Breeding techniques

I think we should separate the concepts of mendelian eugenics and the atrocities of ethnic / racial cleansing. The problem is of course that as science puts forward one basic concept, there will those who for idealogical, political, economic or many other reasons will spin the concepts into a pseudo science, a sophestry that tries to justify their actions. "It must be done because science says its a good idea". This was the case for example in the Nazi movement. Many new age religions use these tactics too but to different ends. In its purest form eugenics is merely the selective breeding of a population (of plants/animals (including people) to improve the genetic content of the gene pool. This is done in nature constantly and naturally, a female kangaroo will select the male kangaroo to father her children on (and I'm not an expert on the likes and dislikes of female kangaroos) how high he bounces, or how big he is or how well he performs in combat with other male kangaroos. By doing this, smaller/ lower bouncing kangaroo males wont get the opportunity to breed, and so the population gets physically bigger. (Female wallabys may select males with a good sense of humour, I don't know why theyre smaller). But really eugenics is merely the prevention of perceived weaker genomes being used in the breeding pool. If you go to a night club, you'll see the same thing happening in the human population, the athletic guys attracting the attention of the better looking girls, and the nerds being left with their choice of girls with great personalities. In society we support the weaker members and allow them to breed, in fact these days its the weaker members of society that tend to have 10 kids while the successful members tend to have 2 or less children, and therefore we are participating in a negative eugenics program at the moment. But the principle behind it is fairly solid science I feel, even if the application against the will of anyone is, as I said, evil and not something I would ever support. And when it comes to removing individuals from a breeding population that are examples of great health/intelligence but of one colour or another, then thats simply not following the process of eugenics, but as I said, racial cleansing. The Nazi's tried it with religion. How can a healthy intelligent individual be considered bad for the future of a genetic population based on his religion? Its not about genetics when it gets to that point, its about hatred. I just thought it was worth separating the 2 things for the point of discussing it rationally without emotional reactions coming into play.
 
I'm just saying that historically, in the 20th century there has been huge resistance to the idea that hybridization has been a factor in evolution.

This resistance has been primarily unscientific and irrational.

It is obvious that hybridization has played a fundamental role in evolution. biogeneticists and evolutionary biologists, are recently forming theories which validate this. Why has it taken a hundred years to confirm what Linnaeus has been saying for over 200 years?

Up until very recently(about 50 years ago) society has been racist and segragated. This racism necesarily tainted the sciences. Pseudo sciences like Eugenics and Craniology are the result of this taint.


It is not an emotional issue for me. Facts are facts, and the Modern Fields of science and academia at large, particularly Genetics, are very quick to denounce Eugenics and state that it is invalid, as well they should.

People are not horses, and as such should not be bred as horses are bred.
We have rights. And the right to choose whom we mate with is perhaps the most basic and fundemental right that we possess.
The philosophy of the Eugenicists can only lead to Fascism and mass murder on an unparalelled scale, the Nazis proved this in the 1940s.

Mendel is known primarily for his work with hybrids. The modern Hybrid Swarm Theory, certainly does not contradict any of the postulates that Mendel put forth, on the contrary.
 
Last edited:
joshuahazen said:
The more diverse the DNA to be recombined, the more natural mutations will occur...
Hybrid Vigor is a product of this function of DNA.
Click to expand...
It seems to me that Hybrid Vigor is a fundamental problem. Why does varied diverse DNA give vigor as compared to a plant that has acclimatized itself to a location? This is counter intuitive. Has anyone thought deeply about this? What holds back a plant before hybridization? What is gained after hybridization? How many generations can cannabis be breed before it gets inbreed? I noticed Nevil said you could line breed two lines of the same cross and cross the two lines to hybridize. Would that be enough to keep them from deteriorating?
 
Last edited:
The most widely accepted explanation for hybrid vigor is heterozygosis, or because they have heterozygous sets.
This explanation by itself does not seem adequate however.

Another related explanation is that vigor is caused by diserable unit characters, and since a hybrid has many more of the desirable characters within its gene sets therefore it will naturally posess more vigor.

It is something like this.

Nevil is referring to linebreeding. Linebreeding has been used for thousands of years to keep pedigrees pure, and keep them from getting negatively inbred.
Whether it can keep a given strain from getting negatively inbred over an extended period of time, like say, 100 or 1000 generations, would depend on the line itself, and the breeding strategy of the breeders. It is good breeding practice to intermittantly introduce new or fresh blood to a line every so often, through the occasional outcross, to keep it from getting too inbred.
 
joshuahazen said:
The most widely accepted explanation for hybrid vigor is heterozygosis, or because they have heterozygous sets.
This explanation by itself does not seem adequate however.

