Sunday, September 19, 2010

Poroporo to pepino in thirty generations?

Darwin’s great idea was that plants and animals evolve through time, accumulating changes which gradually morph them from the ancestral to modern form. Left to natural selection, these changes would happen imperceptibly slowly, but given human selection it could happen quite quickly. Darwin used many examples of domesticated animals to labour this point.

A fascinating experiment of the rapidity of human selection was proposed by the Russian geneticist Dimitri Belyaev, who was interested in domesticating the silver fox. After six generations of selecting cubs for breeding based on tameness, the foxes had started to act more like dogs, and after thirty generations, not only did they behave like dogs but they looked like them too. Gone was their foxy pelage which was replaced with a soft, piebald black and white coat, floppy ears and an upright waggy tail!

Thirty generations is not very long is it? How long did it take to select for the food plants we use today? Could one domesticate a plant in thirty generations, or substantially change some of its characteristics?
To tackle the first and last question, I am going to undertake an experiment. With any luck I will have at least thirty five years of mental and physical faculties left. How splendid to sit on my rocker-chair on the porch when I am seventy-five and reflect back on an experiment which took half a lifetime to conceive, and the other half to achieve.

The subject of this endeavour is to be the New Zealand shrub – poroporo – or Solanum aviculare. The outcome I am aiming for - improved fruit size, let's say pepino, or tamarillo. The plan: starting with wild plants, selectively breed for larger fruit each generation.

Year 1:  take 40 poroporo seeds and germinate them. Plant along the entire length of the fence in my back garden. Wait for fruit to ripen completely and utterly*. Select the largest fruit, remove seeds and repeat.

I may need to cut out existing plants to make space for new cohort.

Use remaining fruit in jam.





Hopefully by selecting for larger fruit, edibility will not be compromised. Never having actually eaten a poroporo fruit, however, I cannot tell you whether they taste good, bad or indifferent. Ripe fruit are eaten by Aborigines in Tasmania and were eaten by Maori here in New Zealand - only the very ripe fruit mind you, as *unripe fruit (and all other green parts of the plant are poisonous).

One of the earliest accounts of poroporo in Wellington was by Colenso with the early pioneers using the ripe berries for jam. Were the early pioneers so desperate for something to make jam out of, or are poroporo actually very edible? I will have to come back to you on this one,  posting both the jam recipe and progress.

The following blog is not too hopeful...

David McCutcheon blogged in 2006 that he "Tasted a very ripe fruit from this plant, once is enough. I can't adequately describe how grossly bitter, sour and HOT the sensation of that taste was. It lingered for ages, I mean to say it persisted, really persisted, in my mouth and on through the digestive tract - expelling other digested nutrients afterward it totally burnt the local orifice chairing that motion. Hey, if I had passed wind just then, a glowing cloud of superhot gas would surely have devastated any fauna and flora in my vicinity. Assuredly I have done planet Earth great service with this incredibly important finding: DO NOT TASTE THIS FRUIT!"

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