Quote:
Originally Posted by Fusion_power
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.
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Different people mean different things by the word "diversity" in a biology context. Some people use the word to refer to increased heterozygosity within a single genome, rather than differences between individuals. Some people use the word to refer to the level of genetic variations available in the most common strains, rather than all available. I had several eye-opening discussions with other biologists at recent seminar series at my university, because of their varied and mutually incompatible uses of this term.
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.