Sunday 22 May 2011

Potato blessings

An unnamed/unidentified South American andigena potato. The carmine-red splodges in the leaf axils give a clue to the deep red tubers it will produce.

So here's some positive stuff I've been getting on with. I've had some very generous potato donations from Rhizowen and Frank Van Keirsbilck, which I'm watching with great excitement as they grow. They include several colourful specimens of South American andigena (I think) types, a rare phureja variety, and some Maori (Taewa) potatoes which Frank grew from seed sent to him by a gardener in New Zealand. Being seed-grown they are "Frank originals" rather than named varieties, but I am happy with that. To me, a reshuffling of the genes of Maori potatoes is just as interesting as getting hold of existing heritage types, because it shows a lot of detail about the ancestry of these potatoes as the various parental traits segregate out. I'm very excited about them as they are very hard to get hold of outside New Zealand. It's a little difficult to tell what the spuds will look like, as all potatoes at this time of year look like brown wizened prunes regardless of what cheerful colours they might have had at harvest, so I will have to wait and see. But one seems to be a dusky ultra-purple and another a reddish bicolour. Among the South Americans there is a similar range of colour loveliness, including an unnamed pink and yellow bicolour and a black and tan bicolour called Puca Quitish. It's going to be a fun year for bizarre-coloured mash in the Rebsie household.

This is Pastusa Amarilla, a phureja-type potato from Owen. As the tubers were small I started them off in modules, where they grew like rockets, and this one had already begun to set some tiny tubers of its own by the time I planted them out.

I've not yet had time to blog about my TPS-grown potatoes from last year, and there's so much to say I don't know where to start. There were lots of fascinating colours and exquisite flavours, and some amazingly high yields considering the plants were seedlings and not grown from tubers. A great many tubers produced by last year's seedlings are now replanted and growing for the first time as tuber-grown plants. Some are HUGE ... in fact the biggest and most vigorous potato plants I've ever grown. This may be down to the fact that freshly created potato varieties are relatively virus-free. The more established varieties, unless you get planting stock which has been "cleaned" in a laboratory, will have become burdened with a collection of energy-sapping pathogens over the years. It could also be an effect of hybrid vigour, but that's probably less of a factor in potatoes than in other plants, because essentially all potatoes are hybrids. Their tetraploid (doubled chromosome) structure keeps their genes banging around like a pinball machine in every seed. Hybrid vigour is the norm in most potatoes, which is why they're such a successful food crop, and you should theoretically only see a drop in vigour if you inbreed them, i.e. grow seeds which have self-pollinated. But in an illustration of how nature likes to raise two green fingers to such predictions, the most rampant batch of triffid-aspiring monster spuds I currently have in the garden is an inbred line from self-pollinated berries of Mr Little's Yetholm Gypsy. These little beauties deserve a whole post of their own as they are wonderful, colourful and precious.

One of the most interesting potatoes-from-seed I have on the go is from a cross of primitive stenotomum cultivars, Pirampo x Khuchi Akita. This is an F3 "novelty line" from Tom Wagner, a cross of two traditional Andean potatoes which are not adapted to temperate zones such as Europe but are still fun to experiment with. I have been erroneously describing them as Bolivian, when in fact only Khuchi Akita is from Bolivia, and Pirampo originates in Peru. Any road, this hybrid is diploid, so it lacks the chromosome doubling which gives cultivated potatoes their big tubers and high yields. It's also limited in its ability to set tubers in the British climate, so I couldn't be sure that the plants I grew from TPS would give me any potatoes at all. But they did give me one very big surprise. They were completely and quite astoundingly blight resistant.

Last September I watched as all the potato haulms in the garden turned brown and rotted, including the ones which I was trialling for possible blight resistance as they had been bred to contain the resistance genes. Fortunately the blight in 2010 was late enough that it didn't curtail tuber production, and I got a good harvest, and was able to simply stand back and watch to see how the blight affected different varieties at different speeds. I had twelve plants of Pirampo x Khuchi Akita, in various parts of the garden, and there was not a speck of blight on any of them. They just sat there defiantly while the plague raged all around them, and then, as a final "sod you" gesture to Phytophthora infestans they put on a second flush of flowers just as I was scraping up the blackened corpses of every other potato in the garden. They were still flowering in October when the first frosts came. Their flowers were beautiful too, have a look at these ...

Pirampo x Khuchi Akita potato blossom, 2010.

I was really surprised, because I wasn't expecting this hybrid to show any blight resistance at all. There are a few species of near-wild Andean potatoes which are blight resistant, but not these; these are technically the same species as normal cultivated potatoes, just a less developed form of it. I'm still not entirely convinced that the resistance is genetic, and will have to see what happens to them this year before I allow myself to get too excited. But it does at least illustrate why I'm keen to experiment with unusual varieties like this.

As it turned out, about half the plants managed to set tubers. This is a pretty good achievement for an Andean landrace type, because they are dependent on daylength, and the long daylength in Europe is completely wrong for them. Consequently they don't start to tuberise until the days shorten in the autumn, by which point they don't have time to do anything before the frosts hit them. What I'm looking for in these plants is the odd one or two which can tuberise successfully in our long summer days. It's one of those things which is self-selecting by default and doesn't require much intellectual input from a plant breeder – if it doesn't tuberise effectively then it can't survive to the following year. Extreme Darwin in action. Another self-selecting trait is the keeping quality, since a short shelf-life is common in Andean potatoes. It's often possible for farmers in South America to grow a continuous cycle of potato crops, perhaps two or three a year, so they don't need to be stored for any period of time. They are just replanted shortly after harvest and off they go again. Can't do that in England though, unless you want to grow a crop of frost-bitten stumps. So I can only regrow the ones which stay alive in storage for six to eight months. This weeded out several of my Pirampo x Khuchi Akita beauties, unfortunately.

The tubers I got from the plants were small, deep-eyed, immensely variable in size (but still small) and not very abundant. However they did come in some absolutely glorious colours and markings, mostly reds, purples and intense carmine pinks.

Alas, this beautiful purple bicolour was among the ones which didn't make it through the winter. I didn't even get a chance to taste it as it was so pitifully low yielding. But I feel blessed to have had it enter my life, however briefly.

This one was a lot more promising. It's a bright red one with yellow eyes, though it doesn't look its best in this shot because it's unwashed. (Washing potato tubers considerably reduces the chance of them keeping over winter.) This was by far the best yielding of the lot - a pretty respectable harvest for a diploid landrace type. Only the largest tubers succeeded in surviving over winter, but survive they did ...

And this is what they look like now, blossoming like mad already. Notice that the flowers are more of a mauve colour than the magenta-purple blossom shown above. The flower colours did vary somewhat between siblings in this hybrid, though they were all somewhere on the mauve to purple spectrum.