This in order to add the new or improven traits that were brought in by using an outcross, but also in order to eliminate possible bad traits brought by the outcross.
Terminology & Definitions II
Population Genetics Definitions
Adaptation = A trait that increases the survivability of an individual or its ability to reproduce when compared to individuals that do not possess that trait
Adaptive Radiation = Radiation of a group of organisms into populations adapted to exploit different ecological niches
Adaptive Trait = A trait that increases the fitness of an individual
Allopatric Speciation = Speciation that occurs when populations become geographically isolated due to genetic drift and when selection pressures differ between the two populations
Assortative Mating = A mating pattern that occurs when individuals tend to mate with other individuals of the same genotype and phenotype
Bottleneck = A large scale but short term decrease in the population size followed by an increase in the population size. Can cause speciation events
Convergent Evolution = Similarities between species that are the result of similar, but evolutionarily independent responses to common environmental factors. E.g. The wing of a bird and the wing of a butterfly
Evolution = Descent with modification = a change in the characteristics of a population over time = changes in the allele frequency of a population over time
Fitness = The degree to which an individual contributes genes to the next generation
Founder Effect = The establishment of a new population by a small number of individuals. can cause speciation events
Frequency = The proportion of a genotype, phenotype, gamete, or allele in a population. E.g. 6/10 have brown hair = a frequency of 0.6
Gene Pool = All of the copies of all of the alleles in a population that could be contributed by members of the present generation to members of the next generation
Genetic Drift = A change in the allele frequency of a population resulting from sampling error in taking gametes from the gene pool to make zygotes and from chance variation in the survival/reproductive success of individuals
Hardy-Weinberg Equilibrium = An ideal population in which the allele and genotype frequencies do not change from one generation to the next generation due to a lack of selection, mutation, migration, and genetic drift and due to the occurrence of random mating
Heritability = The fraction of the total phenotypic variation in a population that is caused by genetic differences between individuals
Homology = Similarities between species that results from the inheritance of traits from a common ancestor
Homoplasy = Similarities in the traits found in different species that is due to convergent evolution, parallelism, or reversal. It is not due to common descent
Hybrid Zone = A geographic zone where different populations/species interbreed
Inbreeding = Mating between relatives
Inbreeding Depression = A decrease in the fitness of an individual or a population due to inbreeding. It is often the result of a decrease in heterozygosity of an increase in the homozygosity (both are due to inbreeding)
Inclusive Fitness = An individual's total fitness = indirect fitness (fitness due to the reproduction by relatives made possible by that individual) + direct fitness (fitness due to the individual's own reproduction)
Macroevolution = Large scale evolutionary change = evolution of the differences between populations that would justify their placement into different genera (or higher level taxa)
Microevolution = Changes in the gene frequencies and trait distributions that occur within species and populations
Migration = The movement of alleles from one population to another population due to the movement of individuals or gametes
Natural Selection = Specific phenotypes confer increased survivability or reproductive success to the individuals that possess them
Negative Selection = Selection against deleterious mutations
Outbreeding = Mating between unrelated individuals
Polymorphism = The existence of more than one allele or variant in a population
Population = A group of individuals capable of interbreeding plus all of their offspring
Positive Selection = Selection for advantageous mutations
Preadaptation = A trait that changes due to natural selection and takes on a new function
Relative Fitness = The fitness of an individual, phenotype, or genotype compared to other individuals in the population
Species = Groups of populations that are capable of interbreeding and are evolutionarily independent from other populations
Sympatric Speciation = A speciation event involving species living in the same geographic area
Synapomorphy = A shared derived trait
Transitional Form = A species exhibiting traits that are common to both the ancestral and derived groups
Phylogenetics Definitions
Bootstrapping = A term commonly used in phylogenetic reconstruction = A technique used for estimating the strength of evidence for the existence of a particular node in a phylogenetic tree. Values range between 0% and 100% with 100% being the strongest level of support
Branch = A branch in a phylogenetic tree. See diagram
Clade = A group of species descended from a common ancestor = a monophyletic group
Evolution = Descent with modification = a change in the characteristics of a population over time = changes in the allele frequency of a population over time
Extant = Living today
Extinct = Not living today
Monophyletic Group = A population of a group of species descended from a common ancestor
Node = Branching point in a phylogenetic tree. See diagram
Outgroup = In phylogenetic analysis, a group that diverged prior to the rest of the taxa
Paraphyletic Group = A group of species that includes the common ancestor and some, but not all of that common ancestor's descendants
Phylogeny = The evolutionary history of a group
Psuedogene = DNA sequences that are homologous and resemble functioning genes, but are not transcribed
Sister Species = Species that diverged from the same node on a phylogenetic tree
Species = Groups of populations that are capable of interbreeding and are evolutionarily independent from other populations
Taxon = Any named group of organisms
Tip = The end of a branch on a phylogenetic tree.
