Author Topic: Rice Bean Selection Projects, 2021 and on  (Read 277 times)

Jeremy Weiss

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Rice Bean Selection Projects, 2021 and on
« on: 2021-05-19, 12:00:28 PM »
Since everyone seems to be talking about their breeding and selection projects. I thought I should make a thread for my primary one (s)

Mine involve the small Asian legume known as the rice bean, Vigna umbellata (formally Phaseolus calcaratus) This is a close relative of the Azuki bean (V. angularis) and shares many similar characteristics. However being somewhat less popular (and in many places used more medicinally than nutritionally) it is somewhat less bred, and so has a slightly wider range of genotypes. 

At the moment, this is a strict selection project, as rice beans, like most of the family are nearly exclusive selfers. However at a later date, I do plan to try some intentional crosses which I will enumerate as I go.

There are three major projects

1. Adaptation and Selection of Strains that are Better Suited to Shorter Season Areas.

Among rice beans, there are two major strains. The commoner one, which has thinner, slightly smaller, darker garnet red seeds is too day length sensitive for places as far north as me (and indeed based on what others have written, possibly too DLS for anywhere but the most tropical areas of the US.). But there is a somewhat less common strain that bears larger, fatter seeds that are a lighter shade of red (sort of the color of an overboiled hotdog) which IS capable of bearing as far north as me in zone 6b (more accurately, there are MEMBERS of this population that will bear here, and can be selected for).

This part of the project I consider more or less accomplished. However due to large losses incurred from pest damage, frequent re-accessions of fresh material still need to be made often, and these always need to be vetted.

2. Preservation of Alternate Seed/Flower Colors

While a flat red color is by far the commonest color for rice beans, they do come in numerous other colors and patterns. Basically these can be divided into variations in two "layers" in  the seed coat

A. Base Color This is usually red but the exact shade of red can vary from very very light pink to deep burgundy. It is also possible to get  shades of brown ranging from a "white" (really more or a pale greenish cream) through cream, tan and brown.

A rare variant of this can also show up that produces "pinto" beans (beans with red blotches on a cream background.

B. Cover Mottling On a standard bean this layer is un marked. However it is possible to get purple/black mottling. This mottling itself varies in intensity, from a light sprinkling to very heavy. On the extreme end, the mottling can become so prevalent it covers the entire surface, resulting in a bean that visually appears black (or if the base color is "white", blue)

By and large, these alternate colors are treated as imperfections by the Chinese (the primary growers) and aggressively rogued out. There appear to be two reasons for this. The greater is cultural, and comes from the Chinese reverence for the color red (and it's implications). However it also possible that certain traits are markers for the retention of certain ancestral traits. For example, heavy mottling seems to go hand in hand with the gene for pod shattering, and very small seeds, with very small plants.

This part of the project is of moderate success. Finding alternate color beans that will grow here has been possible. However the same pest issues keep supplies low, and the ever increasing vigor at which supplies are rouged out means there is less and less alternate material available.

There is also the possibility of alternate flower colors. While yellow is the standard, I have heard that pink is possible (and the nature of genetics means that white is probably possible as well)

Should supplies ever get large enough, I plan to try and cross a mottled bean with a pinto bean, to see if it is possible to get beans that show both traits.

3. Increase of Seed Size  

As noted above the "normal" size for a rice bean is about the same as a grain of rice (with wilder ones tending to be smaller, to about half the size). However larger seeded  ones do exist, up to about the size of a navy bean (though thinner). It is hoped that this may be crossed in to improve seed size down the road

This part is not getting very far, as large seed is hard to find and, as yet none has made it to fruition.

So that is how things stand as of now. Please contact me with any further questions.