Another related explanation is that vigor is caused by diserable unit characters, and since a hybrid has many more of the desirable characters within its gene sets therefore it will naturally posess more vigor.
Click to expand...

imo because the plant have 2 different sets of genes (heterozygous), she can chose the most useful gene in each situation. becoming more vigorous.
 
I disagree that there is a fundamental difference between breeding humans and horses. Humans are a part of the animal kingdom. There is no difference between man and animal. Man is animal. We were once apes, we are still apes. These are facts. We have rights because we choose to give each other rights. Apes have rights, horses have rights, they merely organise their communities marginally differently than we organise ours. We assume they dont have rights as we feel that we have the right to do as we please with them. But thats the same as a tiger assuming the deer doesnt have the right to survive when hes hungry. We can start a sociology of interspecies thread, but lets keep it to plants as we will quickly lose sight of what we are actually discussing here.
Is it important to select the right parents to get the desired offspring? Yes. How is selection made? Depends on the desired outcome.
Outcrossing will reduce the frequency of the trait that is present in the current population unless the individual from the other population also shares the same trait that is desired. Incrossing within a population that possess a desired trait, will increase the ratio of that trait within the population that follows. Abnormalities do crop up, and thankfully so, or we'd still be swimming in the ocean without a computer to discuss this. If you like the abnormality, use it as a parent, if you dont, dont.
 
Horses are slaves, people aren't, or shouldn't be, in a free society. That's all I'm going to say about it, I agree, the topic would be better addressed in a different forum or at least a different thread.

You Make a good point GMT, and generally when a competent breeder looks for a specimen to outcross to, he might spend many years trying to find one, and generally, the outcross candidate he seeks is one that expresses the same traits he is breeding for.


Additionally he may be looking to improve his strain somehow, by finding a specimen that is strong where his line might have a weakness, or by looking for a strain that has some character which his strain lacks, but that he would like to see in his strain.
 
Last edited:
blackberry said:
imo because the plant have 2 different sets of genes (heterozygous), she can chose the most useful gene in each situation. becoming more vigorous.
Click to expand...
Hmmm. Think about what you just said. The plant chooses. How does it know what to choose? I'm certainly not disputing hybrid vigor but it strikes me as a complete mystery on why it happens. One reason I'm interested in this is breed autos and there's no going back with them. No clones. So inbreeding or loss of vigor are problems.
 
Stolen from Wikipedia, about theories to explain hybrid vigor (heterosis):

Heterosis, or hybrid vigor or outbreeding enhancement, is the increased function of any biological quality in a hybrid offspring. It is the occurrence of a genetically superior offspring from mixing the genes of its parents.
A mixed-breed dog

Heterosis is the opposite of inbreeding depression, which occurs with increasing homozygosity. The term often causes controversy, particularly in terms of the selective breeding of domestic animals, because sometimes it's inaccurately claimed, that all crossbred plants or animals are genetically superior to their parents. It's only true in certain circumstances. When a hybrid is seen to be superior to its parents, this is known as hybrid vigor. When the opposite happens, and a hybrid inherits traits from its parents that makes it unfit for survival, the result is referred to as outbreeding depression. Typical examples of this are crosses between wild and hatchery fish that have incompatible adaptations.

Genetic basis of heterosis
Main article: Dominance versus overdominance

Two competing hypotheses, not necessarily mutually exclusive, have been developed to explain hybrid vigor. The dominance hypothesis attributes the superiority of hybrids to the suppression of undesirable (deleterious) recessive alleles from one parent by dominant alleles from the other. It attributes the poor performance of inbred strains to the loss of genetic diversity, with the strains becoming purely homozygous deleterious alleles at many loci. The overdominance hypothesis states that some combinations of alleles (which can be obtained by crossing two inbred strains) are especially advantageous when paired in a heterozygous individual. The concept of heterozygote advantage/overdominance is not restricted to hybrid lineages. This hypothesis is commonly invoked to explain the persistence of many alleles which are harmful in homozygotes; in normal circumstances such harmful alleles would be removed from a population through the process of natural selection. Like the dominance hypotheses, it attributes the poor performance of inbred strains to a high percentage of these harmful recessives.
 
Yes that is right, heterosis is an abbreviate of Heterozygosis.

Oscar, it is very important that you establish several distinct and seperate lines within the given strains that you are attempting to maintain.
 