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Symbolism for describing populations, lines, and individuals
[Chapter 3 in Fehr, (1987)]
Two symbols are widely used to describe populations and lines derived from them. The first, F, described filial (offspring) generations after a cross between two parents. It is the more versatile of the symbols, because it can denote populations derived by either self pollination or by random mating. The second symbol, S, designates generations of self fertilization. Breeders often attach different generations to particular symbols, so clear indications of how the symbols are being used is imperative.
The F symbol
F1 generation: The first generation following a cross is denoted as the F1 generation. This cross is also known as a single cross, and the progeny as a single cross hybrid. Typically, the parents used in a cross are inbred (pure) lines, making each of them homozygous at (virtually) every locus throughout the genome. Thus, the progeny derived from this cross will be identical (barring a mutation) and heterozygous at all loci for which allelic differences existed between the parents. However, if the parents are not inbred, they will be heterozygous at some loci. Therefore, the F1 progeny will not all be identical; each F1 will have a different genotype. Some examples of this type of cross include a cross between two hybrids (also known as a double cross) or a cross between two highly heterozygous genotypes. However, some scientists refer to this situation as an F2, thereby causing much confusion (see below).
F2 generation: Typically, an F1 hybrid is self fertilized to produce a segregating population in which selection (or genetic analysis) is conducted. In the common case of an inbred line cross, the F2 will segregate for single genes at which the parents carry distinct alleles in the well-known genetic ratios of 3:1 or 1:2:1, depending on the dominance relationships between the alleles. [See Figure 3-2 in Fehr (1987).] The F2 can also refer to a base population formed by multiple generations of random mating. Finally, as mentioned above, the F2 can also refer to the progeny of a cross between heterozygous parents. Fehr (1987) uses this terminology.
F3 and succeeding generations: Generally, F3, F4, etc. refer to the population formed by successive generations of self-pollination after the F2. The genotypic array of the population varies considerably depending on selection, genetic constitution of the F2, and the size of the population. Small population sizes are subject to genetic drift. [See Figure 3-2 in Fehr (1987) for the case of a large population without selection.] In contrast, F3, F4, ... could refer to a population undergoing successive rounds of random mating without selection. This situation is sometimes denoted using Syn 1, for Synthetic 1, to represent the population formed by random mating the F2 and Syn 2, Syn 3, etc. signifying successive rounds of random mating. Further discussion of synthetics is reserved for later.
The S symbol
The S symbol can be used in two ways. In the most common, which we will adopt in this class, S0 = F2. Alternatively, some breeders use S0 = F1. In either case, succeeding generations follow in a like manner, e.g. S1 = F3 (in our system), etc.
Using F and S to describe inbred lines
Two systems have been developed by breeders to designate inbred lines using the F or S symbols. System I simply describes the generation of the line being grown. While this provides some information to the breeders, a better system, which we??ll call System II, also describes the generation of the plant from which the line originated. This more complete information allows an easier calculation of expected genetic variation than that provided by system I. We will use System II will be used in this class.
The general format of a line designation in System I is Fx, where ??x? designates the generation of the line being grown. In System II, the general format is Fy:x, where ??x? designates the generation of the line being grown and ??y? designates the generation from which that line derived. Some examples will help clarify the nomenclature.
Assume a single F2 (S0) plant is selected and its seeds, which are the F3 (S1) generation, are planted the next season. Under System I, this line would be referred to as an F3 line (S1 line). Under System II, it would be termed an F2:3 line (S0:1 line), which is spoken as ??an F2-derived line in F3.?
If all F3 plants in the line are harvested in bulk??that is, all the F4 seeds from each F3 plant in the line are pooled together??and some of the F4 seeds are planted in the next year, then the line growing in the field is called an F4 line (S2 line) in System I and an F2:4 line (S0:2 line) in System II.
If instead, a single F3 plant had been selected, and its F4 seeds harvested and planted the next season, the line would be still be termed an F4 line (S2 line) under System I, but the different means of harvesting would be captured in System II by designating the line as an F3:4 line (S1:2 line).
In determining which generation a particular line derived from, realize that we are attempting to give an idea of how much genetic variation exists within that line. When all plants from a line are bulked for the next generation, then all the variation within the original line remains next season. In contrast, when only a single plant is selected for advancement, then the variation in the original line is now truncated to that present in that single plant. Thus the line in the next season will have less genetic variation than the line in the previous generation.
here's a definition of population from the same coursework . . .
Populations
Genetically speaking, a population is a group of individuals sharing a common gene pool. If all individuals within the population have the same genotype, the population is homogeneous; if the individuals have distinct genotypes, the population is heterogenous.
The genetic constitution of populations and individuals within the populations varies depending on the reproductive system of a species. A natural population of a cross-pollinated plant species consists of a heterogenous mixture of individuals, some of which will be heterozygous at particular loci. In contrast, a natural population of a self-pollinated species will also consist of a heterogenous mixture (most likely) of individuals, but each individual will be homozygous at most loci within its genome. Populations of an asexually reproducing species may be homogeneous or heterogeneous; individuals will likely be heterozygous at many loci.
