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.

Sunday, 27 March 2011

Tomatoes of past glory

OSU Blue Fruit
OSU Blue Fruit tomato. Not yet commercially available (to my knowledge), this is a breeding line of purple-black tomatoes developed at Oregon State University in the US. The fruits ripen to a deep coal black but are perhaps at their most beautiful during the ripening phase when they take on some magnificent purple tones. The flavour is decent enough, although work is still being done to improve it. And no, they are not genetically modified: the colour was achieved through traditional breeding methods by combining three genes found in South American wild tomatoes.

I have been rather quiet on the blogging front haven't I? The reason is that I'm now working full time for a small publishing company, and also writing a book about potato breeding which will be available in late summer or early September. The book will answer all your questions about growing from TPS and potato seed saving, and to the best of my knowledge will be the first book of its kind on the subject. It's all very exciting and enjoyable, but as you can imagine I am immensely and obscenely busy, and working some very long hours.

Today however, I'm closeted indoors as it's the first warm and sunny weekend of the year and that inevitably means the neighbours are having a barbecue. There's nothing like the stench of burning flesh to send me scuttling back into the house with all the windows shut; so here I am, and may as well do something useful like posting some of the tomato pictures I took last year and didn't get round to using for anything. All of these were grown in the greenhouse unless otherwise stated.

Darby Striped Pink/Yellow
Darby Striped Pink/Yellow. This came from the Heritage Seed Library and is an absolute corker. It's actually an English-bred tomato, from the breeding work of Lewis Darby at the Glasshouse Crops Research Institute in Littlehampton in the 1950s and 60s. Dr Darby also produced the well-known striped variety Tigerella (a variety which I've seen described around the internet as a poor performer, which has not been my experience of it at all - it would seem that it grows better in the UK than in the US, which has led many American gardeners to be disappointed with it). Anyway, this Pink/Yellow line was never released as a commercial variety, which is a shame, because it is fantastic. The flavour is exquisitely rich and fruity, the texture is just right, the yields are very generous and the rounded fruits are a lovely deep pink-red with yellow stripes ripening to orange. It's definitely one I will grow again, and it has such a lot going for it.

Tangella. Another of Dr Lewis Darby's creations, this bright orange tomato was released commercially and enjoyed some popularity in its day, but was subsequently deleted from the National List and is now rare. Once again, it was the Heritage Seed Library which supplied me with seeds. I don't rate the flavour of this one as highly as the Pink/Yellow variety above; it's milder and mellower, although it does have a tang to it. It is very firm on the outside but has a very soft texture in the flesh, bordering on the mushy when fully ripe. But it is a nice variety, and the colour is absolutely gorgeous ... a vibrant deep orange all the way through and probably high in carotenes. The fruits come out at a variety of sizes and are a rounded apple-shape, and being bred in England, it is very happy with the UK climate.

Tomatito de Jalapa
Tomatito de Jalapa. Another one I'd recommend. This tiddly tiny cherry tomato was given to me by Patrick Wiebe at Bifurcated Carrots, but previously came from Frank Van Keirsbilck in Belgium. The thing that makes it special is that it's supposed to have blight resistance. Others who have tried it have had mixed results, some finding it blight-resistant and others not, with an additional observation that it needs to be deprived of any kind of feed or fertiliser in order to work its anti-fungal magic. My own experience was that it was blight tolerant rather than blight resistant as such. I grew it outdoors with full exposure to the elements, and gave it no fertiliser or special treatment. I also grew a normal non-resistant variety beside it as a 'control' ... not very scientific, but it gave me something to compare it with. Tomatito de Jalapa held off the blight better than the control plant did, and succumbed at a much slower rate, and although it did become infestans-infested, what was interesting was that the blight didn't get into the fruits, even when the stems they were growing on became blighted. Thus the plant was stricken with blight but I was still able to go on harvesting the fruits for some while - unlike the control plant, whose fruits rapidly became inedible. So this is definitely one to try if you want to grow outdoor tomatoes and be fairly confident of getting a crop. Having said that, the blight was a bit later in 2010 than it has been in previous years, so it remains to be seen how it will cope in a "bad" blight season. However, there's more to a variety than disease resistance, and Tomatito de Jalapa has a lot to recommend it. The small fruits are absolutely delicious - sharp and fruity - and borne on long trusses which ripen beautifully in the English outdoors. Productivity certainly didn't suffer much for the lack of fertiliser. So although the tomatoes are tiny, you get a constant supply over a long period, and overall yield is high. I'll certainly grow it again.

Essex Wonder
Essex Wonder. Popular in the 1930s as a market garden variety developed especially for the glasshouse industry in Essex, this is another "deleted" variety rescued from near extinction by the Heritage Seed Library. This crop was grown outdoors, which wasn't really ideal for it, but it coped. I've had better results growing it in a greenhouse in the past. It's a classic tomatoey tomato; in other words it's almost perfectly spherical, bright red, and has a nice old-fashioned tomato flavour. The size varies considerably, as does the thickness of the flesh, and the gel around the seeds is distinctly green.

Anna Russian
Anna Russian. An oxheart-type tomato. Oxhearts tend to be large, strawberry shaped and immensely fleshy, with few seeds. They also tend to be a bit on the bland side, and that's where Anna Russian is a glorious exception, being very rich and flavoursome. The fruits are a deep dark rosy pink with a mildly ribbed surface, and bright red inside. As they're so fleshy (and tasty) they work extremely well in slices and would probably be good in sandwiches. Yields are pretty respectable - higher than you'd think from the rather floppy plants - and early maturing. Despite the name I believe this variety comes from the US, though it may well have been taken there by Russian immigrants. My seeds came from Association Kokopelli in France. Sorry there's no bottle-top for scale in this picture, but the fruits are of quite variable size.

Pink Freud F4
Pink Freud F4. One of my own little projects which I'm quite pleased with. Now in an F4, it produces masses of miniature shiny silky Roma-plum tomatoes on large trusses, dark pink before ripening to deep red. The flavour is fabulous, and they are equally good raw or stewed up into a luxurious sauce. They also have incredible keeping properties, and ripe fruits can be left in the kitchen (unrefrigerated) for weeks on end with no loss of quality. I've no idea who its parents were, it arose from saving and selecting seed from a punnet of F1 hybrid tomatoes I bought in Marks and Spencer's in 2002. A great example of why you should ignore the received wisdom that saving seeds from F1 hybrids is a waste of time. On the contrary, "doesn't come true from seed" is another way of saying "has lots of exciting diversity". So if you grow any F1 hybrid tomatoes, either from seed packets or supermarkets, do try saving their seeds and see what surprising and delightful goodies they throw up for you.

Pugliese Green
Pugliese Green. Perhaps this should be re-christened Pugliese Red. I was given the seeds by Jeremy Cherfas of Agricultural Biodiversity, who is living in Italy and bought the fruits at a local shop. They are thought to be a locally-developed variety from the Puglia region of Italy (the heel of the boot). I grew them in 2009, allowed them to ripen to a full vibrant red, and was absolutely knocked out by how good they tasted. Really one of the best-flavoured tomatoes I've ever tasted. But when I blogged about it last time, Jeremy informed me that this isn't how they are eaten in Italy. As I should have guessed from the fact that he called them Pugliese Green, they are supposed to be eaten while they're still a bit green. So this year I tried it. And yes, they are indeed very tasty while green-ish. But I still maintain that the really knockout flavour develops when they are fully ripe! It's also remarkable how rapidly they ripen. One minute they're sitting there with no more than a blush of red, and the next day when you go to check them they are bright as a post-box. The fruits are medium sized, firm to the touch, and take the form of slightly flattened globes. The photo shows a couple of fruits in the intermediate semi-green stage as well as the full red. Take your pick. The fact remains that this is a very fine tomato, whatever colour it is when you eat it. Thanks Jeremy.

Isis Candy
Isis Candy. Popular in the US but pretty much unknown over here (I bought the seeds a few years ago from an American seed company), this is a little treasure, and actually originated in Eastern Europe. It's a small tomato, but not small enough to call a cherry; it's very rounded and elegantly symmetrical, globe-shaped but distinctly flattened. It's thin-skinned and very juicy, and has a really lovely sharp tangy flavour. It's also very beautiful, passing through many shades of orange, pink and red, sometimes in marbled combination. A regular favourite.

