Golden Sweet x Carruthers' Purple Podded F2. First one to flower.
Today has been a perfect day for hand-pollinating peas. Warm and dry but not too sunny - which creates just the right conditions for pollen to spill its abundance and for stigmatic goo to be in the right mood to receive it. Even more usefully, it was completely breezeless with not so much as a leaf blade stirring. The bitter lessons of trying to hand-pollinate flowers that are thrashing about in the wind, not to mention walking across the garden with a precious blob of pollen on the end of a scalpel, have taught me that pollinations on breezy days are the stuff of futility. All the more so for those of us with waist-length hair, which is guaranteed to flap across your face at the very moment you were trying to deposit a miniscule dab of pollen onto a particularly wobbly and elusive stigma.
As the weather was so perfect for it, I was really hoping to get some useful pollinations done for my red podded pea project. Only trouble is, most of the flowers I want aren't ready. The true red podders aren't even producing buds yet, and my semi-red mangetout line, which I'm hoping to cross with the Luna Trick sugarsnap for some peachy-red snap pods, didn't want to play either. I found a prime pollen-bearing bud on it that was well past the usual stage for self-fertilisation but when I cut it open I found it stubbornly refusing to dehisce.
An F4 plant from my semi-red podded mangetout line, currently struggling under the temporary working name of Peachy, getting ready for some blossom action (but not yet).
So instead I did some pollinations I didn't really need using the flowers I had available. It is worth pointing out that my beloved Luna Trick pea is the result of just such a casual union, in which I used up the last of some Sugar Ann flowers to pollinate a few buds of Golden Sweet just because I was bored. It turned out to be an inspired combination. Today's efforts mostly involved Sugar Snap flowers as females, pollinated with some of my purple F2 plants which may or may not turn out to be any good. I used the opportunity to take some close-up photographs of the pollination process. It's my fourth attempt to take such pictures. Thing is, you really need three hands for it, or an assistant who knows what they're doing. I have neither, so Plan B was to stick the camera on a tripod and use the self-timer for some very cumbersome hands-free photography, which resolved the three-hands issue but gave me some more challenges in trying to get it to focus in the right place when there's negligible depth of field. Anyway, if any of them are any good I'll add them to my previous pea-breeding tutorial.
The hand pollinations are just one aspect of what I'm doing on this crimson seeking project. Since my pièce de résistance in the red podded pea department stubbornly refused to yield me any fibre-free pods, I've been looking at alternative ways of getting them. Which now involves several simultaneous endeavours.
Growing out the rest of the F2 seed from whence the original came. This is the biggest hope. The particular combination of genes I need are a minority class which will only show up in a small proportion of the F2 offspring. I need the yellow pod gene (recessive), two purple pod genes (both dominant) and two fibre-thwarting genes (both recessive). I can't be arsed to look up in a Punnett Square what the actual chances are and calculate the number of plants I need for 95% probability … I'm content to know that it may take a lot of plants in order to deliver the holy grail. This year it's down to luck anyway, as I have only a small amount of F2 seed left and so I can't grow lots of plants. Even the seed I do have is of poor quality because it was grown from a late summer crop (I used to have this trick of growing two consecutive generations in one season to double the speed of my breeding work, but have since stopped doing it because the second crop yields weak seed at best, and at worst yields nothing and just wastes valuable breeding material). So I have about fifteen, maybe twenty plants, and they may or may not offer any red pods. The moment of truth is approaching, as the F2 plants have got flower buds.
They're very pretty buds, with the mauve blush that promises bicolour flowers. Both parent varieties had bicolour flowers, so I'm expecting to see it in all the offspring. The ones shown above are fairly typical and there are others similar, with more or less purple sploshing on the stems and leaves. But I can already categorically rule out any red pods from these two plants or any of the others currently budding. The reason? Green calyx.
