"Nick Maclaren" wrote in message
...
In article ,
Ophelia wrote:
"David Rance" wrote in message
...

I have had some black runner bean seeds now for over ten years. They
originally grew from the usual two-coloured ones but I thought that
black was unusual so I selected them and now always grow them.

Occasionally they revert to the normal two-coloured seed but mostly
they are all black. And a pod of two-coloured seeds would come from
the same plant that produces the black ones.

I've no idea what variety they are.

Do they taste different and do they keep their colour when cooked?

No, they're exactly the same. Since we always eat them as young green
beans the seeds haven't yet got their mature colours. (This applies to
the normal coloured ones as well as the black.)

Ok, thanks, David. What makes their colour change?

Dunno! Better ask Mendel!

Hmmm a little too late I fear ;-)

However, there are a few people around who have learnt from his
work :-)

It's impossible to tell which of the possible explanations is
the case without serious investigations, but there are several
common causes. My borlotti means used to be about 2/3 light,
but have drifted to being almost all light - a bit like
ladybirds, they have both dark patterns on a pale palette
and the converse.

For example, it can be caused by a fairly rare recessive gene,
so it rarely happens but will breed true when it does. And,
unless there is selection against that gene, it can remain
at low levels in a population for very long periods.

Thanks, Nick That makes sense

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