Green Zebra
Green Zebra. A green-when-ripe stripey tomato bred by Tom Wagner in the US and released in the 1980s through his TaterMater seed company. It can now be found in catalogues worldwide, and is widely grown and well loved. Fruits are a decent size and exquisitely striped, with more of a mottled pattern underneath. People often ask how you know when it's ripe, and the answer is that the lighter stripes change to a golden colour, which is quite distinctive when you see it. You can also give the fruits a little squeeze if in doubt. It does taste slightly different from a red tomato, and has quite a sharp, acidic tang.

Banana Legs x Green Tiger F1
Banana Legs x Green Tiger F1. Another of my own breeding projects, this time from a cross I made between one of Tom Wagner's creations, Banana Legs, and a Marks & Spencer's commercial variety, Green Tiger (not to be confused with Green Zebra above). Banana Legs is a light yellow elongated tomato with silvery stripes and a distinct nipple on the end, while Green Tiger is a perfectly spherical, smooth and shiny tomato with deep burgundy red flesh and dark olive-green stripes over its red skin. What I find fascinating about this F1 hybrid is that it's in almost every way an exact intermediary between the two parent types. It's got silvery-green stripes (not very clear in this photo as they stand out more when unripe), and the shape is an extended globe with a small nipple. This half-way blend fascinates me because it's not something that happens in my pea-breeding projects. With peas, the dominant genes assert themselves completely in the F1 hybrid, with recessive traits completely hidden until they start segregating out of the F2. I'm not a tomato breeder, I only have an occasional casual dabble, so it intrigues me to see how differently the genes express themselves in tomatoes. It's results like this which illustrate why it took so many thousands of years for humans to understand the processes of genetic inheritance, assuming wrongly that it was a simple "blending" process, and it also perhaps shows why it was with peas that the great breakthrough of understanding was made. Anyway, I could go on about how beautiful and high yielding this hybrid was, and that the flavour was pretty decent - but it doesn't really matter what traits it has, because I cannot preserve it in this form. Every seed is an F2 with a different genetic shake-up, so presumably when I sow them I will start getting segregation for the various parental traits rather than this half-way mix. But we shall see.

Something else interesting about my 2010 tomato crop which I will only talk about briefly as I need to do some more experimentation before I conclude anything. I took the slightly strange decision not to feed any of my tomato plants, but just to grow them au naturel, as it were. The inspiration for this was an incident in the 2009 season when I became so busy I had to abandon some tomato plants in the greenhouse - only to find months later that they were fruiting beautifully despite having no water or fertiliser, and also in immaculate blight-free health, even though blight was rampaging through the garden outside. This experience set me thinking, and then when Patrick gave me the Tomatito de Jalapa seeds with the instruction not to feed the plants as their blight-resistance only works if they aren't fed, something went ker-chinggg in my head.

So in 2010 I grew my greenhouse tomatoes without any fertiliser whatsoever, and I only watered them when they were really desperate. The results really astonished me. The plants didn't grow anywhere near as big as they would do with a "normal" feeding and watering routine, and so I suppose they produced fewer fruits too, but in terms of the number of fruits which were edible ... the yields were the highest I've ever had. This is because all the fruits were perfect - immaculate, healthy and blemish free. I had no blossom-end rot, I had no splitting (except very late in the season), I had no mouldering and squishing, and most remarkably I HAD NO BLIGHT. There was plenty of blight outside, it killed all the potatoes and the outdoor tomatoes. But the greenhouse tomatoes had none at all. It may be that they were just lucky, or sufficiently sheltered, but I don't think so ... I think they were so happy and healthy they managed to fight off all nasties. It's as if the lack of feeding enabled them to fulfil their natural potential instead of being forcibly plumped up into oversized bloaters. Another possibly significant factor: because the plants only grew to about 6ft and didn't sprawl like triffids all the way up to the ceiling and out the roof, it wasn't necessary to do much pruning at all. I just nipped out a couple of sidebuds when the plants were young and then left them to it. I'm wondering if the non-pruning also helped to keep them healthy, because this is exactly what the great Dominique Guillet asserts in his book The Seeds of Kokopelli. He reckons pruning is nothing short of tomato-abuse, and believes very firmly that the lack of pruning in his tomato crops is what keeps them blight-free.

Lots of food for thought and further experimentation here. If anyone else has any experience with growing tomatoes without fertiliser, or is perhaps brave enough to experiment with it in 2011, I'd love to hear about it.

Monday, 30 August 2010

Shetland tattie dreams

Shetland Black tatties, newly dug

Shetland Black
A few years ago I bought some Shetland Black potatoes from Waitrose and they were very tasty. They were intriguing looking things … small, elongated and a muted shiny black with pale corky spots on the skin and a 'netted' surface. Inside they had a distinctive purple ring set into the pale yellow flesh. I saved a few and planted them. They grew pretty well, so I wrote a review of them.

A short while after writing the review, I had a message from Jon who lives in Shetland. Did I know, he asked, that the Shetland Black sold in Waitrose is not the same as the Shetland Black grown by the crofters on the islands? Well no, I didn't. And when he kindly offered to send me a sample of the "real thing" it was not something I was going to turn down.

A box duly arrived with a generous stash of "real" Shetland Black tubers, and I saw what he meant. They are certainly similar to the commercial ones, in that they are black-skinned and yellow-fleshed with a trace of purple inside. But they are rounder in shape, with deeper eyes. The flesh is a stronger yellow, and instead of having a simple purple vascular ring, the purple is more diffuse and spreads into the flesh, although it still has about the same amount of purple overall. The skin is a softer charcoal black, with a slight coarseness and a few pale speckles but none of the distinctive 'corky spots' or netting of the commercial type. When the tubers sprout, the sprouts are purple rather than the glossy black of the commercial version. It is, as Jon put it, "subtly yet profoundly different".

Shetland Black potato
The Shetland Black potatoes from Shetland, as grown by Jon.

And while I find the commercial Shetland Black very well flavoured, the flavour of the local version is really outstanding. It has an exceptionally rich, strong, old-fashioned flavour with no bitterness in the skin, and the flesh is dense and smooth. The flavour is excellent when boiled and the potato holds together well without breaking up … if the outer skin is undamaged it keeps its purple colour. It also makes nice roasties, albeit rather dense ones with a thick skin. But then I guess that isn't an issue if you peel them … it's just one of my personal funny little ways that I never, ever peel potatoes.

Interestingly, Alan Romans mentions in his Potato Book that the version of Shetland Black conserved in the National Collection is considered by many Shetlanders not to be "right", and the authentic local version is described as larger and rounder with deeper eyes - exactly what I have here. Jon tells me that even within Shetland there are several more variants, some with a paler skin colour.

Naturally I was intrigued to see how the plants compared to the ones I'd already reviewed.

Standard Shetland Black on the left, "real" Shetland Black on the right.

Two variants of Shetland Black

Two variants of Shetland Black

Two variants of Shetland Black
Darker skin, yellower flesh, rounder tubers. The flowers do look fairly similar, but the difference not visible in this picture is that the one on the left is a rarity! This is the only decent specimen I've ever seen on the standard Shetland Black, it's usually a saggy specimen with wonky anthers or none at all. Whereas the one on the right flowers profusely.

"Real" Shetland Black produced very large voluptuous plants with big, dark green leaves, again quite different from the standard Shetland Black which tends towards the straggly end of the spectrum. To my delight, its flowering habits are also very different. It produces masses of blooms, large, elegant and mauve-petalled, borne over a long season. The real delight for me though is that it is a natural berry setter, loading itself up with large purple and green mottled fruits. In fact it's a potato breeder's dream. It has fertile pollen which can be used to pollinate other varieties and make hybrids. It will also accept pollen from other potato varieties to make more hybrids. And it is self-fertile, so I can also use it to pollinate its own flowers and reshuffle the contents of its own genepool without crossing it with anything else. To put this in perspective, the number of cultivated potato varieties which are fully male/female fertile is thought to be around 4 or 5%. Among the 95% of others which have compromised fertility is the commercial Shetland Black, which rarely flowers at all, and when it does its rather half-arsed mauve and white blossoms quickly drop off without producing any berries.

So I have been using "real" Shetland Black as both a male and female parent in my breeding programme this year. This is a good thing for me, because it brings interest and diversity. But it's also a good thing for Shetland Black, because one of the surest ways to conserve heritage vegetables is to pass their genes forward into new recombinations. Next year I will be able to sample such joys as Shetland Black x Salad Blue, Shetland Black x [Mandel x John Tom Kaighin], Highland Burgundy Red x Shetland Black, Marfona x Shetland Black, Congo x Shetland Black and possibly others. Plus of course the self-pollinated Shetland Black x Shetland Black, which will be interesting in itself. Potatoes can show a trace of inbreeding depression from self-pollination because nature really made them to be an outbreeder and they're not supposed to be self-fertile (the mechanism for preventing it got screwed up when they acquired their doubled genome). But in practice, self-pollinated seeds often produce really sturdy plants, just as vigorous as a hybrid would be. There's enough genetic diversity in the potato's tetraploid makeup to allow for a healthy bit of internal reshuffling.