Green calyx means green pods. I've noticed from my work with yellow podded peas that there is a direct correlation between the calyx colour and the pod colour. Yellow podded peas are always preceded by pale cream buds which turn into a cream calyx. Sometimes it has green mottling, and pink dapples, but the base colour is always cream. (Have a look at the picture of Peachy above and see how cream the calyx is compared to these F2 buds). I suspect the cream calyx/yellow pod may actually be coded by the same gene. If they are separate genes, they are certainly slapped together pretty tightly on the chromosome, and inherit together. It's not affected by flower colour - you can get white flowers or purple bicolour flowers on a yellow-podded pea, it's just the calyx and pod colour that are inseparable from each other.
When I say that green calyx means green pods, it may also mean purple pods … or partial purple. That's because purple podded peas are in fact green podded. I know that sounds weird, and I've had to explain it so many times on plant breeding forums it's obviously something a lot of people find hard to follow. If you look closely at a purple pod, the very tip where it attaches onto the plant is green. Break it open and it will be green inside. The purple pigment, no matter how intense it looks, is merely on the surface, and the base colour of the pod is green. This is also the reason why all purple podded peas turn green when cooked. The water-soluble anthocyanin pigment is just sitting on the surface and is washed away in hot water.
I admit it did take me a while to work this out. The first time I grew F2 seeds from this cross, it produced red, green, yellow and purple pods in varying proportions. I couldn't understand why a cross between a purple podder and a yellow podder yielded so many offspring with green pods. Neither of the parents appeared to have green pods so where did they come from? The simple answer is that the purple parent is green podded, with the green hidden under the layer of purple. In the great gene reshuffle, some of the offspring end up with green pods without the genes for purple overlay, and so they stay green.
The same principle applies to red pods. They are simply yellow-podded peas with a purple overlay, which combines visually to make deep red. It's not possible to have red pods unless the base colour of the pod is yellow. That's how I know the two buds shown above are not going to give me red pods. A red-podder bud will invariably have a cream calyx, not a green one.
While I shouldn't condone the practice of peeking inside unopened leaf clusters to look at bud colours, I naturally can't resist it. And it's been very encouraging. Because two of the upcoming F2 plants which are not ready to blossom yet are showing cream buds among distinctly yellowy foliage. Even when they're tiny, the cream colour is unmistakable. The cream buds don't necessarily result in red pods, some will just stay yellow, it depends whether the genes for purple overlay are also present. But they do open up the likelihood of it. Also, one of the cream buds is showing a speck of pink colour on the calyx. While I don't have a genetic explanation for it, I have noticed a strong correlation between pink markings on the calyx and red pods. So I'm feeling lucky with this one.
Maybe it's not very clear in this photo, but this developing bud has a cream calyx - ergo yellow pods. Also a tiny pink spot on the calyx which is a good sign.
It's still pot luck whether any of the plants in this small sample will give me exactly what I want, but the solution is in there if only I can grow enough F2 plants. Which brings me on to my convenient back-up plan …
Growing out more F1 plants to make new F2 seed. I still have a number of F1 seeds saved from when I made the original cross. The seeds are good, healthy mature ones too. I started off a batch of about ten F1 plants this year. The beauty of peas and their efficient self-pollination is that you don't need to do anything except grow the F1 plants and save seed from them. They are veritable F2 seed machines. Every pea they produce has a unique individual genome, its own personal reshuffling of all those genetic goodies. Somewhere among the reshuffles is bound to be the specific five-gene combination I'm looking for.
F1 hybrid of Golden Sweet x Carruthers' Purple Podded. Flowering like billy-o and hopefully making lots of nice F2 seeds for me.
