Hand-pollination to increase genetic diversity

Most of the time people hand-pollinate in order to do one of two things:

  • Ensure that there’s no crossing in order to maintain an inbred variety.
  • Ensure that there IS crossing in order to get a hybrid.

The latter is obviously a way to increase genetic diversity, which is great. But it still requires forethought and planning and covering the female flower in order to make sure there is no pollen from any other plant than The Chosen One, and that’s a pain.

What if there’s another way?

What if, whenever you see an open female flower on one of your favorite plants, you pick a male flower from every other plant you like and then go pollinate the same female flower with them? Seeds in the same fruit can have different fathers, so I think you’d end up with a ton of genetic diversity in the offspring.

I’ll go a step further. Since you probably don’t want to save seeds from only one fruit (it’s a good idea to have different mothers as well as different fathers, so that you preserve diversity of cytoplasm), why not do that as a habit whenever you have a few minutes and you notice a female flower open on a plant you like?

I can’t see any reason why that would cause problems. You wouldn’t even have to mark the hand-pollinated fruits unless you felt like it. You could just do as many as you happen to notice, and then save seeds from your favorite fruits at the end of the season. Some of them are bound to be ones you hand-pollinated.

It seems to me that may be an easy, lackadaisical way to get some extra crossing, and maybe speed up local adapting.

2 Likes

J Larsen
you could also take the male flowers from plants you’ve already marked, for things like robust growing, or first to sprout, etc. I like this idea I wonder if anyone has already tried it

Jesse I
Not sure how it’s with all the plants, but atleast some have same “winner takes it all” principle as humans. Even those that can have multiple, I would guess it’s still first come first served. So there might not be as much mixing as you would think, but maybe someone knows plant reproduction more intimately to elaborate on that. How you cross them depends much on the plant and their flowers. Cucurbits I have just taken female flower from one plant and pollinated other plant to increase outcrossing in general, but also give stronger plants better change. Didn’t use bagging unless really wanted some cross. In tomatoes or peppers this might not be as effective as flowers have their own pollen. Also they dont outcross as easily naturally so I want to make sure they cross as i dont have as much space to look for crosses. I dont bag them as removing pedals makes then quite unattractive to pollinators anyway. Might make manual crosses several generations to make sure there is good mixing before letting nature run it’s course mostly. Manually crossing those that do not outcross as easily does have the advantage that you know it’s a cross. Those that outcross more freely it’s easier to just let go of the control, but still I would make sure I get those first crosses to atleast give different varieties change to contribute.

Emily S
See, I got the idea because I found out that sperm doesn’t actually work on a “first-come, first-served” basis with humans. The egg will actually choose between a dozen or so of the early sperm that arrive, picking whatever seems most suitable. My suspicion is that gametes in other species likely work the same way. (It’s easy to find litters of multiple-birth mammals, like dogs and cats, where all the babies had a different father, for example.) If my hypothesis is correct, that means if you put pollen from ten plants onto that female flower within a few-minute period, I don’t think the first male flower to contribute pollen will have a significant advantage over the rest. Instead, whatever is the most suitable will probably get chosen. Since that specific plant is likely be more qualified to know which among those options is the best for its offspring, you might get the strongest possible offspring that way.

Ryder T
Just found this: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3576585/

Joseph L
that article makes it seem like the best answer is to take a q-tip and just use the same q-tip for all the blossoms that are out of a given plant like you’re a bee, then a new q-tip for the next plant type.

Jesse I
Ok, did not think that way, but still it wouldn’t lead to multiple fathers I think; either it says yes to all or no to all of one kind. Maybe if the timing is just right, but only for those species that can be pollinated by multible pollen. I did try similar idea with peppers once, but was told that only one pollen does the pollination on peppers (thus comparison to humans). So nature is wastefull. Many flowers have limited timespan soI would think they would take any suitable pollen, but your right they might reject some. I think that would be self-incompatibility though.

Emily S
Interesting! So that probably wouldn’t work well on peppers. I wonder if that’s true of all nightshades. Has anyone ever seen multiple fathers in seeds from the same tomato, potato berry, eggplant, tomatillo, ground cherry, or another nightshade? My (admittedly limited) experience with pepo squashes indicates that this would work well for them. The seeds I saved from the same spaghetti squash fruit included a) obvious purebreed spaghetti squashes, b) obvious spaghetti zucchini crosses, and c) obvious spaghetti pattypan crosses. My suspicion is that if it works well on pepo squashes, it will probably work well on most cucurbits.

Julia D
Yes… Darwins’ book describes how they first pollinated a plant with a sibling, then a few days later pollinated with a non related plant. Plant rejected the first one in favor of diversity… There’s a lot out there on quantity and diversity of pollen increasing everything. Bill Whitson (cultivarable) described something like collecting pollen from a bunch of different donors, aggregating it, then going around dusting it on other receptive potato flowers. I think you should do this for sure, and make a whole video about exactly how you do it and why :slight_smile: Just make it easy enough for me please!

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Jesse I
Wouldn’t that be self-incompatibility? It does makes sence to overcome that (and other incompatibility issues), but would depend on plant species if it’s possible to have multiple pollinator or if it’s just one that pollinates in anycase. There might be also issue that some plant makes less pollen than other and thus has disadvantege in pollination in mix with others. So if there is plant that you really want to have in a cross I would have that as the plant being pollinated or do cross with only using it’s pollen. Otherwise mixing might be effective, but I like faster way of just taking one flower, using it some time, then taking other from different plant and use it for the next flowers.