Some examples of populations familiar to agronomists are (1) a commercial maize hybrid cultivar, which is homogeneous and heterozygous, (2) a commercial soybean pure line cultivar, which is homogeneous and homozygous,(3) a commercial alfalfa synthetic cultivar, which is heterogeneous and heterozygous, and (4) a commercial potato cultivar, which is homogeneous but individuals are heterozygous.
Natural selection can work on this variation to result in different genetic profiles of the populations over time. As an example, see Table 13-1 in Allard (1960), in which a number of barley varieties were composited equally, grown in field plots, bulk harvested, and replanted over a series of years and locations. The resulting populations are considerably different from the initial frequencies
Types of cultivars
The cultivars that will be developed from a breeding programs can be divided into four types: pure lines, hybrids, synthetics, and clonal cultivars. Although further information on these is given later, a brief synopsis follows. Pure line cultivars consist of one genotype, homozygous at all loci. Most small grain species??oat, wheat, barley??and soybean are examples of crops for which the commercial product is a pure line cultivar. A variation on the pure line cultivar is a multiline, in which multiple pure lines are composited together. Multilines are often used in an effort to stabilize production resulting from disease/pest pressures and/or heterogeneous growing environments.
Typically, hybrids are formed by crossing two inbred lines to form a single cross hybrid. Crossing a single cross hybrid to a third inbred line is called a three-way hybrid, and crossing two single cross hybrids results in a double cross hybrid. In the case of a single cross, the hybrid consists of one genotype, heterozygous at many (but probably not all) loci. Maize and many vegetables are typically sold as hybrid cultivars. Note that hybrids can also be formed by crossing populations, which are termed ??population hybrids? or ??semi-hybrids.?
Synthetic cultivars are populations derived by intercrossing a selected set of parental genotypes followed by two to three generations of open pollination prior to release to the farmer. Thus, a synthetic cultivar is a complex mix of genotypes, each one distinct, and each of which will be heterozygous at some loci. Alfalfa and many other forage grasses and legumes are usually sold as hybrid cultivars.
Clonal cultivars are produced by tubers, stolons, rhizomes, stem cuttings, etc., such that each individual is identical, but heterozygous at multiple loci. Potato, sugarcane, bermudagrass, many fruit trees, and many other species are sold as clonal cultivars. Cultivars of apomictic species are distributed as seeds, but all are identical to the parent plant.
Regardless of the type of cultivars to be released, the development of some type of population from which desirable individuals can be selected to produce the cultivar is likely a requirement for breeding most crops.
all of these excerpts are from the actual class notes provided by the professor . . . here's some more from Principles of Cultivar Development . . .
Parental selection
Selecting the parents to develop a population is the essential component of both nascent and mature plant breeding programs. But how to do it? Many questions arise. What are the primary traits of interest? What secondary traits need to be considered? What is their inheritance? Who is the beneficiary of the cultivars to come from the population??farmers, consumers, seed companies? What are the biggest issues facing a crop??diseases, pests, nutritional profiles, etc.? Should the needs of the cropping system be included, not just the needs of the crop per se? No clear answer can be given to these questions, but the breeder must take some note of each of them as he or she assembles the parents to be used to form their population.
After answering the questions regarding needs and desired end products, the breeder attempts to identify germplasm that contains the traits and variability for the traits that are needed. Two factors are important in developing a base population: (1) the mean performance of the population??that is, the base population should have a reasonable mean performance at the outset of the breeding program, and (2) the genetic variance of the population??that is, a population with a high mean performance will not be useful for future selection if it has no genetic variability.
Thus, parents should be selected that have good performance but that derive from a variety of ancestries to optimize both mean performance and genetic variance in the population. Once the parents have been intercrossed in some manner (as discussed below), selection can begin. Typically, breeders make good x good crosses to capitalize on the improvement made up until now and to push it further. The hope is that recombination among the elite parental genotypes will produce transgressive progeny, thereby advancing the population, and the resulting cultivars, to a new level.
The sources of germplasm can be virtually anything that crosses with your crop, but in general, the best material availabe??commercial cultivars or elite breeding lines??is a good starting point. A problem arises if the variation for the trait of interest is small among these sources. In this case, acceptable breeding lines, superior in one or more characteristics but deficient in others, is a good choice. If more variation is needed, or if new traits need to be incorporated (e.g., resistance to a new disease), plant introductions can be considered
Well when you want more to read just holla :D
KK
Wow ...Did that answer my question or what...
So what I gathered is that the main differance between F1 and F2,F3 is the F2,F3 is less stable in the sence that you probably will get differant pheno's which might not be all bad if you find 1 you like.
My 2 somango's are 2 pheno's...1 Jack Herer and 1 super skunk(maybe big skunk korian)
I think the skunk pheno is the popular one but Jack Herer is a great strain so we'll see when I do a harvest report.
thats right J , when you cross two true ibl parents you will get a F1 , when you cross two f1's you get f2's which will produce plants with a more wider range of phenos and may even through out a rare super pheno female :D
Growing F2's and S1's (selfed seeds) are the best way to dive into the gene pool of a strain and really get to check it out.
laters
KK :)
Cool,thanks man...I'm thinking of starting my own breeding set up eventually ,so I'm studying up alot way before I ever get started.