The climate in the UK is bonkers at the moment. Within the last fortnight we had a frost which had me scrabbling to protect all my tender plants. Now we have a record-breaking heatwave, with temperatures well over 30° … extreme and abnormal for May. Aside from being an alarming sign of how the climate emergency is accelerating, for my pink-flowered pea project it couldn't have come at a worse time.
Peas are a cool season crop. They can't deal with intense heat from the sun. If temperatures are too high, they struggle to flower and set pods. If they're exposed to full-on hot sun, their delicately watery leaves just dry up and shrivel. Normally the British spring weather is ideal for them, but this year they have been hit by conditions they can't deal with, right at the time they started flowering!
Above is the very first flower from this batch, which opened the day before the heatwave hit.
24 hours later, many of the plants looked like this:
Yes, that is a flowering top full of newly formed buds, dried out and burned to a crisp.
Damage like this is woeful for any gardener trying to get a crop of peas, but when it's a breeding project where the seeds are irreplaceable, it's potentially calamitous. I sowed almost all of the seeds I had available, so if this crop doesn't produce seed then I'm stuffed.
I do still have a couple of spare metres of Thermacrop fabric, so I chucked that over the top of the pea frame to screen a little of the sunlight off the plants. And it seems to be working. Thermacrop is designed to do the opposite of this, keeping plants warm. But in this instance it seems to work for keeping them cool, giving them dappled sunlight rather than an intense blast, and allowing air flow through so the heat doesn't build up underneath. Many plants are already damaged but this is at least stopping it from getting any worse.
The damaged plants are gamely still opening their blossoms where they can, and those which are more severely affected should be able to produce new shoots and have another go. So fingers crossed this is a setback rather than a disaster.
Let's have a recap on this project. It started way back in 2007 when I made a cross between Alderman, my favourite tall white-flowered garden pea with outstanding flavour, and a strange little pink-flowered umbellatum-type pea which came from the Heritage Seed Library under the generic name Salmon Flowered, but which resembles a Swedish heirloom called Rosakrone. Umbellatum or crown peas, once thought to be a different species because they look so different, are the result of a combination of recessive genes which cause fasciation, or stem-thickening, leading to all the flowers and pods being produced together in a clump at the top. Now very rare, they used to be popular in the 17th century before modern pea types superseded them. The aim of this project is to create something with all the garden and culinary qualities of Alderman, but with those beautiful pink blossoms.
For various reasons it took until 2019 for me to grow out the F2 seeds from this project (see
this post for the write-up) but it was broadly successful and from 16 plants I got 4 plants with the recessive pink flower trait – a perfect Mendelian ratio, no less. One of them was lost to a weather-related accident, but the other three produced seeds for the F3 generation. And those were what I sowed this year.
Here they are, newly sprouted back in March.
Ignore for now the two rows on the right hand side. These are growing alongside the others but are from a separate project, a cross between Sugar Snap and Salmon Flowered which are still at the F2 stage and will be covered in a separate post. The four rows on the left are what we're talking about here.
The first two rows are seeds from a plant numbered ASF 06, which was the best of the F2 plants in 2019. This plant produced seeds with a lot of diversity, including some which were wrinkled and some which were smoother with dimples. I've sowed one row of each, marked with W for wrinkled and D for dimpled. I thought it would be interesting to sow these separately, since wrinkled seeds are associated with higher sugar content and sweeter flavour. 16 seeds altogether from this parent plant, of which 15 germinated. Next we have 8 seeds from plant ASF 03, and 8 from ASF 15. These all germinated, so that gives me a total of 31 plants for my F3 generation. I'm pretty chuffed that most of them did germinate, given that the seeds had been left in a box for seven years.
Fast forward two months, and all of the above plants are starting to flower. There are some which are earlier than others, but there's only really a few days between them, so the flowering times are showing more uniformity than they did at the F2 stage.
Now, this project potentially has two recessive traits which I would like to get rid of. One is the umbellatum trait which has all the flowers clustering in a single bunch. I really don't want this, because it reduces yield and makes the plants top heavy and liable to fall over. The other is the gene which causes white flowers. As regular readers will know, there isn't a gene for white flowers as such, there's simply a gene which switches off all pigment production in the plant, of which white flowers are the consequence. This too I need to eliminate, because the whole point is to have pink flowers. If I'd been really lucky, I might have found one or more of these breeding lines not carrying either of the unwanted recessives. Sadly, both traits are indeed showing up in the F3 crop. Arse.
The umbellatum clump-top trait is complicated, and to the best of my knowledge involves three recessive genes. I don't know much about how they work, or whether all three of them are needed in order for the umbellatum trait to be expressed. Maybe they will only have two and will express partially, or maybe all three genes are lurking in the genome and will randomly appear in subsequent generations on the occasions when all three align. That scenario would make the umbellatum types relatively rare, but make it hard to eliminate them altogether. In this F3 crop only one plant is expressing it, and that's one of the offspring from ASF 03.
It is very pretty, and the flowers are pink, but this one unfortunately won't be contributing further to the Pink Flower project, because we don't want any more of these recessive genes thank you very much.
The white flower gene is much more straightforward. One recessive gene, with one simple function. Easy to spot and easy to weed out. Except that in the F3 plants so far, it's not inheriting in quite the way I expected.
It's still early days and not everything is in flower yet, but the presence or absence of a pink splodge in the leaf axils is a reliable indication of flower colour, so I'm able to predict what the colours will be. All three of the F3 breeding lines are producing some white flowers, so obviously all three of them have this unwanted recessive. Given the simplicity of the gene and past experience of working with it, I would expect an average of one in four of these plants to have white flowers. But the ratios are looking like this.
ASF 06 – 7 pinks and 8 whites
ASF 03 – 6 pinks and 2 whites
ASF 15 – 4 pinks and 4 whites
Hmm. We have a normal Mendelian ratio on ASF 03, but the others are looking more 50/50 pinks and whites.
A couple of caveats. One is that they aren't all in flower yet, and it's always possible that I've misidentified the colours until I actually see them bloom. The other is that this is a very small sample size and they won't necessarily make the expected ratios in such a small quantity of plants. This is probably the most likely explanation, i.e. it's nothing more than luck of the draw that I've ended up with fewer pinks than anticipated.
It's a minor frustration inherent in plant breeding. But on the plus side, I get to eat the white ones. Nom nom.
As I said, it's early days with this crop, and I now have the fun (but hard work) bit to look forward to: making notes and observations on every individual plant as they develop. I am pleased to say that nearly all the plants are showing good vigour and have grown to 5 or 6ft tall. This might be hybrid vigour from the cross of two very diverse original parents, or it might just be that they've all inherited the gene for tallness, which is dominant.
The plant which is looking to be the most interesting so far is ASF 06 / 01. Very vigorous and strong, it has lovely big pink splodges in the leaf axils and is also producing very developed sideshoots. It's too early to say whether the sideshoots will develop fully and actually produce flowers and pods, which is a relatively rare thing in peas, but they do look as though they might. This plant is also at the moment showing a very intriguing flower colour. Instead of the two-tone pink which others have, this one has a more uniform apricot pink which I've never seen before. I was quite excited when it first appeared, but knowing how environmental factors can impact the pigments in pea flowers, it may well just be a byproduct of the heat damage. As you can see in the photos below, this plant did suffer a bit while the buds were forming and so this colour may not be representative!
On the other hand, if the flowers do stay this colour I will be well chuffed! I've never seen this apricot shade in peas before, and it's lovely.
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