On 26/09/2016 13:27, Jeff Layman wrote:
I pricked out 60 seedlings of Amsonia hubrichtii yesterday (seeds from
my own plant), sown in spring. I was most surprised to see that there
was a marked variation in stem colour; five in six were deep pink, the
rest were a pale green. There was no difference in size.

I have never seen this sort of variation in colour before. I assume that
A. hubrichtii is self-fertile - it's not exactly a common perennial,
although I have seen it for sale at the odd garden centre. I haven't
seen any other Amsonia plants around, even tabernaemontana, which is a
lot more common and might cross-pollinate hubrichtii.

Any explanations for the variation in colour, and the 5:1 ratio?


The obvious explanation is that the parent plant is heterozyous for stem
anthocyanin (or other pigment, but google provides a citation for the
presence of anthocyanins in Amsonia) production, and a proportion of the
seedlings are homozygotes for the recessive allele. Perhaps you'll later
find a pleiotropic effect on flower colour.

The expected mean ratio of offspring from a self-pollinated diploid
dominant/recessive heterozygote is 3:1. 50:10 isn't that far off 45:15 -
you'd need someone with more current statistical expertise to say
whether the difference is statistically significant for a sample of that
size.

--
SRH