Pollinating hybrids for pure plants once more?

[cooky173]

I'm going to use Faucaria as my example, as this is where my hybridising experiments currently lie. I'm also putting my high school genetics into play, which I expect is correct in only the most basic of terms, and maybe not even then.

Situation 1.

Say I crossed F. Candida (white flowers) with F. Tuberculosa (warty leaves, yellow flowers)

Gen 1 plants would be kinda warty, with pale yellow flowers.

Gen 1 crosses would produce plants that are pure F. Candida, pure F. Tuberculosa, or look the same as gen 1 plants.

Situation 2 is the way I think it will actually work in practice.

Gen 1 crosses could produce any of the following:

Pale Yellow, Yellow or white flowers with either warty, kinda warty or smooth leaves. Futhermore a smooth leaved, white flowered plant wouldn't necessarily be F. Candida.

A simple reply of Situation 1 or 2 is correct is enough, but if you want to go into more detail, that would be appreciated.

Thanks

[Sutremaine]

Gen 1 crosses would produce plants that are pure F. Candida, pure F. Tuberculosa,

A cross like that could only be pure candida if the 'grandchild' plant got all of its mother's candida genes and all of its father's candida genes, and the odds of that are... rather long (plants have a lot of genes).

If you did get two hybrids that looked like one species, they'd still have genes from the other doing things that you can't see, and genes that do do things you can see but are recessive and not expressed in either plant. Cross those two species-looking hybrids, and you might get those 'hidden' genes from the other species expressing themselves again.

[iann]

You can try. Sometimes works, sometimes not. In a pure Mendelian case of a single recessive and single dominant gene you can get back to a quarter pure plants in the F2 generation as demonstrated by the recessive trait reappearing. Of course that assumes you have pure plants to start with, most unlikely for Faucaria.

[cooky173]

Ok, I think I get it.

I should have thought about it in terms of animals, when we didn't get our dogs desexed early enough a brother and sister mated, but the pups weren't copies of the grandparents.

Thanks Sutremaine and iann.

[A. Dean Stock]

Once you cross the two species and produce hybrids it is almost impossible to get back "pure" species again without many generations of backcrossing into one species line. Genes are on chromosomes and there are many of them. Each hybrid gets a different "slice of the pie" and no matter what they look like they will still have mixed genes from both parental lines (introgressed is the term).
Dean