Shetland Black berries

My guess, and I must emphasise that it is only a guess, is that the commercially available Shetland Black could be derived from this local version, as the high fertility makes it very easy to save and share seed from it, either self-pollinated (in which case it's a simple reshuffling of the same genetic material) or a cross with something else. The reason I think the local one is probably the older of the two is because of its deep eyes. Shallow-eyed potatoes are a relatively modern innovation, prized for ease of peeling, and although the deep eyes of the local variety are not proof of antiquity, the shallow eyes of the commercial version certainly suggest a more modern origin. And also, the commercial Shetland Black has such low fertility it would be extremely difficult to breed anything from it.

The crop of Shetland Black I grew this year produced tubers somewhat smaller than the ones Jon originally sent me, but made up for it by producing absolutely masses of them … the yield overall was high. My guess is that they will adapt within a year or two and start producing the full size ones. On the whole, the plants seem to be very happy growing down here.

Part of what I wanted to find out was how well the Shetland tatties would adapt to being grown this far south. To any Americans and Australians reading this, the British Isles probably seem very small, and relatively speaking they are, but all the same there's a huge difference between the clement lush greenery of south-west England and the rocky windblustered Shetlands so many miles out in the Atlantic Ocean, far beyond the northernmost tip of Scotland. Shetland potatoes are adapted to thin peaty soil overlaid on solid rock, which is naturally acidic and supports a very different range of plants from the deep sandy loam of Cheltenham, which is naturally infused with limestone.

At one time Shetland had quite a range of unique local potatoes, bred for the particular needs of the soil and climate and maintained through many generations, helped no doubt by the extreme remoteness of this group of islands. Potatoes are known to have arrived in Shetland in the 18th century and formed a very major part of the islanders' diet. In the past, whaling boats from Shetland travelled as far as South America, where potatoes are native, and it's just possible that they picked up some spuds on their travels which differed from those already doing the rounds in England and mainland Scotland. Unfortunately many of these unique local varieties are now lost. Jon says that many older people on the island remember a red potato called Marrister Red which appears to have vanished, and also one called Yell Blue. He was, however, able to send me a sample of a rare and precious survivor among traditional Shetland tatties, which hails from the really tiny island of Foula.

Foula Red
Foula is a fascinating place with a beautiful landscape - the islanders have a truly lovely website devoted to its heritage. It measures only three and a half miles by two and a half miles - you could probably walk its entire length in an hour, if it wasn't for the spectacularly steep slopes - and a population of around thirty people. It has the highest sheer sea cliffs in Britain, plunging straight down more than 1000ft. It has prehistoric stone rings and scattered shipwrecks. And remarkably for such a tiny and sparsely populated island, it has its own sheep and its own potato.

Foula Red potato

It's difficult to explain just how rugged this potato has to be in order to survive as a viable food crop in Foula. Shetland weather can be very extreme. When in 1936 the island became the setting for a film starring John Laurie (later of Dad's Army fame), the camera crew were astounded by the sight of water in a mill loch being blown 300ft into the air by the force of the wind. But when they tried to film this spectacle they found the wind so strong neither they nor the camera could stand up in it, and they ended up having to crawl back to base on their hands and knees. Magical and inspiring the landscape may be, but this is not a good environment for growing vegetables. The traditional solution to this problem is to grow them in plantie crubs - small circular enclosures made of stones and turf, where the walls are high enough to prevent the plants from being blasted away and a decent layer of soil can be maintained to supplement the thin squishy peat which constitutes the island's natural topsoil.

The Foula Red potato is rounded, sometimes slightly kidney-shaped, with very shallow eyes and a pink-red skin, having a slightly rough matt surface. The flesh inside is a pale yellow, and it doesn't have internal colouring like its Black counterpart. The sprouts are pale pink and the plants grow into fairly large sprawling specimens with unusually large and flat leaves, dark green and with a rosy blush on the leaf stems.

It does have one major drawback though. It is almost laughably low yielding. The spuds are a decent size, but four or five tubers per plant is as much as they can offer. They look so promising as you grub around the base of the plant and unearth the first voluptuous brick-red tuber, since the largest one is usually at the top. And so you eagerly scrabble through the earth to find the rest of them and … er … there aren't any.

The crofter who gave Jon the tubers said that it's traditionally a low-yielding variety and it's quite normal to get such a miniscule crop. The reason it was worth cultivating was that it showed better blight resistance than other varieties grown on the islands, and therefore ensured at least some harvest during bad blight years … an important consideration in a community traditionally dependent on its own food production.

Foula Red forming stem tubers
Foula Red is a natural survivor. This plant had its stem damaged by snails, and responded by making stem-borne tubers.

Well, when I grew my Foula Reds for the first time in 2009 they came up happily enough and made fine plants, but were almost immediately struck down by blight! Really complete, devastating blight which killed them in a couple of days. What was most strange was that they were the only plants in the garden to succumb … all my other potatoes were fine. This doesn't mean, however, that Foula Red has been wrongly labelled as blight resistant. The fact is, blight is an incredibly fast-mutating fungal disease and even the most resilient potatoes become vulnerable over time. Since the arrival in Europe of two mating types of blight which quickly got loved up, the version of the disease we are currently blighted with is a new supersonic strain which raises merry hell and simply didn't exist here before the late 1970s. Foula Red may well have had good blight resistance, but the goalposts have moved.

So anyway, fearing I'd lost this precious rare potato, I searched the soil and found a few tiny baby tubers that had just started to form. They were barely bigger than peas. But I kept them safe over winter, and in spring they sprouted, and remarkably, have given me six fine healthy plants in 2010. And this time, they have survived long enough to give me their proud harvest of a couple of tubers each.

My English-grown Foula Reds made it to full size, and are as big as the ones Jon originally sent me. The one thing that is different though is the skin texture. As you can see, the big one in the photo has got the same smooth roughness of the originals but many of the others have a crazed surface where the outer skin is sloughing off, very rough to the touch. I assume this is down to soil differences, though I'm not expert enough in potato behaviour to know what causes it.

Foula Red

And having sampled the taste of them for the first time, I found the flavour really excellent. It's quite similar to Shetland Black in old-fashioned richness, but it's milder and sweeter. The texture is lovely, dense but refined. Worth growing as a delicacy.

It might seem a bit odd to want to keep growing a variety which is both low-yielding and blight susceptible, especially as it's also quite slow maturing which makes the blight more of an issue. But I think something has been lost in the modern culture of wanting to maximise everything. Potato breeding focuses primarily towards larger yields, which is great, but there is still a kind of magic in only having enough to make an occasional treat. If the Foula Reds only produce enough potatoes for a couple of meals, fine - those meals are a special event. And there's also the fact that it's a rare type with no commercial potential and very limited distribution, which creates more of an imperative to take care of it. Local, heritage and landrace varieties shouldn't be judged by the same criteria as modern commercial ones. Foula Red may not win any accolades for its bounty or disease resistance, but it survives on an island with boggy soil and 100mph gales. Who knows when those genes for climate resilience might come in useful, or how important they might one day be for our future food security?

Something else I noticed, unless it's just the shock of adapting to a new climate: Foula Red is a late bloomer. Most potatoes start to flower around the time they set tubers, and Foula Red duly produced a couple of apologetic looking bud clusters which promptly aborted before they even thought about opening. Then it made its tubers, and then … when the tubers were already full size and the season was nearly over, it began to flower properly. Not all the plants produced flowers, only the two biggest ones, but they were a lovely surprise. Very pretty, elegant flowers in a light mauve with bright yellow anthers. They were a joy to behold. More for the sake of scientific study than any serious hope of finding anything, I plucked an anther and prodded it to see if there was any pollen in it. There were veritable plumes of it! Masses and masses of pollen. In fact, left to dehisce naturally it was dumping big white splodges of powder on the leaves underneath. It's pretty rare for potatoes to produce pollen in that kind of abundance. Excitedly, I dabbed some of it on the pistils of its own flowers, and on one or two other potatoes which were still flowering, which wasn't many at that late stage in the season. To my delight, every dabbing resulted in a plump healthy berry. So Foula Red, as well as Shetland Black, belongs with the 4% or so of cultivated potatoes which have complete male/female fertility.

