06 October 2013

As alike as two peas in pod – not.

I’ve posted before about the smart way to choose female and male parents when performing a cross between two varieties with one parent dominant and the other recessive in a particular gene, so you can check the certainty of a real cross in the F1 generation, instead of having to wait until the phenotypes start expressing in the F2 generation.

But what if the phenotype doesn’t exhibit classic dominant/recessive inheritance? A couple of weeks ago I found just such an occurrence that helped me sort out a mix up in one of my F1 pea crosses.

I want to introduce the hypertendril/semi-leafless trait into snow peas. This trait is widely used in field peas, where trellising isn’t an option. These plants develop extra tendrils, which grow together, and in dwarf or semidwarf peas helps them to knit together into a self-supporting tangle that reduces lodging (falling over). In the home garden this will minimize the need for trellising –  andanything that reduces maintenance is a good thing. Semi-leafless is a recessive trait, so I crossed male pollen from Delta Louisa into the female flower of Kaspa the field pea. But when I grew the F1 seeds out, two of the six or so seedlings were hypertendril. Strange.
Hypertendril on right, normal on left

My  only explanation is that the Kaspa flower had just started to shed pollen when I crossed it, so a couple of the ovaries in that pod must have selfed with Kaspa pollen.

A further bit of evidence was the leaf margins. Kaspa has toothed edges to the leaves, Delta Louisa is smooth. The two hypertendril “F1”s (that weren’t) had toothed leaves, but the other F1s (the real deal) had slightly toothed edges. This suggested toothed leaf edges exhibits intermediate inheritance, a trait that helped me sort out this mixed up cross in the F1.

Toothed margin on right, slightly toothed on left


But I am growing out the two hypertendril F1s, just to see…

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