Sorry for not posting anything about plant breeding lately. I’ve been rather busy this year. But i still have a few plant breeding projects (mostly from last year) that i dedicated garden space this year for. These include my Colorado bred / adapted Watermelon Landrace, which did quite well last year (even a racoon thought so and ate one that was overripe). My Wild Pueblo squash from Utah. An attempt at a sweet potato growing / breeding project. A mass tomato growout / trial. Some perennial teosinte-maize hybrids. And my various pea variety growouts which includes: Salmon-flowered pea and crosses, mummy-white and crosses, mummy-pea, Biskopens and hoped crosses, Joseph’s red-podded peas, Joseph’s yellow podded peas, Orange-pod, Virescens Mutante, Sugar Magnolia, Sugaree, Green Beauty, Purple Passion, Dwarf Grey Sugar, Spring Rose, Canoe, Mighty Midget. I also finally made one successful cross this year between Mighty Midget and Purple Passion. That should eventually give me a super dwarf with purple seeds and also improve purple passion to have stronger stems as it’s normally a very spindly plant.
This winter, i think in February i experimented with making a small cold-frame and using it to plant some of my peas super early. You can see it here where i watered it with snow and then a few weeks later the pea seedlings emerging but it still being rather cold outside. It worked great though. This particular cold frame is more suited for super dwarf or extra dwarf peas or lettuce or something. If i had a greenhouse i’d totally experiment more with growing vegetables in the winter.
A nice segregating yellow pod from the red-podded breeding line. Very nice.
A nice yellow and red mottled pea pod. The contrast is what makes this one really stand out! A line to keep an eye on for sure.
A remnant from Dan Quickert’s purple snow pea project. This is one of the few that didn’t die off a few years back, so this one must have had much better genetics than it’s siblings. A nice example of a purple snow pea, which are still quite rare. This one is called ‘Midnight Snow’.
And some of the orange-pod gene peas (orp) i’m growing from the Gatersleben gene bank. These have an interesting orange color on the inside of the pod. I hope to use these to make better yellows and better red podded peas in the future.
Pea Breeding is actually really awesome. Especially when you can get really neat colors to recombine into new combinations. Punnet Squares to predict the genetics of pea breeding is also very helpful and fun too. This page contains a multitude of information on pea genetics.
(This page was originally hosted on my test website Biolumo.com, but since i am hosting it myself on my own computer it is not exactly a reliable place, and hence i have copied all of the relevant information here to my blog as a permanent place to find it.)
The following pea breeding illustrations were obtained from the Eighth Edition of Biology by Neil A. Campbell. I’ve scanned the relevant illustrations about pea breeding. If you would like to view the genetics section in PDF form instead, then here you go: You can read the whole genetics chapter in a virtual pdf online.
If your still interested in pea breeding, then you might be interested in Rebsie Fairholm’s breeding projects involving peas. Not only is she breeding a very neat yellow sugar snap pea called Luna Trick, but she is also breeding an awesome red-podded pea as well! She not only shares photos and info about her crosses on her blog, but she has also provided 2 excellent tutorials for crossing peas with photos! Many of us amateur plant breeders are attempting and making progress on recreating Rebsie’s red-podded pea success here.
Trying to figure out the gentics for this rare red-podded pea is facinationg! Here are my attemopts to figure it all out with punnett squares below.
Parent Generation (P)
F1 generation if purple-pod parent is homozygous for the purple gene
F1 generation if purple-pod parent is heterozygous for the purple gene
But as it turns out, Rebsie’s results actually had mostly green pods. And upon doing some research about the genes responsible for the purple-podded trait, we actually find that there may instead be 3 genes needed for the anthocyanins to be present. One gene commonly called “A” is a master swich gene and is epistatic to the other genes coding for anthocyanins. The other two genes are also both required for the pod to have purple-pod’s. If this is correct than that means the punnit squares i completed above are no where close to being accurate. Here is the F1 hypothesis again, and this one as far as i know is correct this time. I have used the letter “A” to represent the on/off gene, along with “P” and “U” to represent the two purple-pod genes. I have left out the yellow podded gene because all offspring will be hetozygous for a base pod color of yellow/green.
Here is the corrected F1 generation hypothesis using the three genes for purple anthocyanin colors. We are ignoring the gene for green/yellow pods for the moment since all offspring in the F1 generation are heterozygous for dominant green and recessive yellow.