Foula Red blossoms
Foula Red flowers

This is really good news. As with Shetland Black, it will allow me to make new varieties from it (if I can find a partner for it which flowers at the same time). But more importantly, it is a huge help in ensuring the variety's future survival. Tubers have a finite lifespan, and any variety which can't produce its own seed (i.e. most of them) is difficult to maintain long term. Foula Red's ability to produce TPS, either by itself or by contributing its genes elsewhere, will enable it to regenerate. Of course being tetraploid (I assume Foula Red is tetraploid) the seeds from self-pollinations will not come "true" to the variety in every detail but they are nevertheless a recombination of the same genes. And who knows, they might even throw up a variant with decent yields. Ha.

So thank you very much Jon. And all credit to the crofters of the Shetland Isles who know a good tattie when they see one.

Saturday, 7 August 2010

Proud author

Proud author

My apologies for being a bit quiet the last couple of weeks. I've just been ripening the fruits of another big project.

I've been running a small record label with Daniel, my music partner, for a couple of years and while it isn't hugely lucrative we do find it rewarding. The long-held dream, however, was always to found a small literary press. It might seem like a bit of an ambitious thing to do, but I have a publishing background and it was always my intention to make use of it. I originally worked as a typesetter in my teens, in the pre-computer age when they had phototypesetting machines whose output had to be processed in a photographic darkroom (I think that's how I became a singer, because I'm scared of the dark and used to sing all the time in there to take my mind off it). Different fonts were kept on strips of film, so when you wanted to use another font you had to open the machine and attach the appropriate filmstrip around a drum inside which had all the delicacy and charm of a piece of agricultural equipment and would nearly have your fingers off. The typesetting process made the most unbelievable noise, like a load of baked bean tins rattling around in the bottom of a metal dustbin. Once developed in the darkroom, the sheet of text had to be coated with sticky wax on the back and then cut up and arranged into a page layout by hand. If anything was cocked up, you had to start all over again. Mercifully I was rescued by a job with a major educational publisher, the one now known as Nelson Thornes, where I trained in book production (i.e. tut-tutting over other people's typesetting instead of doing it myself) and later moved on to be a graphic designer and editor, both of which I loved. When I got fed up with working for the buggers I went freelance. It's all done on Macs now of course but with the cumbersome clatter of typesetting machines still jangling my memory after 20 years, I always regard Adobe InDesign software with goggle-eyed wonder. Still can't quite believe it will let me change typefaces without snapping my fingers off.

So now Skylight Press has come into being, and after all these years of designing and editing books for other people I have one of my own. At some stage there will be Daughter of the Soil plant breeding books, but don't hold your breath on those because I haven't written them yet. The first masterpiece to roll off the press is This Wretched Splendour, a stageplay about the First World War which I wrote in my 20s. And of course there's a story behind that too.

I walked the Somme battlefields in 1996, primarily on the trail of Wilfred Owen, who is a special favourite poet. It was an experience which affected me very deeply. Everyone has seen photos of the cemeteries with rows and rows of white slabs, but until you go out there and see them for yourself you really have no concept of the scale of it. I spent a week out there picking up buttons and bullets in fields, putting my fingers into the carved names of the missing, the tens of thousands of people who were simply blasted out of existence. I collected poppy seeds from old trenches and stood on the edge of the Sambre à l'Oise canal where Wilfred Owen was gunned down. The night after attending Owen's grave I had some very deep and strange visionary dreams. In the following days and weeks they began to crystallise into ideas for a play. I was heavily involved in theatre at the time, so I was confident I knew how to write for the stage. It turned into a full length play about a group of bored and demoralised British soldiers in a front line trench whose lives are transformed by the arrival of a new officer, who uses his sense of humour to deal with the tragedies of the war and inspires them to face their fate with a new stoicism. I gave my newly finished script to a director at the Cheltenham Playhouse, who loved it and managed to get a theatre company down there to sponsor a full production. And a marvellous production it was too, which still brings happy memories to all concerned.

I also decided to try my luck further afield, so I sent out 30 scripts to major theatre companies and producers. 29 were rejected or ignored (I have a personally signed rejection letter from Alan Ayckbourn, yay!) but one London producer phoned up and said "this is brilliant, I've got a director lined up and we're staging it in February". And then things went a bit mad for a while. The play was put on at the Grace Theatre in Battersea. Susan Hampshire came to see it (she was so radiantly beautiful I'm sure she must glow in the dark) and came over afterwards to say hello and told me how she felt the best war drama is written by women because we have more empathy for its human aspects. Michael Billington from The Guardian came to see it - and wrote a spectacularly glittering review. That caught the eye of the top London literary agents who all started ringing the theatre wanting to "have lunch" with me. And at this point I kind of freaked out. I was still quite young at the time and I'm a shy and reclusive person, and all the attention just terrified me. I was frightened of the agents and didn't follow them up. And within a few weeks I found my celebrity status had evaporated as suddenly as it started. The play was forgotten and I came out of the experience with a three-year writer's block.

This Wretched Splendour

So anyway, now that the time has come to launch our small publishing venture, it seemed like a good idea to resurrect the play which has sat in my bottom drawer for 12 years. It still reads pretty well, and I've done a cover design for it which features one of the Somme poppies from my garden (though much Photoshopped). I decided to release it under my maiden name of Rebecca Wilby since that's what it was originally performed under. Should anyone be curious enough to want a copy, it's currently available direct from the printer for £8.25 (or $11.89 in the USA). I think they charge about £2.99 for postage as well, but for those who don't mind reading things on screen it's also available as a download, which is cheaper. At some point soon it will be available "from all good bookshops" as they say, but it may take two or three months yet for it to navigate the murky bowels of the global bibliographic databases.

But fear not, amid all this excitement I am still pollinating potatoes and staring at peas.

Sunday, 11 July 2010

TPS: blooms, hybrids and berrybags

Pirampo x Khuchi Akita F3
Beautiful purple potato blossom with white star points. This is seedling no.3 of Pirampo x Khuchi Akita.

My potato plants grown from TPS have started flowering, and very beautiful they are too. At the moment it's only the diploid ones which are in bloom, and although the tetraploids are starting to form buds they are a way behind.

I have two diploid lines on the go, both of them grown from hybrid seed produced by Tom Wagner and given to me by Patrick. They are Skagit Valley Gold x Thumbed Nose F1 and Pirampo x Khuchi Akita F3. Actually I also have some diploid plants from Mayan Gold OP seed I collected a couple of years ago, but those were sown a couple of weeks later than the other two and are not flowering yet.

Skagit Valley Gold is one of Tom Wagner's own varieties, derived from Andean potato lines, which makes it genetically distinct from the vast majority of American and European potatoes. It has small round tubers with orange-yellow flesh which cook very quickly, taste very special, and are high in carotenoids and Vitamin E. Thumbed Nose, its partner in this cross, is also one of Tom's own varieties but I can't tell you much about that one. I only have two plants of this hybrid and they are looking extremely unlike each other, although both have the distinctive diploid foliage. One is tall and dark-leaved with pigmentation in the veins, and hasn't flowered yet (though it has buds). The other is a bright lime green and much more compact, with little or no pigment. That one is flowering (pictured below) and the blossoms are an attractive pink mauve.

Skagit Valley Gold x Thumbed Nose with bee
Skagit Valley Gold x Thumbed Nose F1 blossom, providing some entertainment for a bee.

The flowers on diploid potatoes look just the same as flowers on tetraploids (although they seem to have some additional colour options - I've never seen dark purple blossoms on a tetraploid) but they have some practical differences. Maybe it's to do with Tom's diligence in using only the most fertile varieties in his breeding work, but these flowers are producing stupendous amounts of pollen. As you can see in the photo, they are attractive to bees. This is interesting because bees are among the natural pollinators of potatoes but I've very rarely seen them taking an interest in regular tetraploid varieties. So prolific is the pollen production on these blossoms there were plumes of it going up like a puff of talcum powder just from the beating of the bee's wings. Needless to say I've been using the pollen to make some more crosses and a single anther is enough to pollinate pretty much everything I have available. There is just masses of it.

The other thing that's different about diploids is that they're normally self-incompatible. This inability to fertilise their own flowers is genetic, and forces them to outbreed with other potatoes. The first two blossoms on this plant fell off, unfertilised, despite the amount of pollen they were chucking around, as there was nothing else to fertilise them. Now that the Khuchi Akita hybrids are flowering I've been pollinating them with that, so hopefully I will get some berries now.