Emily S
That’s very neat! And very hopeful. That’s a very good point, Jesse. Julia, do you know if Darwin tested the same plants to see if the flowers were self-incompatible?

Yeah, I agree that if you really want a specific cross, you should bag the female flower. This approach would work best if what you want is to try to speed up the quantity of any crossing.

Not self incompatibility, he was talking about (far as I can tell) a plants ability to choose if given more than one option (and self pollination or close relative is a last resort). Many of the plants he described could be self pollinated if not given an option. I found one of the passages, from my memory there was another but I haven’t found it yet.


That still sound very close to self-incompatibility and self pollination as a back up. Many generally self-incompatible wild tomatoes and physalis seem to have self-compatible populations which is propably how modern came to be self-compatible (with possible self-incomtible traits). But I think Emily was referring to different idea, that both would pollinate which very much depends in what kind of flower plant has.

For plants whose flowers have both male and female parts, I guess that would mean destroying half of all the flowers in the process. Also if you showered the female with flower/part with pollen from one flower than that might do all the fertilising and the later flowers picked for pollen might be wasted.

So, how about first gathering pollen producing flowers from all the plants you want to, then collect their pollen in one container all together, all mixed up. You can store pollen in the fridge at least for days but I think more like weeks or maybe even months, depending on the species I guess, and the temperature and maybe humidity? So if you used this randomised mix to squirt at all the female flowers, that might give you a better chance of more diverse results?

And I guess for self fertile flowers, the manual method of emasculating flowers can be pretty important, right? I hope to be trying this for soy beans and rice, since I don’t think they would naturally cross much at all. I would seem to me that doing a year or two of manual crosses, or maybe even growing inside over winter so you can do two sets of crosses per year, would be a useful way to establish a hybrid swarm very quickly that might take nature a few decades or more to do.

Collecting all the pollen, mixing it up, and then spreading it with a Q-tip sounds like a great idea! Particularly for those little tiny flowers on crops like beans.

I’m wondering if you wouldn’t have to emasculate the flower in order to do this. Wouldn’t the plant’s ovules prefer different pollen than its own? In theory, it seems likely they would. Especially since, even with inbreeders that rarely get pollinated, crossing can happen. That seems to imply to me that inbreeding crops don’t have to be emasculated in order to grab diverse pollen whenever it’s offered.

It would be interesting to see if that’s true. It would certainly be less bother. I suppose the best way to find out would be to try it.

Sounds like it’s possible, but might differ greatly with different species. Also I do wonder if Darwins experiments translate to today. After all agriculture has changed greatly and those traits might have been lost or become more rare. Genes that are not used usually go dormant or are lost completely. Atleast my experience in peppers says that it doesn’t happen on them. So many years I have grown dozens of plants in close proximity and they seem to come true to variety almost always. Possibly needs to get the active gene from somewhere. Beans I haven’t got experience that much, but I thought next year i might do crosses and than just let nature do slow work. Not as conserned in getting fast results on them as in some other species.

If you’re happy with the beans you have now, it makes sense to not be concerned about getting fast results with them.

I’ve had fairly poor results with common beans so far, and I really like beans, so they’re going to be one of my main priorities next year. Tepary beans did great, so I may grow them instead of common beans, but I’d rather grow them “as well as” instead of “instead of.”

I’m planning to try cowpeas, runner beans, and fava beans next year, as well. I ought to be able to get something to survive!

After survival, taste, and productivity (obviously priorities if I want them to give me food I can eat), I’d really like to have beans in many different colors with different patterns on them. Beans of all colors of the rainbow clustered together are so pretty!

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So far just experimented with dry beans and they aren’t definetely as far as they should, dont have enough time to have them fully dry on the plants, but I can easily get seed which takes of the pressure of getting some fast results. I’m getting some of Josephs dry beans for next season so there will be some divergence between generations in any case. Many other species I still have lots of crossing to do so atleast for now I dont use that much time on beans.

Cool! And Joseph has a short season too, so maybe his beans are already well adjusted to a short growing season. That would be helpful!

The ecosystem does the breeding. I just try to stay out of the way, and encourage them to cross-pollinate, as much as they can.

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That’s one of the things I love about landracing. It’s the lazy way to garden, and it also works better than most labor-intensive methods! Truly, micromanagement is usually counterproductive. It’s better to choose your partners well, and then trust them to make good decisions in their stewardships.

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When doing wide/speculative controlled crosses I think the idea of pooled pollen from multiple species is a great strategy. It means you are much less likely to get zero seeds from each hand pollinated cross. Nothing worse than spending weeks doing controlled hand crosses and getting nothing at all from your efforts.

If you keep track of the female/seed parent identity of anything that sets, plus a list of all the potential pollen donors used, it means you can usually identify the likely pollen parent from any hybrids produced. That saves on an enormous amount of labelling.

Then next season you can remove any successful pollen donors from the pool if you don’t need any more of those crosses, in order to give the other pollen donor species more of a chance.

That makes sense! I could just, say, make a list in my garden spreadsheet about everything I tried pollinating a flower with. That’s the easiest way to keep all the data without having to have tags in my garden.