Tepary bean population breeding, differentiating them.

[Ocimum]

Hi,
I am interested in a tepary (Phaseolus acutifolius) population. I got some "black mitla" among others, but they look more like Phaseolus vulgaris.

Does anyone know if there is a way to differentiate between the species based on seeds only? Or does anyone know other differentiating traits other than the leaf angle?

[Jeremy Weiss]

I won't pretend to be all that knowledgeable about teparies, but, based on the ones I've seen, the seeds tend to be quite a bit smaller than most vulgaris, often look sort of withered or wrinkly (as if they weren't quite full when they dried) and, compared to a vulgaris bean, the hilum tends to be a lot smaller.

[Ocimum]

Thanks Jeremy, I have also noticed the wrinkled seeds and wondered if it was due to incomplete development of the seed, or something similar to sweet corn, that starch was not developped

[Jeremy Weiss]

I think it's just a function of the thinness of the seed coat, the same way that the white part of many cowpea seed coats (like on a black eyed pea) are often thinner and more wrinkly than the seed coats of other colors.)

It also occurs to me that, if you evolve in an arid climate where water is scarce, having wrinkles and folds in your seed coat is a good way to make sure that water than touches you stays stuck to you longer, increasing time to absorb and imbibe it. Same reason a lot of desert plants have leaves covered with fine hairs, the hairs catch a lot of the water that is lost during transpiration (and coagulates at night due to condensation) and drips it back on the base of the plant (it also helps with UV protection.)

[UnicornEmily]

I've been told that Black Mitla is a common bean variety that was mislabeled at some point as a tepary.  I grew a bunch of Black Mitla plants this year, and I can confirm that their leaves and behaviors (and lack of drought and heat tolerance) are totally common bean, not at all tepary bean.