Solanum aviculare - n=23

So following on from last week, where I found out that the chemical oryzalin could be used to accelerate plant breeding by doubling chromosomes - I was attempting to find out whether I needed to obtain a Growsafe certificate in order to obtain the hazardous chemical. Well it turns out that one of my work colleagues happened to be a GrowSafe Instructor in a former incarnation, and most likely has some Surfluran herbicide in his garden shed. So he may just give me a little bit, and then I can try soaking some poroporo seeds in different dilutions this coming season to see if I can double the ploidy. Maybe polyploidy could be a good cheats way to get bigger fruit, faster!

Also today I came across a 1954 paper by Baylis in the Transactions and Proceedings of the Royal Society of New Zealand 1868-1961 which discusses ploidy in Solanum aviculare (poroporo) and S. laciniatum, and guess what? S. aviculare has exactly the same number of chromosomes as humans (n = 23)!! The other New Zealand Solanum, S. laciniatum, has twice the number of chromosomes as poroporo (n = 46). This ensures their genetic isolation. Apparently most Solanaceae have only 12 chromosomes, so this is an example where polyploidy has already occurred (allopolyploidy). Baylis makes the comment that S. laciniatum pollen is larger, its flowers, seeds and stone-cell masses (in the fruit pulp) are larger, and it has deeper corolla colour than poroporo. So this means that if I were to create a straight doubling of chromosomes using oryzalin, to obtain a tetraploid poroporo, it would probably just resemble S. laciniatum. The two aren't cross-breedable back to a triploid (46 crossed with 23, divided by 2 is an odd number, so no going there). I wonder what the maximum number of chromosomes a plant can have? Is 92 a bit excessive, do you think? What about an octoploid (n=92 crossed back with a triploid n = 46 to obtain a pentaploid n=69?). I'm not sure how this would work....

Some additional reading: "Species of this group in Australia are S. aviculare, S. capsiciforme, S. laciniatum, S. linearifolium, S. simile, S. symonii and S. vescum. The 8th species, S. multivenosum, is found in the highlands of New Guinea.
For a treatment of the group as a whole see D.E.Symon (1994). Kangaroo Apples. Solanum sect. Archaeosolanum. (D.E.Symon: State Herbarium of South Australia)."

Solanum laciniatum