Outcrossing (dwarfed) beans

[nicollas]

Hey folks, i want to share with you an exciting project that i’m thinking about. I will not be able to work on it in the foreseeable future so i though it will be more useful to present the plan than the results as you clever and skilled gardeners could start doing stuff with that.

Start of the project is a bean mutant that is dwarf and with a much more outcrossing rate than usual beans. It comes from a single recessive gene termed do (=dwarf outcrossing).

In the studies, the natural rate of cross pollination was 10 - 56% The higher cross pollination is due to a “delayed anther dehiscence”, so that means the flowers opens but pollen has not yet been released on the stigma, whichs leads to opportunity of a pollinator to first pollinate the flower. So this not the same mechanism as P. coccineus or any sterility so the pod set should be very good anyway (the stigma will be covered by the flower’s pollen anyway)
The hand pollination of do/do plants without emasculation in the morning gives very good percentage of cross pollinations too.

So now the bad part, the dwarfing. I dont remember if the gene control the two traits or if it is just strongly linked. Dwarfness is due the shorter internodes, smaller leaves, and maybe slower growth. I remember reading that combination of do/do plants with the bush type gives plants that can’t compete with normal bush types, so maybe this trait is only useful keeping in vining or semi vining types.
The good side is that it acts as a precicious marker for plants homozygous for the do variation.

So from here i can see two options :

Landracing beans, the Lofthouse way, keeping a lot of dynamic genetic pool of do/do individuals. Maybe the best solution is to keep a patch specifficaly for introduction of regular plants to intercross wih a part of the landrace to then segregates for do/do plants to bring back to the landrace ? Managing do/do and +/do plants together could be tricky as +/do may outcompete the others ?
Using do/do plants as proxy to mix a lot of genetic from regular plants and then selecting only +/+ to breed new cultivars easily (either by passive pollination, or by hand pollination - very high percent of takes without emasculation making it possible). What is cool with this project is that one can select do/do plants closer to good agronomic cultivars at each stage so you end up mixing directly two good genomes and select from thant. One can even imagine creating near isogenic lines of some favorite cultivars (variating only at the do locust) to makea lot of hydrids with this cultivar.

So where to obtain the germplasm ? Here it is : npgsweb.ars-grin.gov/gringlobal/accessiondetail.aspx?id=1478595
Please check that the plant looks like dwarfed, because by def this could have been crossed and selected for the wild type


I uploaded the docs here : drive.google.com/drive/folders/1A8gNYc8hiMMR12X1K7NHlAHUgvmMTKru?usp=sharing
I dumped one of the doc into multiple images because i had issues viewing it.

[nicollas]

Image from the GRIN page : left is regular type. One can see the shorter internode

[walt]

Thanks for the heads up on this.  It could be very useful in the early years of starting a landrace.
Much work with barley shows that after a few generations, a high crossing rate is much less important, each seedling is still pretty heterozygous.  But getting started, that is where the work is.
The barley work was done by starting with various crosses, then leaving the population alone.  They didn't bring in new varieties at a later time.  A gene like this could ease feeding new varieties to an established population, as well as starting a new population.
I might use this in crossing common beans with runner beans.  Not that I need more work.

[reed]

Had to read this a couple of times, first I was thinking why in the world would anyone want dwarf beans. After rereading, if I understand correctly, it's the ease of crossing rather than the dwarfish growth that's attractive. Then I got to thinking the dwarfish growth  itself  might also be an advantage in some applications.

The short internodes or dwarf habit on a pole variety might be nice. Maybe it could be used to reduce the height of larger pole types. Say 15' down to 7 or 8. That would be useful. Also might it cause lots of beans to be produced close together on the vine? That might also be useful.

I'll be keeping an eye on this thread.

[walt]

My seed arrived yesterday.  Very small beans.  I'm eager to get them in the ground and get them crossing with Pinto, Great Northern, Red Kidney, and Black Turtle.  May start a green bean intercrossing population, too.  Why not?  

[Srdjan Gavrilovic]

May 26, 2018 11:11:02 GMT -5 walt said:

My seed arrived yesterday.   

Where did you get your seeds from? Can I enlist myself for few excess DO seeds that you might have by end of the season?