Here is the F2 Generation Hypothesis using the rule of independent assortment. Now this table is not entirely correct, but represents the “average” offspring collected from the purple-podded plants in the F1 generation. I say the average because in the best case scenario you can get purple-podded plants that be homozygous for ALL of the purple genes. On the other hand, the worst case scenario is that the purple-podded plants in the F1 will be heterozygous for ALL of the purple genes. In most cases though i think that the average purple-podded plant in the F1 will have two homozygous genes and the third gene will be heterozygous. In that case you would only need to worry about two sets of genes in the F2, nameley 1 set for anthocyanin and 1 set for yellow pods underneath.
Which in this “average” scenario results in the typical 9:3:3:1 Phenotypic Ratio.
And in this case the red-podded peas are the recombinant offspring that we are loking for.
If we take that a little furthur, that means that if you plant 50 F2 generation seeds, you should get a ratio of about 43 non-red pods : 7 red-pods.
Inheritance Of The Colors Of Pea Flowers
Pea flowers (the edible kind) come in three major colors. They can come in the “wild” form which is a Bicolour Purple, White, or Salmon Pink (pink-and-white). I first encountered this information on Rebsie’s blog, and after doing some research of my own, i found one refrence to the same imformation in a very old book from 1912 (Breeding and the Mendelian discovery by A.D. Darbishire). The purple form is dominant and is a trait mostly common in field peas. The pink form is recessive to the the purple, but is dominant to the white. The white form is recessive to all color, and is commonly associated with modern peas that have been selected for high sugar content. It’s a bit amusing the way the book talks about the purple form in relation to the other two. Apparently if you breed the pink with the white you will get purple in the F1 generation because the pink has the gene that expresses color, but the white is actually hiding the gene for purple flowers. In the book this is talked about as an ancestral trait, a throwback, and the theory of reversion.
In Darwins book, The Origin of Species, Darwin himself encounters something similar with his breeding of pigeons. Darwin bred a pure white pigeon with another white pigeon (with black tail feathers), and was very surprised because in the next generation he got a blue pigeon (which has the same coloring as the wild rock pigeon). But Darwin didn’t know about genetics, so he could only conclude that it was a ancestral throwback phenomenon. We now know that the white one with black stripes had the gene for color (black) and the pure white pidgeon was actually a blue pidgeon but did not have any active color genes. To my knowlwdge the only variety of pea known to have pink flowers is the one called ‘Salmon-flowered’.
Gardening this year has been sparse. Mainly Peas, Watermelon, a few purple-stalked indian corn plants, 2 sunflowers, and some pepper seedlings. However progress is being made on the pea breeding front. Thanks to Joseph Lofthouse i was able to receive a small sample of his F4 cross between an unremarkable and unnamed, but yellow snow pea and Sugar Magnolia a good purple snap pea. This has expedited my own quest for a good red podded pea.
For those who are interested roughly in how the genetics works i will give my best simple explanations here. The modified google logo above is a horrible, but extremely basic diagram of how the red podded peas are bred. It requires the combination of yellow podded peas (which are recessive) and purple podded peas which are dominant (however there are three genes involved, which means that if only some are present they are only partially dominant). Purple pods have a green pod underneath, but if you can get a yellow pod as the base color, then you get red pods. The real trick after crossing such peas is to get the recombinant offspring that you desire. You need to get two recessive genes for yellow pods in addition to at least 1 of each of the purple genes. But if you only get some of the purple genes and not two copies for each then you get splotchy pods. You get partially yellow partially red pods. Sometimes this can be fixed by just growing several generations and letting them segregate themselves. This is possible because peas are naturally self pollinating. The problem is sometimes one of the purple genes will segregate out and you will forever have only a partially red pea pod which will never stabilize unless you use it to do another cross.
Here is the predicted results of the F1 generation between a purple podded parent and a yellow podded parent, with the assumption that the purple podded parent is heterozygous for all 3 purple genes. This chart was done after reading about rebsie’s F1 generation having mostly green pods.
Here is an “average” prediction of the F2 generation. This is excluding one of the purple genes, because by this point you should be selecting from only purple pods. green pods will never give you purple pods, which in turn will never give you red pods.
Even Joseph’s F4 generation is still segregating between Snap pods and Snow pods, and red and yellow pea pods. So, I have some of my first red podded peas thanks to Joseph Lofthouse in Utah. And i’ve been doing as many pea crosses as i can myself. Not only for red-podded peas, but umbellatum types, pink pea flowers, large pods, snap pods, dwarf plants, etc. Should be fun. 🙂