What's interesting about these F1 plants is that they are showing massive hybrid vigour, or heterosis. It's a phenomenon brought about by having a mixed up genome, a by-product of heterozygosity. Its cause has always been something of a mystery, though I'm told that some recent research has put it down to an enhanced ability for photosynthesis. Whatever the reason for it, my own observation is that it only happens in certain crosses - though there are degrees of it. And it's for one generation only - you don't tend to see it in F2 plants. This has been especially marked in my current crop, because I sowed the F1 and F2 seeds from the same cross side by side in the same rootrainer tray, and they are now growing side by side out in the garden. And from the moment of germination, the F1 plants rocketed away from their F2 nephews. They grew faster, had thicker stems, established themselves in the outdoors quicker, produced substantially bigger leaves and grew taller. They were also earlier to flower - and still having a burst of surplus energy to get shot of, have thrown out a lot of sideshoots too. Pea sideshoots are usually feeble, spindly things, if they ever get going at all. These are nothing of the sort. They are full-size, chunky, vigorous new branches which look set to flower and make pods.
Something else peculiar about the F1 plants, or one of them at least. I've been writing about the leaf aberrations in my peas this year, which I'm beginning to conclude are probably weather related. I mentioned the fasciation (thickening of the stem) in one of my other hybrids, despite the fact that it's a trait caused by recessive genes. Well, now some spontaneous fasciation has occurred in one of these F1 plants. To my knowledge, there are no fasciation genes in this hybrid, which is not related to the other one - they are completely separate breeding lines. Which leads me to assume that pea fasciation is not solely genetic, and can arise as an environmental reaction. What's even more weird is that the plant in question managed to unfasciate itself by splitting into two stems. A single stem with a well developed sideshoot is one thing, but this is a pair of twin stems growing at the same rate in different directions, equal and opposite.
This F1 pea developed spontaneous fasciation (stem widening) and then split into two separate but equal growing tips. This is not normal for peas!
Edit: I've just done some homework on fasciation, following a link from Rhizowen's wonderful blog, and it seems that spontaneous fasciation from environmental stress is a well known phenomenon - actually more common than genetic fasciation. It's caused by damage to the growing tip by virus, bacteria, insect nibbling or frost - and a reversion back to normal growth is also common. In this case, frost is almost certainly the culprit.
Other avenues. I had just eight seeds left from my original red podded pea. I sowed them, and three fell victim to marauding gastropods. The five survivors are doing well though, and although there will be no edible pods among them, they will enable me to make some crosses. The priority will be to cross them with my two Luna Trick lines, which are genetically similar, being derived from the same original parent variety, but represent a superior form of it with good-flavoured and fully edible yellow pods. Another batch of twenty or so are on the go, thanks to my big haired friend Graham, who grew some last year and gave me back some seeds from the best of them. Again, they won't have edible pods, but they will be priceless for making crosses and might also make the basis for a red-podded shelling pea. Also of course there's the Peachy line which has edible pods which are part-red. That might turn into a variety in its own right, and will certainly be useful for making crosses with the pure red (if it ever gives me any pollen).
Monday, 31 May 2010
Posted by Rebsie Fairholm at 11:59 pm
Saturday, 29 May 2010
I never got round to blogging about last year's tomato crop, so here is a very brief summary of it before this year's crop reaches the point where I have to blog about that instead. I didn't grow very much last year, so here are the three best ones. Bottle tops are included for scale.
Essex Wonder - I got this one from the Heritage Seed Library, mainly for sentimental reasons. I grew up in north Essex which has (or had) an extensive market gardening and glasshouse industry. Essex Wonder was a popular market gardener's tomato from the 1930s to 1950s, extensively grown in the area before dropping from the catalogues and fading to near-extinction. I found it to be a very pleasant if rather "normal" tomato compared to the weird freakish stuff I usually grow. The fruits are almost perfectly spherical and bright red and come in a range of sizes from mini-cherry to golf ball, all with a pretty decent flavour.
OSU Blue Fruit
OSU Blue Fruit - oh this is special! Bred by Jim Myers at Oregon State University in the US, it's a dark anthocyanin-skinned purple tomato which, given enough direct sunlight, turns coal black when it's ripe. At the moment it isn't available commercially (as far as I know); they're working on improving its flavour and shape, and this prototype is doing the rounds among curious collectors and amateur breeders. I got mine from Michael Johnson in Nottingham.