This is very similar approach to my tomato breading attempt.
I got Micro Tom to use as mother plant. Very tiny plant, flowers at stage 3-5 leaves and phenotype can be scored at stage of first true leaf (in my limited experience even at cotyledon stage). When starting indoors this is huge help.
Plants are small enough to be easily grown in pots and moved around garden closer to plant you want to cross it with (either intentional crossing or to let insects do the work).

www.dropbox.com/s/71w6ofuf1fzfa2h/2018-06-01%2020.49.25.jpg?dl=0

It is picture of Micro Tom (in flower) in front and out-crossed half-sibling (it comes from original package and 2nd parent is unknown). My seeds have ~20% of similar hybrids. Normally, it is recommended to weed them out, as soon as possible, due to not being pure but for me these F1s are way to important to waste them

By end of season I'll have enough of Micro Tom seeds to share. I absolutely cant guaranty purity but it will be easy for everyone to select in either direction within few weeks post germination.

Best, Srdjan

[walt]

Srdjan

npgsweb.ars-grin.gov/gringlobal/accessiondetail.aspx?id=1478595

Click on the address above and you can get it sent to you.   Or, send me your address and I can send some of mine.  They sent me more than I need.
Walt

[walt]

Srdjan.  How did your Outcrossing (dwarfed) beans do?  I planted 3 of those beans.  They grew OK. though dwarfed, as expected.  But they never bloomed even once.
I have about 10 seeds left, so I'll try again next year.  But so far I am not impressed.

[Srdjan Gavrilovic]

Nov 8, 2018 15:19:56 GMT -5 walt said:

Srdjan.  How did your Outcrossing (dwarfed) beans do?  I planted 3 of those beans.  They grew OK. though dwarfed, as expected.  But they never bloomed even once.
I have about 10 seeds left, so I'll try again next year.  But so far I am not impressed.

I got them late for my season and did not plant them at all. Keeping for next year.

The way I understand, these beans are not likely to perform well anywhere. They were identified following saturation mutation. In other words, original population was exposed to huge amount of mutagen, left to grow and screened for interesting phenotypes in following generations. The thing is that each line has large number of background mutations of which at least some have penalties (in addition to the mutation of our interest).
For that reason, I plant to out-cross them with multiple other lines and try to remove some of those other unwanted mutations (plus introduce few properties for further breeding). F1 plants should be easy to identify by "normal" growth and I'll use seeds from those plants for sowing and selecting for dwarfs (~25% of seedlings).

I have your seeds and can send you back. Also, I would be happy to send you any of segregating lines/seeds from successful hybridization.

Best, Srdjan

[nicollas]

They grew and podded without diifficulty the year i've grown them

[walt]

Srdjan
I also planned to cross them with well adapted varieties, and from those crosses develop a well adapted open pollinated population.
I still have enough seed to try again next year. Thanks for the offer. If I don't get some crosses next year, I might take your offer of F1 or F2 seeds.
But I might not. My citrus breeding is taking more of my time than anything I've tried on my own. And it is a lot of fun. I'll have to see how much time and space I have for other projects.
Walt

[imgrimmer]

I have 1 seed germinating right now. How are yours?
I wonder how I can find outcrossing plants later in the f4 f5 and so on. I can judge by the offspring but i would like to cull all none outcrossing plants already in season.

[walt]

As I understand it, the outcrossing  gene and the dwarf gene is the same gene.  All non-dwarf plants from seeds of the dwarf plants are hybrids.  In the F2, all dwarf plants will be the more outcrossing type flowers.  The outcrossing dwarfs will have some selfing.  They do make pollen, but the pollen matures late, increasing the outcrossing rate.
So the only difficulty, using this gene, is getting the dwarfs to grow.  So far, they seem to have very low vigor.  But this shouldn't affect the hybrids or later generations that don't carry the gene.

[Srdjan Gavrilovic]

Correct, it is the same gene causing pleiotropic effect (dwarf plant and late maturing pollen). Selection strategy will be different depending what you select for (and cross with). In my case, I plan to cross with greasy beans and select normal growing plants in F1 (dwarfs will probably kept for seed production). In F2 I'll look for dwarf AND greasy pod phenotype combined in a single plant (or at least as close as one appears).
Due to a plethora of other mutations that this line has, other things can be selected for or against. F2/F3 might need to be crossed/beck-crossed in order to stack other properties I look for with dwarf phenotype.
For downstream generations, I'll look for the best plant I can find for crossing into perennial beans lines (separate lines, selected only for survival under local conditions without any care given to yield components).

This is not a short path and unless you know where you want to go, it is easy to get lost