Pirampo and Khuchi Akita are both rare landraces from Bolivia. I don't know much about them, the only available information being in the records of the United States Department of Agriculture genebank, which lists them both as a "primitive cultivar". My understanding is that they have been cultivated for many generations by Bolivian farmers but have never been commercially available, and are closer to wild potatoes than to modern spuds. The appeal of this is obvious - they have diversity which would simply not be found in so-called "advanced cultivars". They are both of the Stenotomum type - that is, they're what used to be regarded as a separate species called Solanum stenotomum but which is now classified merely as a subspecies or subgroup of the standard Solanum tuberosum. Confused yet? Just look at the pretty flowers!

Pirampo x Khuchi Akita F3
Pirampo x Khuchi Akita F3 blossom. This is plant no.4 in my batch, but they all have fairly similar flowers so far, varying in shades of purple and mauve.

The seeds I was given are described as being an F3. That just means that Tom has recombined the offspring a couple of times since the original cross. They have a lot of diversity, which I'm seeing more clearly because I have a number of plants ... about 15 altogether, of which eight or nine are now flowering. Most of them have flowers similar to the one shown above, a deep rich velvety purple. There are subtle variations in the purple, with some having a magenta hue and others more blue. Some have white tips on the petals. There are also some coming out mauve, again with some variation between pinky-mauve and bluey-mauve. Unfortunately the blossoms tend to be borne facing downwards, so you have to lift them up to see how beautiful they are! The plants are also varied in tallness, vigour, and the amount of colour on the stems and leaves.

I know little about the tuber characteristics of the parent varieties nor what to expect from my plants, but while I was earthing up the other day some soil fell away and I got a glimpse of a pink-skinned tuber under one of the plants, which seems to have set tubers exceptionally early. I'm not talking about the subtle rosy brick pink of a Pink Fir Apple here. I mean this one was really PINK. As in bright, vivid carmine. I left it in situ and covered it back up, but I can't wait to see what other variants these plants come up with.

I have to say, TPS is amazing stuff. The seeds are tiny and the emerging seedlings as fine as cotton threads; they have no tuber to provide them with support or nourishment. And yet in less than three months my TPS-grown plants are as large and voluptuous as most of my tuber-grown plants.

So of course I've been making a lot more hybrids for next year's seed, using various tuber-grown varieties. This berry is on a Sharpe's Express plant, pollinated with Salad Blue.

Sharpe's Express potato berry
The one berry containing (I hope) F1 seeds of Sharpe's Express x Salad Blue.

Sharpe's Express is not an easy variety to make berries with, as it is a very poor flower holder. It produces very pretty flowers when it's in the mood, of a pale lilac mauve colour. But the vast majority of its buds are thrown off before they open, and I only had one cyme of mature buds this year, of which only three flowers opened. I pollinated them all very carefully with pollen from Salad Blue. Two of them fell off before they had a chance to develop into a fruit. But one - just one - successfully set a berry. I go out every day and pray for it to stay on just a little longer and not drop prematurely. Such is the tenuous nature of making hybrids with some varieties.

There are other frustrating varieties too. Negresse, which would be a wonderful variety to breed from, appears not to produce any pollen (is anyone else having any luck with it?) Its anthers are hard and sterile and I can't get anything out of them. Congo is not much better. And my Mr Little's Yetholm Gypsy is declining to flower at all this year, casting off its unopened buds with wilful profligance. But I've also had some successes. Pink Fir Apple was being a pain in the arse, producing masses of flowers but not holding them long enough for a berry to set. Through patience and persistence I've now got quite a lot of berries on it, simply by keeping on pollinating more flowers day after day. Again Salad Blue has been the primary pollinator ... as I'm tempted by the idea of knobbly blue fingerlings. Highland Burgundy Red has given me a pleasant surprise too. I've been growing it for years and it's never once set a berry for me. However I've found its female fertility to be very high - it sets berries very readily when presented with decent pollen. I assumed it was itself male-sterile, but just out of curiosity I made a couple of test crosses, using its pollen to attempt to fertilise other varieties. To my surprise I got a berry. So I tried hand-pollinating it with its own pollen, and again, one or two berries ensued. The pollen fertility doesn't seem to be as high as Salad Blue's, but it certainly can be used as a male parent as well as a female. Perhaps the reason it doesn't naturally pollinate itself is more to do with flower physiology. It has an exceptionally long pistil which sticks way out of the end of the flower, and it also has very small compact anthers. Maybe the distance between the anthers and the stigma is just too great to enable self-pollination without assistance.

So I now have quite a lot of swelling berries on a great many of my different potato plants, all hand-pollinated and marked with colour-coded wool to identify the fathers. However, there is something I will have to watch out for. The berries are quite visible to start with but as they get heavier they tend to sag down into the foliage, and are lost from view. Some sag as far as the ground, where they're vulnerable to being nibbled at or stepped on. They also have a habit of dropping off the plant unexpectedly, which is not a problem in itself as the seeds inside will carry on maturing even when detached from the plant prematurely (within reason), but it does become a problem if there's a chance of them getting lost. If they roll away from the plant it can be difficult to be sure where they came from, and the coloured threads which identify the father varieties are very liable to get detached from them. What I need - at least for those which are most precious or easily lost - is a small and very lightweight bag to hang over the berries as they near maturity, so if they do suddenly decide to make a break for freedom I have them protected and contained. I've read about people using paper bags for this, which are certainly a cheap and convenient solution, but in the British climate that's about as much use as a chocolate teapot (and for similar reasons). They need to be weatherproof, and porous enough to let air and moisture in and out, translucent enough that I can see the berries inside and light enough not to add any extra strain on the stalks, and ideally re-usable. Here's what I came up with.

Potato berry bags
Berrybags. Not the tidiest stitching, but I think these will do the job very nicely.

They are simply made from a scrap of nylon gauze of the type that's sold for making window drapes (hence the pretty gold pattern, but that's optional) and offcuts of this kind of material can be got from fabric shops for next to nothing. I'm simply folding them over and stitching them up by hand, and very roughly, as the aesthetics don't really matter. The top edge has a piece of wool folded into it to make a drawstring, and I sealed the edges with a fray-stopping chemical goo so they don't fall to bits. They take about 15-20 minutes to make and as I'm the kind of person who never measures anything they are in several different sizes, some small enough for a single berry and some big enough for a whole cyme. The bag goes over the berry (including its coloured marker thread, to make sure that stays with the berry) and the drawstring is tied up around the stem.

Potato berry bag

Wednesday, 7 July 2010

July miscellany

Papaver rhoeas
Is there anything more beautiful than poppies at this time of year? This is one of my Somme poppies (see below) but with white flecks.

My last couple of posts have been pretty demanding in terms of time and research, so I feel the need just to blather about more casual stuff today.

Tomatoes ... what can I tell you about tomatoes?

I have a greenhouse full of 'em, laden with flowers and green fruits. I've been doing a few crosses, in a half-arsed kind of way, but I consider them very much a sideline. For one thing, I get fed up with hand-pollinating tomatoes very quickly. In principle they are exactly the same as potatoes and all the instructions I gave in my potato-hybridising post should translate conveniently to tomatoes, which are of course from the Solanum family and have the same basic flower type, except that they're small and yellow. But I find tomato pollination much more frustrating. The small flowers are very fiddly to work with, and the anthers tend to be tightly fused into a cone, so you have to separate them with a careful incision ... they can't be succulently and individually plucked like potato anthers. They are quite a bugger to get off, in fact - which wouldn't be a problem if it wasn't for the fact that they are snugly clamped against a ridiculously fragile pistil. There's none of the "green bendy bit" as described in my pea video ... with tomatoes it's an unyielding green brittle bit. I've destroyed flower after flower by accidentally clonking the pistil off as I attempt to wrench at recalcitrant anthers. Some varieties have a pistil so fine and spindly you can barely see it. And when you do find it, the pollen has to be applied so lightly and delicately, because the tiniest shove in the wrong direction and the pistil is cast aside like a green splinter. Grrrr.

Before I put you off tomato breeding forever, I should mention that I have a preference for small tomatoes, which tend to come from small flowers. Many of the larger-fruited varieties have much sturdier blossoms which are relatively easy to work with. Ever wondered why large-fruited tomatoes are so popular among hobbyist breeders? Now you know.

Just to show that I can and do get successful hand-pollinations though, here is a product of my own fair wobbly hand.

