Great Ocaspectations (1) Overdosing on Oca

Here's a view of my oca seedling bed as it looked a couple of weeks ago. Each pot contains a single seedling raised by yours truly this year, from the seeds I harvested last autumn. It may or may not be an idle boast, but I reckon that I've now got the largest collection of oca germplasm in the whole county of Cornwall. It all looks uncharacteristically neat and tidy, which rather belies the frenetic panic with which they were planted a few weeks ago.

Some friends had invited us over for tea in their lovely moorland garden. It was a glorious afternoon, with the hot and penetrating sunshine moderated by a pleasant breeze and an almost alpine aspect. I was aware that afternoon was passing into evening, but the sandwiches, cakes, drinks and good conversation made the thought of lifting my corporeal bulk from the lounger even more unappealing. The sun's rays were weakening - and so was my enthusiasm for oca planting exploits. Oh well, tomorrow perhaps? I was gently but firmly reminded of my promise to get the job done. Suitably chastened, I hurried home to collect seedlings, pots and other equipment and get to work.

Working feverishly to plant and label them all before the remaining light faded, I was reminded of Kirosawa's film Dersu Uzala. In one memorable scene, the Nanai hunter saves the life of the Russian army officer Arsenyev by rapidly building a reed hut to protect them when they are caught out by an unexpected twilight blizzard. If I'd stopped daydreaming and searching for poetic comparisons, I might have got it finished a bit sooner. Thanks to the diminishing light levels I can be fairly certain that my attempts to distribute the seedlings randomly have been successful - if more by accident than design.

By my calculation there were approximately 80 oca seedlings to be housed - the products of semi-controlled crosses - that's to say I knew who their mothers were, even if their dads were strangers to me. I attempted to grow ten seedlings or more of each variety, but some failed to come up or were scythed from below by damping off fungi. That's life. Each seedling from a known mother bears her appellation, RX0909 for instance and then an additional number to distinguish the siblings from one another - 1,2,3 etc.

Ah, but I'd reckoned without another 40 seedlings whose parentage was entirely unknown and I had sown during a what-the-hell moment back in the early spring. Suddenly there they were, pleading with me for a stay of execution - till the autumn at least. There was only one thing for it - I'd have to fit them in somewhere, somehow. No wonder I was working at such a breakneck pace. These seedlings I gave designation RX1001 , 02 and so on. I planted them nearby, turfing out, literally, some other less worthy candidates, a bunch of chillies. What is abundantly clear is that this relationship is entirely one-sided - I am at the beck and call of the ocas. I am their dutiful slave. They've domesticated me.

The canes are there to help prevent the plants from sprawling over and through one another and will also allow me to access the flowers and pods more easily - I hope. The pots will, as they did last year, keep the tubers of each variety separate. Under ideal circumstances I would have been able to give each seedling plentiful root run and space from its neighbours and planted them directly in the ground. Unfortunately, that luxury seems to have eluded me yet again. Anyone who has tried determining the provenance of stray oca tubers scattered through a Somme-like plot will know why I have opted for this horticultural apartheid. I have earthed up the stems once so far and will do so again, in the hope that this will encourage the development of tuber-bearing stolons, just like with potatoes. The bare soil, by the way, will be mulched in due course.

What with these seedlings, the tubers from last year 's seedlings, the wrinkled old retainers and new arrivals courtesy of Frank van Keirsbilck, I must have planted around 140 genetically unique individuals this season. Frank managed to get good germination from the seeds produced by my plants of "Pink Dragon", the variety he raised a couple of years ago. So that adds another 90 or so individuals to this newly evolving secondary centre of oca diversity in NW Europe. I hope we're getting up to the kind of numbers where we might start to see some interesting new traits appearing. We're also reaching the point at which some serious winnowing of duds needs to occur.

But before I get too trigger happy, it is probably as well to pause and consider what combinations of which traits might actually be desirable in those oca seedlings that escape the indignity of being untimely ripped from their pots. Here goes:

1) Early tuber formation during long days/ high yield (large tubers)

2) Profuse and early flowering

3) Vigorous and disease resistant

4) Good tuber quality and flavour

1) The main obstacle to oca's adoption as a food crop at our latitudes is its inability to form tubers during the long days of summer. A handful of marbles harvested in October can only lead to unfavourable comparisons with the potato and contribute to oca's notoriety as an "experimental crop". No, this just won't do: I'm looking for day neutral forms, or ones that can tuberise when days are significantly longer than 12 hours. I won't rest until I find one, preferably several. Perhaps I ought to set a harvest date some weeks before the end of September, lift the plants and keep those bearing the largest tubers.

2) At this stage in the game it is vital to obtain precociously floriferous plants with the ability to set a plentiful crop of pods. Seeds contain novel and unique combinations of genetic material and are the raw material upon which selection, natural or otherwise, works. Can't have too many seeds.

3) Vigour and disease resistance are also very important. Differences in vigour start to show early on in a seedling's life. I suspect vigour could be linked to early flowering and - maybe - early tuber formation. If some seedlings are small and puny and prone to damping off, chances are their offspring will inherit this weakness. I'll weed them out, so that their contribution to the next generation is nil. I'll be watching disease and pest susceptibility too.

4) At the moment my main concern is to get plants that reproduce efficiently, both sexually and vegetatively. That said, I ought to check that the tubers resulting from my mini breeding programme are of acceptable quality and are not too bitter, fibrous or unpleasant in any other way.

In my next post I will discuss what little I know about oca genetics and how I might use this knowledge in my breeding programme.