Post by Tom Wagner on Jan 12, 2010 8:00:40 GMT -8
Guilty of cross posting, however.....
Quote:
tomatoville.com/showthread.php?t=13112
Your title for this thread over at Tomatoville.com got my attention: HUGE respect for breeders
Having spent a good part of my life breeding all sorts of plants and animals...I usually feel the negative aspects of that so-called respect; namely it is a waste of time, etc., but an occasional veneration is appreciated. So I guess I should say thanks, however I am just one of foolish folks doing this kind of work. There are quite a few people here on TVille that are dabbling in breeding, therefore they should acknowledge your respect as well.
That said, I wanted to reflect on the Davis gene bank for a moment. That link you offered for us to peruse is a complicated list of genes to digest. Allow me to discuss a few things!
The list of genes numbers about 1221. Of those about 104 are dominant and the rest are recessive. Capital letters denote dominance...lower case letters means recessive. That is a 1 out of 12 ratio of dominant to recessive. There is a reason for that ratio...most mutations are lethal or detrimental to the plant and if that gene is dominant the plant's option of survival is lessened greatly. A recessive can bonce around and be part of the population without the heterozygous line being a major problem for seed survival. There have been obviously many dominant genes that have occurred, but somewhere along the way no seed was saved of those because of its failure.
Since I have requested germplasm from the Davis site as well as others, I have been one to work with recessives a lot, in fact many of my most well known varieties are exemplary of that. But so many of those genes are just not worth it when in a homozygous plant and even if you request the seed, you will often receive a mix bag of seed: seedlings which will segregate for plants without the gene in mind, heterozygous, and homozygous. The homozygous seedlings may fail before you even get to see the phenotype of that trait or the plant fails to mature to fruition. You end up with that trait in a ugly version of a tomato plant and wonder why in the blazes you wanted it!
Male sterile lines can be maintained only in the carrier version, so that the seedlings will segregate 1:4 for male sterile lines. I could go on but I think you understand the difficulty a breeder has to fully utilize the vast majority of those genes.
Tom Wagner
Administrator's purpose: Folks want to know where to find information on breeding plants. This forum approaches this wish in real time posting, rather than rely on a book.
Quote:
After doing some morning reading re dominant versus recessive genes in tomatoes I found this:
tgrc.ucdavis.edu/Genes.html
Now THAT really raises the bar in terms of the many factors the breeders here and elsewhere have to consider!
tgrc.ucdavis.edu/Genes.html
Now THAT really raises the bar in terms of the many factors the breeders here and elsewhere have to consider!
tomatoville.com/showthread.php?t=13112
Your title for this thread over at Tomatoville.com got my attention: HUGE respect for breeders
Having spent a good part of my life breeding all sorts of plants and animals...I usually feel the negative aspects of that so-called respect; namely it is a waste of time, etc., but an occasional veneration is appreciated. So I guess I should say thanks, however I am just one of foolish folks doing this kind of work. There are quite a few people here on TVille that are dabbling in breeding, therefore they should acknowledge your respect as well.
That said, I wanted to reflect on the Davis gene bank for a moment. That link you offered for us to peruse is a complicated list of genes to digest. Allow me to discuss a few things!
The list of genes numbers about 1221. Of those about 104 are dominant and the rest are recessive. Capital letters denote dominance...lower case letters means recessive. That is a 1 out of 12 ratio of dominant to recessive. There is a reason for that ratio...most mutations are lethal or detrimental to the plant and if that gene is dominant the plant's option of survival is lessened greatly. A recessive can bonce around and be part of the population without the heterozygous line being a major problem for seed survival. There have been obviously many dominant genes that have occurred, but somewhere along the way no seed was saved of those because of its failure.
Since I have requested germplasm from the Davis site as well as others, I have been one to work with recessives a lot, in fact many of my most well known varieties are exemplary of that. But so many of those genes are just not worth it when in a homozygous plant and even if you request the seed, you will often receive a mix bag of seed: seedlings which will segregate for plants without the gene in mind, heterozygous, and homozygous. The homozygous seedlings may fail before you even get to see the phenotype of that trait or the plant fails to mature to fruition. You end up with that trait in a ugly version of a tomato plant and wonder why in the blazes you wanted it!
Male sterile lines can be maintained only in the carrier version, so that the seedlings will segregate 1:4 for male sterile lines. I could go on but I think you understand the difficulty a breeder has to fully utilize the vast majority of those genes.
Tom Wagner
Administrator's purpose: Folks want to know where to find information on breeding plants. This forum approaches this wish in real time posting, rather than rely on a book.