Banana Legs x Green Tiger F1

It's an F1 hybrid of Banana Legs x Green Tiger, a cross I made in 2008. Let me admit now that I know very little about tomato genetics, and made this cross very much on a whim just to see what would happen. Banana Legs is an American variety derived from the breeding work of Tom Wagner, though it wasn't raised by Tom himself but selected from a batch of mixed seed bought from his TaterMater company in the 1980s. It's a long plum tomato with a bright banana yellow skin with silver-green stripes, and yellow flesh, and attractive lacy foliage. Green Tiger is something of an enigma, as I obtained it from a packet of Marks & Spencer's eating-tomatoes, and they claim it's exclusive to them (or it was, until me and dozens of other gardeners started saving and sharing its seeds). It has a dark olive green and red striped skin, dark red flesh, and is as round and shiny as a snooker ball, but with a better flavour. Intriguingly, the F1 is producing egg-shaped fruits, which are pretty much intermediate between the two parent fruit shapes.

My tomato experiments are always going to be limited though by the fact that I don't have the space to do it properly. It's all very well having this solitary F1 plant, as you don't need to grow many plants at the F1 stage. Next year when I come to plant the F2 I will have a problem, as I won't be able to grow more than three or four plants ... so it's pot luck whether I'll get any interesting phenotypes. That's fine though ... I have enough on my plate with the peas and potatoes, and can do without too many extra projects. I'd rather give away the F2 seed, if I can find anyone who wants some, so that those with more space and more tomato passion can make use of it.

Here's another tomato curiosity: variegated Green Zebra.

Green Zebra variegation
Variegated leaves on a Green Zebra tomato.

It would be nice if this was a heritable feature, but no such luck. It's a spontaneous somatic mutation - which is the posh way of saying that nature freaked out and made a cockup in the cell division, and the cockup then replicated itself, resulting in two different types of leaf tissue within the same leaf. As the cockup is in the cells of the leaf, and not encoded in the DNA, it won't be passed on to the plant's offspring. In fact this tomato is already reverting to normal fully green growth.

And funnily enough, there is a similar thing going on in one of my peas. This is a variegated form of the already lovely Buerre Cosse Rouge. Again, I'm pretty sure it's a somatic mutation and won't be passed on in the seeds.

Variegated pea leaves

Then there's my Wilfred Owen poppies, which were pretty much the first thing I wrote about when I started this blog in February 2006, and you can read the story of them if you're interested. The gist is that I collected wild poppy seeds from plants growing in a relic of a first world war trench on the Somme. The trench was, I believe, occupied by Wilfred Owen in January 1917 and his poem The Sentry was written about his experience in it. I've been growing the Somme poppies for many years in my garden, and they are rather lovely ... deep silky bright red with a distinctive black cross at the base, though they vary in how strongly the black cross is expressed.

Somme poppy
Somme poppy, with a partial black cross.

The native wild poppies of northern France probably haven't changed much since WW1, but during its tenure in my garden the Somme poppy has taken the opportunity to hybridise with some Mother of Pearl poppies I had growing elsewhere at one time. There's not a lot you can do about this; poppies are sluttily promiscuous and will cross over large distances. And I can't say it bothers me. I'm of the view that genes are the important thing, and outer appearance is secondary. I still get plenty of "true" Somme phenotypes every year, and additionally I get some beautiful variants like this.

Hybrid poppy
Natural hybrid between a Somme poppy and a garden variety. It has the perfect black basal cross of the Somme type with the pink radial stripes of Mother of Pearl.

And finally, a whinge.

When I moved into this house/garden, there was a trellis fence along the western boundary adjoining my main vegetable plot. The previous owner, who was also a keen vegetable gardener, had made a point of having a fence there which let full sunlight through to his vegetable plot. Well, my next door neighbours just took it upon themselves, without consulting me, to remove the trellis fence and replace it with solid 6ft panels. I can see why they didn't consult me. They knew very well I would object, on the grounds that I now have a permanent shadow along a sizeable strip of my vegetable plot. They didn't even do a tidy job ... I'm sure it looks immaculate on their side but they've lumbered me with scrappy bits of wooden battens with sharp nails sticking out of the wood. As they just went ahead and did it, the only recourse I have would be to try to force them legally to remove it. Do I want to get into legal shenanigans with people I have to live next to? No, not really. But all the same, I am well pissed off.

I get on fine with the neighbours and haven't had any dispute with them before, although our garden ideals are polar opposites. Their garden is polished and scrubbed with lawns as sterile as astroturf, and mine is a voluptuous muddle. That, it seems, is the reason for the fence - the missus got fed up with untidy things from my garden growing through the trellis. They have no knowledge of the work I do with my scruffbag plot; they just find it baffling that I grow vegetables for seed and don't eat them. Why save seeds when you can get them for 99p down B&Q? The concept of breeding new varieties and conserving heritage ones meets with blank incomprehension. It's just a different outlook on gardening, and neither of us appreciates the other's aesthetic or way of doing things. At least now they won't have to worry about my dandelion seeds contaminating their garden, and I won't have to worry about their chemical sprays contaminating mine. The privacy is also a blessing. But I'm still pissed off.

Taking a fence
Yes I know it's extremely childish, but it makes me feel better.

Thursday, 1 July 2010

Hybridising peas: the video

Here's a demonstration of the method of hand pollinating peas for anyone who has 10 minutes and 39 seconds to spare. Sorry about the business with the cat, he distracted me and it wasn't really possible to edit it.

Sunday, 27 June 2010

How to breed your own potatoes

Hybridising potatoes

Breeding new potato varieties is easy. You can hand-pollinate potato flowers in far less time than it'll take you to read this article, but I'm going to attempt a reasonably thorough explanation, so I hope you find it helpful.

Potato breeding is done through sexual reproduction, i.e. pollinating flowers to produce berries which contain true seeds (TPS).  Normally when you plant potatoes you propagate them from tubers, confusingly called seed potatoes but which are not actually seeds, but root cuttings. You can't cross tubers. They can only reproduce themselves as they are. Occasionally a plant may produce a spontaneous mutation but it doesn't happen often enough to be useful as a breeding method. Flowers are the way to go, because they give you the option to combine and reshuffle genes from the parent varieties of your choice.

There's a lot to be grateful for in the anatomy of a potato flower. Hand-pollinating them is very easy. The flowers are large and easy to work with, and the individual parts are easy to manipulate.

What's not so easy is making careful plans and predictions for what you might get out of it, and that's because potatoes are tetraploid. If you've no idea what I'm talking about then have a look at my previous post about TPS for a simplified explanation. To give a one-sentence summary: a tetraploid has double the amount of genetic material that a normal (diploid) organism has, which is a bit like inheriting traits from four parents rather than two. Tetraploids are a quirk of nature but in potatoes they are a very successful one, and the vast majority of cultivated potatoes in Europe and North America are tetraploid.

You may still come across the occasional diploid. Mayan Gold and its associated varieties are diploid, and those who are growing TPS from Tom Wagner may have a few diploid lines from him. Diploid potatoes can be recognised by a tendency to have smaller and less fleshy leaves, but the most distinctive feature is the berry. A diploid potato berry has a distinctively pointed end, kind of strawberry shaped, while tetraploid berries are more rounded and tomato-like. If you're feeling experimental you can try crossing a diploid with a tetraploid. At best you will only get a few viable seeds out of it, but it's a brilliant way of introducing new diversity into potatoes. At some point soon I will give it a whole article of its own, as it's too elaborate a subject to go into here.

Potato berries
Potato berries (these are tetraploid ones) in development.

However, assuming the potatoes you want to cross are tetraploid, since most of them are, it's very difficult to predict what the resulting offspring will be like because of the genetic variability involved. With tetraploids, the convenient order of the Mendelian ratio is thrown out the window and replaced by something more akin to a gene tombola. F1 hybrids are not uniform as they are in most other types of breeding project. If you grew a lot of offspring from your cross you'd find that many traits show continuous degrees of variation through the population, rather than segregating into Mendel's either/or groups … which happens because there are so many different ways the alleles can arrange themselves. To quote a research paper by Scotland's premier spudmeisters, Meyer et al (1998) "[Tetraploid] inheritance implies the random pairing of four homologous chromosomes at meiosis, and in a highly heterozygous outbreeding species results in a large number of possible allelic combinations at a single locus. In the most extreme case, eight different alleles could segregate independently in a population, resulting in 36 possible genotypic classes in the progeny." In other words, potatoes naturally have a mixed up genepool (from outbreeding) and when they pollinate and set seed those alleles can arrange themselves in any order - with each different combination having a unique effect on how that trait is expressed. And we're just talking about an individual locus here … the same is happening at every other locus throughout the whole genome. Yowza!