The fruits are only purple/black on the outside. Cut them open and they are red. They also stay red - or a deep bronzy red-black - on any part that doesn't get full sun, because they need strong light to develop their colour. That includes the area underneath the calyx at the top of the fruit, so they have a little red star on the top when you harvest them. They are supposedly more reliable at developing the full colour when grown outdoors, but I grew mine in the greenhouse and they came up a treat.
As with many exciting plant breeding developments, the mechanism behind the blue fruit is relatively straightforward. There are three wild species of tomato which contain some anthocyanin pigment in the fruit, each involving a different gene. Two are dominant: Abg comes from Solanum lycopersicoides while Aft is found in Solanum chilense, and the recessive atv comes from Solanum cheesemanii. All of these genes have already been bred into cultivated tomatoes over the years, without producing fully blue fruits. What the OSU team discovered was that if you combine all three of these genes together you get a cumulative effect which intensifies the pigment. Voilà blue fruit.
The downside of OSU Blue Fruit is said to be its flavour, which has a reputation for being "inky". Anthocyanins are normally tasteless, but they're often accompanied by other compounds and biochemical changes which can affect the flavour. Consequently I wasn't expecting that much from it in the way of taste. But I was pleasantly surprised - it was actually pretty palatable. I'd be lying if I said it was up there with the best tasting tomatoes, but it certainly wasn't poor either … it was as good as or better than most of what you'd find in the supermarket.
Pugliese Green - this Italian variety was given to me by Jeremy Cherfas over at Agricultural Biodiversity. Despite the name, it's very much a red tomato, and doesn't look significantly different from other red tomatoes, though it has a certain intensity of colour. There is one thing that makes it stand out though - the flavour is stupendously good. I'm even able to nibble at it raw (see below). It's fruity and juicy and succulent with just the right balance of gel and flesh, and will probably become a flavour benchmark for me. Thank you Jeremy.
That was last year's crop. Meanwhile the 2010 crop is going nuts in the greenhouse making the most of the unlikely sunny weather. Here's what I've got crammed in there …
OSU Blue Fruit
Darby Striped Pink/Yellow
Darby Striped Red/Green
Pink Freud F3 (one of my own experiments)
Banana Legs x Green Tiger F1 (another bit of hand-pollinated jiggery pokery)
The horrendous affliction of late blight means that it's no longer practical to grow tomatoes anywhere but inside the greenhouse, where they're sheltered from the warm summer rain which brings the deadly spores to the garden. Normally it's not worth trying to grow any outdoor tomatoes any more, but Patrick kindly sent me some seeds of Tomatito de Jalapa, which is supposed to be blight resistant. There are genes for blight resistence in certain wild species of tomato, and some of these are being bred into garden varieties. From what I gather, this has been working OK with small cherry tomatoes but is not much cop when it comes to the big-fruited types. So if you want blight resistance you have to have tiddly little fruits. Which is fine by me, I don't mind. I have little knowledge of what Tomatito de Jalapa is like or how assiduously it fends off blight, but I'm looking forward to experimenting with it. The greenhouse is full, but the beauty of this one is that I can grow it outdoors.
Tomatito de Jalapa seedlings, as photographed a couple of weeks ago. They have since been potted up individually and are growing like rockets.
I've also got another tomato that I pinched from a restaurant. I don't know what variety it is, but I had to have it. At this point I need to confess something. I actually hate raw tomatoes, and can't eat them unless they're mixed with something else. I love them cooked, and I love growing them, but when it comes to snacking them off the vine - forget it. They actually make me gag. But a couple of months ago I was in a little basement restaurant in Cheltenham called Café Rubik, which does very nice food. The curse of being vegetarian though is that everything you order always comes with salad. Chefs seem to assume that all vegetarians are health freaks and don't want to eat chips or anything stodgy and interesting, so if you're vegetarian simply because you don't want to eat dead animals but do want to eat stodgy interesting and unhealthy stuff without dead animals in, you're out of luck. So, confronted with the mandatory pile of bleak greenery, I was thinking "fuck, how am I going to get through all these raw tomatoes?" But when I nibbled the edge of one I was surprised to find it rather fruity. I nibbled a bit more. It didn't taste of tomatoes at all, it was like a tangy little fruit - a cape gooseberry or something. I then astounded myself by eating a whole one, and actually enjoyed it. This really was a momentous event because I've never eaten a raw tomato like that before. It was unprecedented.
