Green cotyledon fava bean

[Klaus Brugger]

I've stumbled upon this tweet by Dr. Hamid Khazaei showing a mature Vicia faba seed with green cotyledons, sourced in the Middle East. There's at least one other green cotyledon source, a spontaneous mutant found in the 90s in China (Duc et al., 2008).

Has anyone here come across such a phenotype already?

Duc, G., Moussy, F., Zong, X. and Ding, G. (1999), Single gene mutation for green cotyledons as a marker for the embryonic genotype in faba bean, Vicia faba. Plant Breeding, 118: 577-578. https://doi.org/10.1046/j.1439-0523.1999.00422.x

[Jeremy Weiss]

Not sure. I've come across green cotted peas, soybeans, chickpeas, lentils, Siberian pea shrub seeds, and cowpeas, but as my sources of favas are fairly limited, I can't recall if I've ever seen any with green cots.

However, since so many legumes DO have them, and since it is basically only one recessive gene that does it, it would hardy SURPRISE me if they existed.

And I've certainly seen green cotyledons in OTHER vetches, like V. sativa. However changed Favas may be from their ancestors, they are still vetches, and presumably still have all of the genetic options available to vetches.   

[Tim DH]

I'd not ever thought of this as a thing!

I'd assumed that my green seeded beans has green cotyledons.

Hopefully I'll remember to check next spring!

Tim DH

[Jeremy Weiss]

Nah, most of those are yellow inside, same as with green skinned peas.

Though greenness can be ambiguous. I actually had to grow some green chickpeas through a year to confirm they were actually green since a lot of "green chickpeas" sold on the Indian grocery cycle are regular chickpeas that have been picked young and dried in the shade. But I let them go full term, and they stayed green, so I guess that confirms it.

And the green inside cowpeas is not only sort of rare (I only seem to find it in one kind, a black skinned kind that hails from somewhere in the Thailand-Vietnam area) but a bit hard to see (since "normal" cowpea insides are light buff, and not yellow the green is similarly pale, and tends to fade in exposure to light and air.) Again, I had to grow some full cycle (or rather, have someone else do it for me) to confirm they stayed that way.

[Joseph Lofthouse]

I cracked a bunch of fava beans from my landrace. Most of them had pale yellow cotyledons. I found one with a green cotyledon.

[UnicornEmily]

I cracked a bunch of fava beans from my landrace. Most of them had pale yellow cotyledons. I found one with a green cotyledon.

That's neat!  Can it still be planted after breaking the husk that way?  If so, that may be an interesting way to check for color of cotyledons before planting.

[Jeremy Weiss]

That's neat!  Can it still be planted after breaking the husk that way?  If so, that may be an interesting way to check for color of cotyledons before planting.

If he managed to get the seed coat off without damaging the insides, yes, one can (though they will be slightly more vulnerable to diseases than with an intact seed coat, so one might have to keep a closer eye on them). Whenever I am trying to do either the soybeans or cowpeas I find, I HAVE to remove a bit of seedcoat off of each one, as both have black seedcoats (so I have no clue what color the insides are just looking at the seed) and come with both green and yellow insides mixed (in the case of the soybeans, I think it is less of a case of the Chinese choosing green cotyledons as much as them deciding that, for the black skinned soybeans (which are used for things like black bean sauce and soy sauce) it doesn't MATTER what color the insides are, since the end product will be black/brown anyway. Whereas with tofu or soy-milk, the beans HAVE to be yellow inside, or the milk or tofu will itself be green (it's not an unattractive green (sort of the color of melted green tea ice cream), and tastes just the same (I've made some), but people have their food prejudices.

That's actually the major limiting factor in my growing of either of those. I can get both in basically unlimited quantities, but there are only so many beans I can scrape a bit of seed coat off of one by one before my wrists go out from repetitive stress injuries. And there's no mass mechanical method I can think of that wouldn't also break the two cotyledons apart and kill the seeds in the process. 

[Joseph Lofthouse]

If I were selecting for green cotyledons, I'd likely do it by pre-soaking the beans, and sorting them just after the seed coat splits, then planting the green seeded together in a patch.

The off-type rate of fava seedlings in my garden is around 30%, but I could move a population strongly in the direction of green cotyledons.

[Jeremy Weiss]

If I were selecting for green cotyledons, I'd likely do it by pre-soaking the beans, and sorting them just after the seed coat splits, then planting the green seeded together in a patch.

The off-type rate of fava seedlings in my garden is around 30%, but I could move a population strongly in the direction of green cotyledons.

That would be a good idea, except that soaked beans SMELL stronger to animals, and that makes it even easier for them to  find them and dig them up. Plus, if the beans have black skins (like these do_ the skins stain both the water and the cotyledons, so what was yellow vs. green dry becomes more of pinky brown vs. slightly greener pinky brown.

The ratio in the stuff I have found varies. The cow peas are about 25-30% as well (which would make sense, from a Punnet Square POV). Soy tended to vary from distributor to distributor, some are mostly yellow, some are about 50-50 and some have green as the majority. Smaller seeded types tend to show the colors (both green AND yellow) more strongly. 

[Klaus Brugger]

Thank you for all your interesting answers!
A clear seed coat like in many peas would make selection for cotyledon colour much easier of course, but I'm not sure if such a trait is present in fava beans (and you don't necessarily want a clear seed coat, of course) ...

[Jeremy Weiss]

As far as I know, it does not. With favas, I think light tan is about the palest you can get.

Bear in mind though, that I thought the same thing was true for horse gram (Dolichos biflorus) until I actually ENCOUNTERED white ones.