Interesting stuff.....Im interested in a solid plan to retain some good seeds from heirloom seed. Kind of got jist of it. Have F2 and F3 stock......
 
I've been thinking about hybridization. It seems very mysterious to me. Maybe hybridization upsets the plants equilibrium. I came to this idea after reading this thread here:
http://www.mrnice.nl/forum/6-breeders-support-information/6121-new-breeding-perspectives.html
and specifically this article linked from the thread:
Plants and animals can replace inherited genes with more perfect ones
Plants and animals can replace inherited genes with more perfect ones - JREF Forum

From our perspective we want potent plants with fast growth. Large colas that are so large that they threaten to break the plant. The plant not knowing we're taking care of it wants a less risky strategy. Less potency. Stronger limbs. Maybe it breeds to the average. Like a dog. Most average dogs look similar. It recombines it's own genes to effect that as it is inbreed. The important point is THE PLANT DOES THIS. When we hybridize it we throw this mechanism off temporarily. The plant doesn't know where the equilibrium is and throws out a vast quantity of phenos in response. Later it regains it's equilibrium.

Just a thought. What say you?
 
Last edited:
I think its something like that Oscar. Luther Burbank had his theories about it.
Like he developed a variety of walnut tree that grows 4 times as fast as a normal walnut tree and gets many times as large.

He theorized, that perhaps this hybrid walnut was throwing out phenotypes from millions of generations previous when trees had to grow huge just to compete.

I think there are many things going on when you hybridize. It mixes things up for one causing all kinds of previously unexpressed alleles to resurface, it also increases the likelyhood of new alleles being formed.
 
The plant wanting things is a logical fallacy. Sure in nature and in feral populations a plant that grew such fat buds it would snap in half would have a lower chance of survival. But we've been selecting this plant for thousands of years and the plant isn't "fighting back".

The idea of breeding to the average is also a fallacy that isn't grounded in an understanding of genetics.

I don't think you really understand what recombination is oscar. There is no magical equilibrium that the plants are moving towards.
 
I was referring to mutation rates in hybrids. Numerous studies in subspecies hybrid matings have conclusively demonstrated that generally, offspring from hybrid pairings have higher mutation rates than those from non hybrid pairings, both in plant and animal kingdoms.
 
Last edited:
joshuahazen said:
I was referring to mutation rates in hybrids. Numerous studies in subspecies hybrid matings have conclusively demonstrated that generally, offspring from hybrid pairings have higher mutation rates than those from non hybrid pairings, both in plant and animal kingdoms.
Click to expand...

can you put some links up please? as far as I'm aware mutations occur due to either error during meosis or from transposons on the Y, the only other way is thru viruses, chemicals and radiation.

From reading your walnut tree thing that Burbank did, I would of thought that was artificial selection at work... didn't he cross an English type with a black type?
also i think he was a believer of "the theory of the inheritance of acquired characteristics" so a bit Lamarckism...

Although the theory of the inheritance of acquired characters
is commonly believed to be a myth, several papers claiming to
have discovered examples of the phenomenon have recently
been published in peer-reviewed journals. Offspring receive
more than just a set of chromosomes from their parents. The
maternal gamete may contribute mitochondria, Golgi bodies,
ribosomes, RNA molecules, cytoskeletal fibers, and many
other interactive substances to offspring. The nuclear genome
of a diploid organism consists of the nucleotide sequences in
each set of parental chromosomes from which it was derived.
However, it is now recognized thatDNAcan be epigenetically
modified, for example, by the addition of other chemicals
such as methyl groups (Mattick 2004). Methylated sequences
are usually genetically inactive. These epigenetic alterations do
not change the sequence of nucleotides an individual inherits
from its parents (i.e., they are not considered to be mutations),
but once they are acquired they can be passed on from one
generation to the next in some organisms, including mammals.
In a gametogenic phenomenon known as imprinting,
a gene becomes inactive in progeny only if its controlling element
is methylated in the egg and demethylated in the sperm
from which the progeny developed; in other cases, methylation
of the gene might occur in the sperm but not in the egg.
Other phenomena such as horizontal gene transfer, adaptive
mutation, and behavioral inheritance through social learning
have recently been suggested as possible examples of inheritance
of acquired characters (Cohen 2004; Danchin et al.
2004; Jablonka et al. 1998; Landman 1991).
Click to expand...

Luther Burbank: Honorary Member of the American Breeders' Association
 
Last edited:
You must log in or register to reply here.
Back
Top