I have tried mass crossing cucumber on a few occasions, and the resultant F1-F? fruits are indescribably bitter (they were subjected to extreme neglect).
I came across this paper Biosynthesis, regulation, and domestication of bitterness in cucumber Science 346, 1084 (2014) here (free access if you sign up).
It is very dense, but a diagram in the supplementary materials was most instructive
My take might be wrong, but it seems, basically Bl (dominant) confers bitterness in the whole plant. bt(c) (recessive) gives non-bitter fruit, unless stressed, which then becomes bitter, and bt (non-conditional) gives non-bitter fruit even under stress. however, the recessive gene bi (recessive) switches off all bitterness.
If my interpretation is correct, an easy route to non-bitter fruit exploiting bi is
- to ensure there is at least some plants in the initial sowing that have the bi gene. taste the leaves of all the plants (a young intern is good for this noxious task) and make sure there is at least one plant expressing the non-bitter bi gene. Seriously, be careful tasting, and stagger this over a few days, since your taste buds will be blown out after a couple of nasty leaves.
- grow out the F1 - no tasting required. (or you could just sow seeds from the non-bitter plant, and taste the F1 seedlings for bitterness which would ensure you had some crosses in the growout, but your diversity might be low)
- F2 generation - sow large quantities of seed, and taste the foliage at the small seedling stage (your first intern has either left the country by now, or chopped their own tongue out, so get a fresh one to do the tasting) . Eliminate anything with bitterness, and you should have a homozygous bi (recessive) population, but with lots of genetic diversity in other characteristics.
How’s my logic? Comments please.
gm
