Forum area for discussing hybridizing tomatoes in technical terms and information pertinent to trait/variety specific long-term (1+ years) growout projects.
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June 17, 2015 | #31 | |
Tomatovillian™
Join Date: Mar 2014
Location: Greenville, South Carolina
Posts: 3,099
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June 17, 2015 | #32 | |
Tomatovillian™
Join Date: May 2015
Location: sweden
Posts: 26
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now im growing sun gold, black from tula, kumato , indigo rose, cornabel, plumtomato, and some other ones i don't know what they are. |
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June 17, 2015 | #33 |
Tomatovillian™
Join Date: May 2013
Location: Cache Valley, N/E of The Great Salt Lake
Posts: 1,244
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Basically one gene/chromosome was isolated from the wild species, and incorporated into the domestic species. The domestic species already had tremendously limited diversity because of the manner in which they were domesticated and commercialized.
Last edited by joseph; June 17, 2015 at 05:39 PM. |
June 17, 2015 | #34 |
Tomatovillian™
Join Date: Feb 2006
Location: Alabama
Posts: 2,250
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I am growing out 2 groups of F2 seedlings from a cross of S. Lycopersicum X S. Pimpinellifolium with 16 plants per in my garden. I have plants lined up to make more crosses this year using S. Habrochaites as the pollen parent.
Crossing all the known tomato species into one plant would of necessity severely decrease genetic diversity in the tomato clade. The way to increase diversity is to domesticate more of the wild species by bringing desirable genes in through crosses. S. Habrochaites and S. Peruvianum have the most potential for stress tolerance genes and for disease tolerance. S. Pimpinellifolium and S. Galapagense have the most potential in very close relatives to the domestic tomato. |
June 18, 2015 | #35 | |
Tomatovillian™
Join Date: Jun 2012
Location: Minnesota
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If you crossed all the wild species into the domesticated plant, the resulting plant would likely have more heterozygous loci in its genome... but the vast majority of the genetic diversity in the parent species would have been discarded by the time you got to the final plant. As well, every time you selfed the plant, it would on average lose half of the heterozygous loci it had. What you really need to maintain diversity (total genetic variation) over a long term is many independent lineages, each composed of a mix of interbreeding individuals. ...exactly the opposite of how people [generally] breed plants.
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http://the-biologist-is-in.blogspot.com Last edited by Darren Abbey; June 18, 2015 at 03:42 AM. |
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June 18, 2015 | #36 | |
Tomatovillian™
Join Date: May 2015
Location: sweden
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June 18, 2015 | #37 |
Tomatovillian™
Join Date: Feb 2006
Location: Alabama
Posts: 2,250
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There are 13 wild tomato relatives that can be crossed with domestic tomato. Embryo rescue is necessary with about half of them. That means you are starting with 14 separate genomes, some of which have more diversity than all of the others combined. (S. Peruvianum) When you combine all of them into a single plant, you have of necessity limited yourself to 2 specific genomes. Selfing that plant will cut you back down to 1 genome. So from 14 highly diverse genomes the result is a single genome with most of the diversity lost along the way.
As Darren Abbey said above, the way to increase diversity is to include as many breeding groups as possible. The more plants in the interbreeding population, the more diversity retained. There are lots of genes that should be eliminated. For example, S. Habrochaites has a huge cold tolerance gene on chromosome 12. Domestic tomato has very little cold tolerance. It makes sense to eliminate the chromosome section from domestic tomato and keep the one from S. Habrochaites. |
June 20, 2015 | #38 |
Tomatovillian™
Join Date: Jun 2012
Location: Minnesota
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One plant produced from inbreeding over several generations (the conventional way of breeding tomatoes) will have no genetic diversity at all, by any definition of biological diversity. You need heterozygosity, multiple plants, or both.
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June 20, 2015 | #39 | |
Tomatovillian™
Join Date: Feb 2012
Location: Newfoundland, Canada
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http://kdcomm.net/~tomato/gene/genes.html In the visual example that's given, the two different alleles are reperesented as green or blue 'half-eggs' representing the genetic content for one trait in a given tomato plant. In the case of wild tomato relatives, there may be different alleles for the same trait, which aren't found in domestic tomatoes. So for the leaf shape example, suppose there are several, or a dozen different leaf shape alleles other than RL and PL, which could be represented as different colour 'half eggs' as shown in that page. Lets say yellow and red and orange 'half eggs' are also needed to represent all of the leaf shape alleles that exist amongst tomato and relatives, and the diversity of possibilities in any given plant. But in any given plant, there can only be two alleles at one time (represented as the two half eggs of any colour combination you like). If you have yellow and blue, there's no place left on the "locus" for alleles represented by green and red. If it is a hybrid with two alleles carried, you can cross it with anything else but the offspring can still only have two different alleles max in the single plant. And after it self pollinates for a couple of generations, it will eventually gravitate towards homozygous state ie the same allele is represented twice while the other is lost, and you have conserved only one of many possibilities that existed for that trait. This is why we need seed banks and breeding programs with as many different varieties (and relatives) as possible to conserve all the alleles and genetic diversity in the tomato. |
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