Quote:
Originally Posted by rubbe87
why would crossing all wild tomato species into one plant decrease genetic diversity in that plant should it not become much higher then a normal wild tomato plant?
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rubbe87, check out this page that explains some basics of genetics in tomato:
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.