In short, tetraploids are complex and contain a lot of genetic material which can be immensely variable. Scientists doing genetic research on potatoes often choose to work with diploid lines instead, because tetraploids make such a muddle of their data it's hard to interpret anything.

So where does that leave you as a home gardener or small-scale farmer wanting to develop your own potato varieties? It leaves you in a position where you may as well have fun, experiment, use your imagination, be creative. As the results can't easily be predicted, you don't actually need to know anything about genetics. Think more along the lines of what you might get if you cross this colour with that colour, or this flavour with that shape - and then be prepared to be surprised!

One piece of misinformation I see spread all over the internet is a belief that you won't get anything worthwhile out of a home-made potato hybrid because producing just one good variety takes thousands of plants and many many years. This myth has arisen from under the slow-grinding wheels of the potato industry, which does work like that. Sure, if you want to breed a variety which will be listed in all the catalogues and sold in Tesco's and will make you rich from the royalties, your chances are very slim. The selection criteria for commercial potato varieties are immensely restrictive - and largely at odds with what most gardeners would want. Commercial breeders may well churn through (and reject) 200,000 seedlings to find one with commercial potential, then spend the next eight years doing field trials with it before it's ready for release. But don't let that put you off. You can breed a good variety within two years - easily. The majority of your home-made potatoes will be worthwhile, at least decent enough to eat and enjoy and feel proud of. A few will be exciting and wonderful. Even if you're only working with a very small patch of garden, you will almost certainly get some tubers that are worth saving and growing on next year.

The beautiful thing about potatoes is that it only takes two seasons to get a completely stable new variety. So it's actually quicker than most other vegetables. You make a pollination the first year and produce the F1 seeds, which are all unique individuals because of the genetic diversity. The second year you grow plants from those seeds and they make tubers. If you like the tubers, you simply propagate them by saving and replanting them. As the tubers are basically root cuttings of the parent plant (clones) they are genetically identical. There's no arsing about trying to make F2 and F3 hybrids (unless you want to) or years spent roguing out unwanted recessives. Once you've got something interesting, it's instantly a new variety.

Pirampo x Khuchi Akita F3
Hybrid potato grown from TPS. This is one of Tom Wagner's hybrids, an F3 of Pirampo x Khuchi Akita. The parent varieties are Bolivian landraces, and are diploid.

If you've dipped a toe into plant breeding before, you'll know that plants tend to be either inbreeders or outbreeders - though that's more of a sliding scale than a polar absolute. Potatoes are really a bit of both. The natural status of potato is outbreeder. The various (diploid) landrace species from which cultivated potatoes are derived have a self-incompatibility mechanism which prevents them from pollinating themselves. The majority of diploid varieties are self-incompatible, although there are exceptions. This forces them to hybridise and mix their genes up in every generation, hence the wondrous diversity found among diploid landraces. However, when potatoes went tetraploid the compatibility barrier got screwed up somewhat. Many tetraploid potatoes have sterile pollen which can't fertilise anything at all, but others can fertilise themselves as well as each other. So they're designed to be outbreeders, but in practice a lot of flowers simply get knocked up by their own pollen.

Which gives you a choice: you can make hybrid seeds by crossing two different varieties, or you can make self-pollinated seeds which are the product of just that one variety.

Choosing parents: hybrid or OP?
Both are worth experimenting with, but for different reasons.

When a potato plant sets berries naturally without your intervention, it's most likely that it self-pollinated, but it may also have made hybrids with other potatoes flowering nearby, and you may have a mixture of selfed and hybrid seeds in the same berry. This is called open pollination (OP) … and the results are basically pot luck.

Making a deliberate hybrid is the most usual way to breed a new variety, as it introduces a lot more diversity. The basic method is to emasculate the flower to stop it from pollinating itself (which you don't even need to do if it's one of the many varieties with sterile pollen) and fertilise the female part of the flower with some pollen from a different variety. The offspring will be very varied, but that's the fun part and you should also get some hybrid vigour which makes for healthy and abundant plants. The only problem with this is that so many varieties of potato are poor berry setters, so not all varieties can be hybridised.

If you want to grow seeds from one specific variety it can be as simple as saving naturally pollinated berries from it, but if you want to be sure of getting self-pollinated seeds, it's easy enough to do (as long as it's one of the fertile varieties). Just dab a flower with pollen scraped from its own anthers, or other flowers on the same plant, or from other plants of the same variety. Bear in mind though that you will not get a true-breeding offspring of the parent variety by doing so. As potatoes are very heterozygous and have four lots of genetic material to throw around with cheerful abandon, even when they're self-pollinated they segregate into many different phenotypes. If you grow self-pollinated seed from Salad Blue, for example, you will not end up with a lot of spuds which look like Salad Blue. You will get varying shades of blue flesh, some much lighter than the original, some darker, and a few with pinky skin. If you grow selfed seeds from Congo, another blue variety, you may end up with a baffling range of purples, pinks and pure snowy whites, with considerable variation in tuber shape. What's happening is that all the genetic material which has been funnelled into the variety from various ancestors is segregating. Recessive traits emerge which weren't apparent in the variety you started with. If you grow enough self-pollinated offspring, you can start to build up a picture of the variety's pedigree, as many of the ancestral characteristics magically come back to life. So it can be a really fascinating thing to do.

Seedling from Salad Blue OP
A seedling grown from self-pollinated seed of Salad Blue. It's the only plant in the batch which has this striking black tinged foliage and black stems. I'm hoping it'll produce some dark tubers to go with it.

It's important to remember though that nature designed potatoes to be outbreeders, and if they self-pollinate they may show some degree of inbreeding depression. Only a bit though. As most spuds have such a rich and diverse genepool they can get away with a certain amount of inbreeding, but you may find self-pollinated seeds grow less vigorously than hybrids. That's not a problem and shouldn't put you off trying self-pollinated seed … but it's better to sow a few more than you need and then select the seedlings which show the most vigour and whoomph.

Variety differences
Differences in the fertility of individual varieties will most likely dictate what crosses you make, and how you do them. Over many years of being propagated by tubers, cultivated potatoes have moved away from the idea of flowering and producing seeds, and many of them can't be bothered to do it any more. Ironically for such a naturally variable and heterozygous plant, a historic lack of genetic diversity is thought to be the cause of the potato's fertility issues. The vast majority of modern cultivated potatoes are descended from one single Chilean spud, which had what is known as T-type cytoplasm, a genetic predisposition to making offspring with infertile pollen. Over the years many of these semi-infertile lines have been selected deliberately, as the male-sterility makes the process of hybridising them much easier. Consequently an awful lot of modern spuds have infertile pollen, and some are female-sterile too. Some can't be arsed to flower at all, and just dump their buds as soon as they appear. There are things you can do to force a reluctant variety to produce flowers, but it's a lot of hassle which I won't go into here, and from the point of view of future breeding work it makes more sense to choose varieties that at least show some willingness to come up with the goods.

I wish I could give a simple list of which variety does what, but I only know about the ones I've grown and observed myself, and it can vary from garden to garden anyway. Different countries have different varieties - import restrictions have affected exchange of material - so the ones I work with in the UK may not be available to people in the USA (just as most popular US varieties are strangers to me). So you will have to experiment with whatever you have available. As far as I can see, varieties fall roughly into four categories.

Some potatoes are very fertile and make excellent male or female parent varieties. Salad Blue is the Cassanova of the potato world - it only has to look at another potato and a berry starts swelling. You can usually tell a fertile variety because it naturally sets its own berries in profusion. Desirée is another very fertile one, and so is Mayan Gold, although the latter is a diploid so it needs to find the right kind of partner, or get lucky mating with a tetraploid.

Most cultivars fall into the male-sterile or almost-male-sterile category - these are the ones which flower happily enough but don't tend to set berries. Highland Burgundy Red is a good example of this, as is British Queen. It gamely produces a mass of dainty little flowers but in years of growing it I've never had a single berry. Give it a dab of pollen from a fertile variety though, and it sets berries very readily. So it makes an extremely good female parent. The advantage of male-sterile varieties is that you don't have to emasculate them, which makes it much quicker and easier to hand-pollinate them. Some varieties which appear to be male-sterile may actually be female-sterile. So it's worth trying the pollen on another variety to see if it will take. The disadvantage of using these partially sterile varieties is that it perpetuates the poor fertility of potatoes. If you want to do Solanum tuberosum a real favour in your breeding projects, select the progeny for good berry production. Because good berry production is what will keep its genetic heritage alive, as well as enabling some much needed new diversity to come in.