Well obviously there's only one thing you can do in those circumstances, and that's steal one to take home and get the seeds out of it. I waited some while for a moment when the waiter wasn't looking, but he seemed to be looking all the time, so in the end I just grabbed one and shoved it in my pocket. He looked a bit surprised but didn't say anything. I took it home and fermented the gel and got quite a few seeds from it. Although received wisdom has it that tomatoes need to over-ripen to the point of inedibility in order to produce mature seed, I've always had perfectly good results saving seeds from eating-stage tomatoes, and indeed other vegetables. If you like the taste of it scrape some seeds out of it, that's my motto.
The original Café Rubik tomato, as pilfered.
Sure enough the seeds germinated rampantly and have grown into very healthy plants. They all look the same so far too, which is a good sign, as it implies that it's a true-breeding open pollinated variety and not a hybrid. I've no idea what variety it is, though presumably it does have a real name. It might even be a well known mainstream commercial variety for all I know. But I've called it Café Rubik in lieu of an identification. Not much to tell from its outer appearance … it's round, and red, and tomatoish. I'll post pictures of the plants as they grow in case anybody recognises it.
Posted by Rebsie Fairholm at 10:24 pm
Wednesday, 19 May 2010
Well it was only a few days ago that I blogged about the likely genetic expression in my Alderman x Salmon-Flowered F1 pea. And already the plants are thumbing their noses at me and proving me wrong.
Let me begin my explanation by showing you a picture of their dad.
Salmon-Flowered pea growing in my garden in 2007. This is an umbellatum type pea which bears all its flowers in a clump at the top. This happens because the new stems formed at each successive leaf node fuse together and are drawn upwards into a big fat monster stem, for which the technical word is fasciation.
I mentioned that fasciation is caused by a very particular combination of three recessive genes. Because they're recessive, and they need to present themselves all together in order to do their thing, I wasn't expecting to see any sign of fasciation in the F1. I thought they would be masked by the dominant alleles of Alderman. Shows how much I bloody know about it.
Young Alderman x Salmon-Flowered F1 plant showing early but unmistakable signs of stem fasciation. In other words, it's going to be an umbellatum phenotype with a clumpy flower posy at the top.
I don't know why this is happening - I was expecting the growth habit to be more in keeping with the hybrid's mum, Alderman. Multiple-recessives do have interesting effects, but you see that in the F2 plants, not the F1. What's most odd is that I have some young Salmon-Flowered plants on the go at the moment and they are not yet showing anywhere near as much fasciation as this. Perhaps Alderman has one or more of the recessive fasciation genes hidden unexpressed in its DNA. Perhaps the recessives don't have an equivalent dominant allele and are able to express themselves freely. I haven't got a clue (suggestions welcome) so I'm just speculating. At any rate it's showing itself consistently in all the F1 plants.
Alderman x Salmon-Flowered F1. The leaf stems have divided and doubled themselves, a feature of umbellatum peas.
Meanwhile though, I'm seeing some leaf aberrations in my other peas too, and those are even more devoid of an explanation. It takes many forms and it's mostly happening among my hybrids, but not exclusively. I've no idea what causes these effects. Cold weather? Virus? Genetic mismatch? Mystical cosmic rays?
Pea leaves usually come in pairs, but here is a gallery of weirdness.
Trefoil. Golden Sweet x Kent Blue F1.
Quatrefoil. Magnum Bonum x Carruthers' Purple Podded F2.
Another quatrefoil. This one is bearing one of its leaves upside down, and has two sets of tendrils, one on each side. Golden Sweet x Carruthers' Purple Podded F2.
