Ulluco: 500

This has been another exciting year on the ulluco (Ullucus tuberosus) front.  Last year, I was able to collect almost 100 ulluco seeds, which is a rather rare event.  The last published work in English that reported production of ulluco seed was in the early 1990s, although there are some publications in Spanish that at least suggest that more seed has been produced in South America since then.  Anyway, you get the idea: ulluco seed is not all that common.
As of yesterday, I have collected more than 500 ulluco seeds in 2014.  The news is even better than that, because I collect entire inflorescenses with seeds forming and wait for them to mature.  I have eight small jars of ulluco inflorescenses that should conservatively yield another 300 seeds and there are still many seeds forming on the plants.  It seems likely that I will collect more than 1000 seeds and it is not inconceivable that I could end the season with a total in excess of 2000.
500 ulluco seeds

So, this year has shown that we can repeatably produce ulluco seed here and potentially in quantities large enough to support a substantial breeding effort.  I have also collected seeds from nine varieties this year, which is a big increase over the two varieties that set seed last year, although most of those varieties have produced a very small number of seeds.

That is the good news.  The bad news is that the majority of these seeds will never grow an ulluco plant.  A few weeks ago, I dissected 100 ulluco seeds and found the majority of them empty or nearly so.  Only 1 in 7 seeds contained an apparently mature and well-formed embryo.  So, these 500 seeds will probably yield no more than 70 mature embryos and, given the great length of time since ulluco has commonly reproduced sexually, many of those are bound to fail.

Ulluco embryo undergoing a simple paper towel germination test

Knowing what I know now, I plan to try to start the majority of the seeds this year through embryo culture.  If you aren’t familiar with the idea, it is pretty simple: You cut open the seed and remove the embryo.  You then put the embryo in a sealed container on a gel medium with some basic vitamins and minerals and a little bit of sugar.  The only tricky part is keeping things sterile so that you don’t instead end up growing a fungal or bacterial culture.  If you do everything right, you have basically produced an artificial seed.  Although it is more work up front, it eliminates the waste of trying to grow empty seeds and allows me to see what is going on.  Observing the response of the cultured embryos to conditions may help to determine just what the proper growing conditions are.

(Incidentally, the 14 well-formed embryos that I found in the first 100 seeds have been deposited into both sterile cultures and simpler wet paper towel tests and I hope that they will eventually grow.  They have certainly imbibed and increased in size, but no further development yet.)

I’m feeling pretty confident now that I will be able to get some ulluco seedlings.  Hopefully I can get some to grow over the winter and have plenty of material to plant out next year.  Cross your fingers!

(Update: Just 5 days later, September 17th, we passed 1000 seeds.  That means about 140 seeds that at least have a shot a germination.  The odds just keep getting better!)

One Response to Ulluco: 500

  1. Grammy October 2, 2014 at 7:21 pm #

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