Then you have what you might call the awkward buggers category. These include Pink Fir Apple (syn. Rose Finn Apple) which not only has male sterility issues, it often can't be bothered to set a berry even when it's given fertile pollen. What usually happens is that the flower opens happily enough and you carefully pollinate it two or three times and on the third day the whole bloody thing drops off. Or worse, it starts to set a berry and then it falls off before it's mature. It pays to try again though, because there's a good chance that one of the pollinations will take eventually, when the plant is in the right mood and the planets are in the right alignment or there's an 'r' in the month. It's a pain in the backside to have to keep pollinating more flowers, but bearing in mind that each berry can easily produce 100 seeds or more, it only takes one successful pollination to give you loads of future breeding material - so it's worth persevering. Again, with a variety like this you don't need to waste time emasculating. I just go through the whole crop each day dabbing fertile pollen on every stigma I can find and saying "come on, set a bloody berry you sod!"

And finally you have the total refuseniks. There is a wonderful Victorian potato called Witch Hill which is reputed to be one of the best flavoured potatoes around - it is truly delicious. I would love to use it in breeding work. But every year the flower buds appear, and just as they're starting to look promising they drop off. All of them. Little dessicated posies cast to the ground. Now, unless it changes its mind, I cannot breed from it. If a variety won't flower, there is no breeding possibility, it's as simple as that. I could grow fields of the stuff and hope for a spontaneous somatic mutation, but that may never happen. Witch Hill is a genetic dead end. This is why breeders like Tom Wagner select breeding lines from varieties which are good berry setters. If a variety won't flower or won't set berries, it has no future.

The annoying thing is, Witch Hill did flower for me a couple of times when I first got it (it came to me as a laboratory-grown microplant) but I hadn't got into potato breeding at that time so I didn't think to make any crosses with it. D'oh!

Hybridising potatoes: the practical bit
Let's be grateful for small mercies: potato flowers are nice and simple and easy to work with. They are 'perfect' flowers which contain both male and female parts.

Anatomy of a potato flower
Anatomy of a potato flower. Each of the anthers is a double sac, both halves containing pollen. When the anthers mature they develop little holes in the ends (like a salt cellar) and the pollen falls out onto the stigma.

The Mayan Gold blossom shown above is fairly typical, but there are variety differences in the exact shape of the flower. Some have a long style where the stigma protrudes some way out of the flower (be aware that a sticky-outy stigma has more chance of being cross-pollinated by passing insects than one where the stigma is hidden away). Some produce a neat little fused anther cone, others produce a rather grotty collection of misshapen anthers which don't hold together properly. Some (like Pink Fir Apple) do weird things where anthers and petals morph into one another. None of this matters - the principle is the same. You'll get to know the individual character of the flowers in your own garden as you work with them.

In order to control what pollen fertilises the flower, you have to stop the flower from fertilising itself, so that means removing the male parts of the flower before they mature. As I explained above, with some varieties you don't need to do this - if the variety produces sterile pollen or none at all, you can save yourself the trouble. The instructions shown here are for if you have a fertile variety or want to be sure of getting hybrid rather than selfed seed.

Potato flowers are produced in cymes - bunches of flowers which open consecutively, 2 or 3 at a time. The flowers last two to four days but tend to close up in late afternoon. The anthers develop holes in their tips when they're ready to dehisce, though they're not very glamorous - in fact they look more like some insect has had a go at them. Potato pollen is white, powdery and very fine. The stigma is receptive for about 2 days and the period of pollen shedding also lasts about 2 days. Fortunately for the garden dabbler, the female part tends to become receptive just before the pollen starts to shed, so you have a window of opportunity to intervene.

The best time for hand-pollination is in the morning when pollen is most abundant, and when the temperature is fairly cool. But I wouldn't worry too much about this, it works at other times too.

If you're using a variety with infertile pollen, or you aren't bothered about the chance of a few self-pollinated seeds, you can skip steps 2 to 4.

Potato hand-pollination 1
Step 1: Having chosen the variety you want to use as the female parent, find a blossom at the right stage. Potato pollen can be shed quite early, before the flower opens, so emasculation has to be done while it's still at the bud stage. What you're looking for is a nearly-ready bud where the calyx (outer green bit) has started to open but the petals are still shut. This is a variety with a sticky-outy stigma, but with many varieties it will still be hidden inside the petals. Doesn't matter either way, although a sticky-outy like this inevitably carries a small risk of picking up stray pollen from elsewhere.

You may notice a strand of mauve wool poking out underneath. I tied this around the stem of the flower (or in this instance the whole cyme, as I'm going to hand-pollinate all of them) as a marker, so I can be sure I know which ones I've hand-pollinated. I use a different colour of wool to indicate different pollen fathers.

Potato hand-pollination 2
Step 2: Peel back the petals and you'll find the anthers inside. They are still immature at this stage - with no holes in the ends. If they do have holes and are shedding pollen, try a slightly younger bud instead!

Potato hand-pollination 3
Step 3: Using a blunt scalpel blade, tweezers or similar, pull/scrape the anthers off, being very careful not to damage the style - the central stalk with the stigma at the end.

Potato hand-pollination 4
Step 4: After removing all the anthers you're left with a denuded female part, ready to be pollinated with the pollen of your choice.

Potato hand-pollination 5
Step 5: Next find the flower you want to use as the male parent. Choose a blossom which is newly opened, as those are the ones most likely to have a good pollen stash (the ends of the anthers should be open at this stage). Pull off a single anther using tweezers/scalpel/fingers.

Potato hand-pollination 6
Step 6: When you turn the anther over you'll see it has a seam down the back, separating the two pollen sacs. Additionally, each individual sac has a little slit down its centre. Carefully slip the tip of a blunt scalpel blade through the slit and slide it along. Note that the slit should be open so you can insert the blade freely ... you want to avoid cutting into the anther if you can. 

If there is pollen inside, you will see it on the tip of the blade. It's a very fine white powder. If you don't see any white powder, try another anther from a different flower. You don't have to collect all the pollen at once ... just scrape out enough to dab on the female flower, and use the rest for more pollinations. (When the first sac is empty you can do the same with the other side. You can often pollinate ten or a dozen flowers from the pollen in a ripe anther like this.)

Potato hand-pollination 7
Step 7: Armed with your pollen-tipped scalpel, go back to the bud you just emasculated and dab the pollen powder onto the stigma - which is the knobbly-bobbly thing at the end. The stigma is mildly sticky when it's receptive, so you should find the pollen grains sticking to it quite readily. No need to make a song and dance with it - just a gentle dabbing so as not to risk damaging the stigma.

Potato hand-pollination 8
Step 8: The next day, go back to the same flower and pollinate it again with pollen from another fresh anther. The stigma remains receptive for around two days in total but you don't know exactly when that is, so for best results give it a pollen dab on three consecutive days. You'll notice that the petals have opened on this flower now, although it looks a bit weird as it has no anthers. Once the petals have closed and wilted a bit, you can assume it's no longer receptive.

Potato hand-pollination 9
Step 9: The berry starts to form. Yay!

From this point on, patience is the order of the day. Potato berries seem to mature painfully slowly. Try to resist the temptation to prod and poke them, you don't want them to fall off as they dangle clumsily on their alarmingly scrawny stalks. After about four weeks you need to watch for them dropping off naturally. Ideally, tie a little cloth or paper bag over them at this stage so that they are caught safely if they drop. Alternatively, be very vigilant, and ready to rummage about on the ground if you notice them suddenly go AWOL. Fortunately they don't taste nice enough for animals to be interested in them, at least not in the way of UK garden wildlife, so they're unlikely to be carried off, but you don't want to chance it.

One key factor about potato berries, significantly unlike tomatoes (to which they're closely related), is that the seeds carry on developing even after they've detached from the plant, and the berries will stay firm for months. This has several advantages. For one thing it takes the pressure off you to extract the seed from them ... you can leave them until you've got the time and inclination, even weeks or months down the line. Secondly it means that all is not lost if the berry is dropped too early or the plant dies prematurely. This is very significant in the light of the blight problems we are all besieged with. The plants can be struck down by blight, wither and rot - and the berries will still survive. Save the berries and let them mature, and as long as you clean them thoroughly they will yield perfectly healthy seed.

The topic of cleaning and processing TPS from the berries is to be the subject of a separate post. In the mean time, go out and make some berries!

With thanks to Tom Wagner and friends at the TaterMater forum for advice and suggestions (any errors are entirely my own responsibility).