Quatrefoil at the main node, creating a butterfly effect. Red-podded pea (Golden Sweet x Carruthers' Purple Podded F5).
Magnum Bonum x Carruthers' Purple Podded F2. This hybrid is the one that is showing by far the most leaf weirdness, with a number of the plants showing what I can only describe as a "cabbaging" effect … with surplus leaf growth bunching up around the growing tip, and sometimes even terminating the tip in a leaf-and-tendril dead end. But curiously, it is only affecting the plants that were grown from light-coloured (cream or green) seeds. I sowed the dark coloured seeds separately in the same tray and those are all normal.
May Queen, an old English variety, with two leaf nodes fused together. Each node has a fully formed pair of leaves and a single flowering stem, but all squashed up together.
At least I haven't suffered any losses (yet) in the recent spell of unseasonal frost, except for a pot of bush basil which 'melted' overnight when the temperature got too low for it. Apart from that, I've been lucky - thanks to Cheltenham's sheltered climate and my garden being hemmed in by trees and houses. Garden pests have been taking their toll though. After an abnormally dry spring which kept the slugs and snails in hibernation for weeks longer than normal, a few days of heavy rain brought them all out and they were ravenously hungry. The Luna Trick F4 crop suffered some quite severe damage, with about a quarter of the plants gnawed down to stumps within 48 hours. The damaged ones will make new shoots, but it will set them back by several weeks. Sluggy bastards. I even had a potato haulm completely devoured in the space of two nights - gone and vanished without trace. The culprits for this damage tend to be either the large brown garden snails or the tiny keel slugs who live in the soil and are barely noticed at the crime scene.
The other garden pest damaging my peas at the moment is a ginger cat with a big arse. It's a funny thing about cat social mentality - he wants attention and doesn't care whether it's positive or negative as long as he's getting it. He enjoys cuddles but is really just as happy when I'm yelling and chasing him off with a broom. Since he discovered he can get lots of noises and arm-waving from me by crashing over onto my pea seedlings, he's taken to doing it repeatedly. And the more I go "aaaargh!" the more he does it. I'm trying to reverse-condition him by walking away and ignoring him, but it's easier said than done … when someone slaps their capacious backside down on baby F4 plants that represent four years' breeding work, sometimes you just have to leap around and shout.
The Arse of Doom
Posted by Rebsie Fairholm at 11:56 pm
Friday, 14 May 2010
I thought I'd put up some pictures of the F1 hybrid peas I've got going, even though they don't look all that exciting at the moment. They aren't flowering yet but this is a good time to admire their axillary pigmentation.
I don't read up as much as I should on pea genetics, but it certainly seems that the genes controlling the expression of colour in different parts of the plant tend to come as a package deal. From what I have bothered to read, I know that there are distinct and separate genes for pink splodges in the leaf axil, for purple or pink bicolour flowers, purple seedcoat speckles and purple pods - plus another gene which switches colour production on or off for the whole plant. The purple pod genes (there's actually two of those) are often inherited separately, but the rest seem always to go together. It's quite useful in some ways, because the axil splodge enables me to predict flower colour several weeks before they flower, or even to select for flower colour before I sow by going for the dark-coloured or speckled seeds. Although they're different genes they are presumably all squidged right up together on the same chromosome.
The axillary splodges are made by just one major gene, but there is a lot of subtle variation in how they are expressed.
Golden Sweet x Kent Blue F1
I made this hybrid in 2007 and the seeds have been sitting around ever since waiting for me to do something with them. The plants have a very intense blotch in the leaf axil, with a distinctively purple hue.
I'm not sure what I'm expecting to get from this hybrid, it's one of my suck-it-and-see crosses. Both parents are heritage varieties of some considerable vintage, which usually makes for interesting hybrids. Certain traits can be predicted in the F1: Golden Sweet is yellow podded, but there is no trace of yellow colouring in these F1 plants because it's a recessive trait and will be hiding for now. I expect to see yellow pods in a quarter of the F2 offspring next year, but not in these. Bicolour purple flowers are pretty much a certainty though, as both parent varieties have them. But Kent Blue has the unusual feature of changing its flower colour. The flowers open as normal mauve and maroon bicolours, but within a day or so they change to a sky blue and midnight blue bicolour. They also have very pronounced veining on the back of the petals, which is very pretty. Whether these traits will show up in the F1 flowers remains to be seen. I'm also curious to see what happens to the pods in terms of width and knobbliness. Both parents are edible podded varieties of a slightly primitive type (i.e. not as sleek and fibre-free as a modern cultivar). There are two recessive genes responsible for edible pods and the way they interact is quite crucial. Depending on which ones I have here, the hybrid may be completely fibre-free (better than either parent) or they might be totally inedible. It may seem strange that you can cross two edible-podded varieties together and end up with inedible pods, but it does happen (and has happened to me!) It's one of the endearing little quirks you get in a multi-factor cross with recessive genes.
Golden Sweet x Carruthers' Purple Podded F1
This hybrid is the parent of my red-podded pea. The red pods showed up in a small proportion of the F2 seeds, and so I'm growing another batch of F1 plants in order to produce more F2 seed, in the hope of getting some red edible podded recombos. These plants are from the original batch of seeds from the cross I made in 2007, and despite the seed being three years old they are showing considerable hybrid vigour, overtaking all the other peas in the garden.
The axillary pigmentation is very flamboyant, forming two distinct pinky-red rings with a white band in the middle, and something of a Bowie lightning flash at the top. This is an exaggerated form of the double axil ring inherited from Golden Sweet.
As I've already grown some of these F1 seeds I know what to expect from them, but a lot of it is easy to predict anyway. Both parents have purple flowers, which are dominant, so the F1 will have them too. Both parents are tall, and that's also dominant. Carruthers' Purple Podded passes on the two dominant genes for purple pods, so the F1 hybrid will have purple pods. Golden Sweet contributes the yellow-pod gene, but that's recessive, so none in the F1 generation. It's when these genes segregate out in the F2 that things get exciting, because when the two purple pod genes happen to come together with the yellow pod gene, that's the magic formula that gives red pods.
Alderman x Salmon-Flowered F1
Another 2007 hybrid which has sat in a box and never been grown before. This one is a cross between one of the best heritage shelling peas and a botanical curiosity, so it is venturing into uncharted territory. See how subdued the axil colour is on this one. It's a soft muted pink and sits tightly within the axil without spreading out into the leaf. The upper stem and tendrils have a rosy blush too, and the leaves have red edges. These traits are all inherited from dad, Salmon-Flowered. There are no obvious colour genes in Alderman, though it may have some unexpressed ones lurking in its genome waiting to burst forth in an unexpected carnival. On the surface it's a fairly normal green-podded pea, chosen for its excellent flavour.
What makes Salmon-Flowered such a curiosity is that it's an umbellatum type pea. These were popular in past centuries, once known as crown peas, but they are now rare. Instead of producing flowers and pods up the length of the stem, they bear all their bounty in a whopping great clump at the top. They look so different from normal peas that they were formerly classified as a separate species, Pisum umbellatum. This has now been dropped, however, since it was discovered that they are botanically the same as other domestic peas and their bizarre form is merely the result of a combination of three recessive genes, whose exact function and interaction is still not fully understood.
Well I don't understand them either, but as they are all recessive I can probably assume that none of the umbellatum traits will be apparent in an F1 hybrid. Even in the F2, it may be a very small minority class (where all three recessives combine). Never mind, there is other excitement to discover. Such as flower colour. Alderman is a white-flowered pea, and white flowers are recessive. Salmon-Flowered is ... er ... salmon flowered (two-tone pale pink and salmon pink) which I believe is also recessive. What happens when I cross these two shrinking violets? God knows. I'll have to wait and see. They may be pink, they may be white - or they may be neither. As I said above, a multi-factor cross with recessive genes can throw up surprising and counterintuitive results. I'm looking forward to seeing what turns up.
Posted by Rebsie Fairholm at 5:51 pm
Friday, 7 May 2010
Always looking to explore unusual heritage varieties and seek out material for breeding experiments, I was pleased to see that AlanRomans.com were stocking minitubers (that is, small laboratory-grown seed potatoes) of an old and hard to find blue potato called Congo. I'm interested in Congo because it's blue-fleshed - blue all the way through - and I have a strong interest in vegetables that bear this colour pigment because of its nutritional benefits as well as its glorious beauty. As well as being historically interesting and quirky, Congo has a reputation for being a good berry setter. That would make it an excellent variety to experiment with in breeding work, because it would ensure a good supply of TPS. I could have some real fun crossing it with other varieties, but also growing out its own self-pollinated TPS, which would in itself yield some interesting segregation for different traits (if you've read my article about TPS below, you'll know that the tetraploid arrangement of the potato genome gives it something of the nature of a genetic fruit machine).
So I ordered a pack of five Congo minitubers - not the kind of quantity that would give a good yield for the dinner table, but plenty enough to get the variety established in my garden and see what it has to offer. When my order arrived a couple of days later it contained not one minituber pack but two. The handwritten note explained that they only had 15mm-ish tubers left in stock rather than the 20mm-ish ones they preferred to supply, and so they sent me 6 rather than the 5 I ordered. Additionally, they sent me a pack of 5 minitubers of another rare and special variety, Red Craigs Royal, as a freebie. The Red Craigs Royal tubers had already started to chit and were at a stage where they really needed to be planted. This is really good customer service - it's a great way to keep people like me happy, because I get to add another precious heritage spud to my inventory and ensures that I will want to order from them again next time, and it shows that their attitude to heritage varieties is well motivated, in that they would rather give unsold stock to a good home.
As far as I'm aware, nobody in the UK is doing more than Alan Romans in conserving and promoting heritage potatoes. You may have seen these varieties making an appearance in Thompson & Morgan's catalogue, and in Waitrose - but all that is down to him. And it's not a simple case of reintroducing them on a whim either ... the laws and regulations relating to the sale of seed potatoes (and culinary ones) are complex and restrictive, and he's had a heck of a lot of bureaucracy to struggle against. It wouldn't be legal to sell field-grown potatoes to gardeners without an expensive process of certification, and minitubers are his latest solution to this obstacle. They are produced in a laboratory environment from disease-free plants held in vitro. Although they are small, they can be grown on and will soon build up a decent yield. The sterile environment in which they're produced may make them a little vulnerable when you plant them in the unfettered ravages of the soil, but they seem to cope and I've managed to grow laboratory-raised plants under organic conditions without too many problems. The bottom line is, if it wasn't for the laboratory process these rare and interesting varieties simply wouldn't be available at all.
Red Craigs Royal minitubers. The original Craigs Royal was introduced in 1947, bred in Scotland from a cross of Craigs Defiance x Gladstone. This red-skinned sport appeared in Perthshire in 1957 and quickly became extremely popular for its good yields and excellent flavour - only to be plunged into obscurity a few years later as the market moved on to other things. It's a second early type with a floury texture. As for its usefulness in my breeding projects, well, I'm not sure what to expect because the European Cultivated Potato Database lists it as a poor producer of berries but also as having high fertility pollen.
Congo minitubers. They don't look very exciting at the moment, but they are full of potential. There is a degree of confusion over this variety because there are two Congos. This blue-fleshed one is of British origin, thought possibly to have been created by a shepherd in the Scottish borders in the late 19th century. The other Congo is from Sweden and has white flesh (edit - or maybe not!). As if that wasn't confusing enough, there are suggestions that the blue version has many synonyms and may be known around the world as All Blue, British Columbia Blue, Russian Blue, Himalayan Black and McIntosh Black, amongst others - though they may be variants rather than identical clones. Congo is a very late maturing variety - so here's hoping the blight pestilence will be merciful.
Posted by Rebsie Fairholm at 5:24 pm