Author Topic: Directing Crossing by Bumblebees  (Read 369 times)

reed

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Directing Crossing by Bumblebees
« on: 2018-12-30, 08:52:32 AM »
For past several years I'v made a point to closely observe the pollinators in my garden and Bumblebees stand out as one, if not the most important. Their behavior is interesting. I'v noticed they are very methodical in their methods. They move from one flower to the nearest adjacent rather than flying around at random like some things do. Makes sense, not to waste time and energy. I also notice they some how know when a flower has already been visited by themselves or another bumblebee, they may give it a close fly by but they don't land on the same one again. I wonder if they leave some chemical tag that the flower is used already.  If there is some other critter on a flower they may aggressively bump into it and scare it off or they may just go to the next flower.

I have a theory that I can use their behavior to make controlled crosses.  For example I think by planting a single plant of a bean I want crossed among many plants of the selected father I can greatly increase the % of crossed seeds on the mother plant. I also theorize that by watching closely, arranging the blooms to be within an inch of each other and removing all but one bloom per stem of the mother I can increase it even more. Of course there will still be self pollination going on as well but I bet growing a pod or two worth of seeds would show some to be crossed. 

Same process would work for many other things, limit # of flowers on a mother plant, arrange those you leave to immediately beside those of the father plants. Not as exact but much less tedious than actually dissecting a flower and hand pollinating. If my theory is correct then all else that's needed is to grow the seeds and find the crosses.

Joseph Lofthouse

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Re: Directing Crossing by Bumblebees
« Reply #1 on: 2018-12-30, 09:42:47 AM »

When a bumblebee harvests pollen from a tomato flower, it leaves dark bruising behind on the anther cone. I also wonder if their vision is acute enough to see pollen grains coating a flower?




Mike Jennings

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Re: Directing Crossing by Bumblebees
« Reply #2 on: 2018-12-30, 10:53:58 AM »
Iíve definitely read about some species of legumes, where the flowers change color or close up after they have been visited by a bee. Sometimes they will also change back if they have not been sufficiently pollinated. Iím not sure if it happens in leguminous crops, though. Might only apply to outbreeding species.

https://www.nationalgeographic.com/science/phenomena/2009/06/15/flowers-change-colour-and-back-again-to-advertise-their-opening-hours/

bill

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Re: Directing Crossing by Bumblebees
« Reply #3 on: 2018-12-30, 01:27:58 PM »
I grow in phenotype blocks to maximize the kinds of pollination that I want.  This is particularly true with potatoes.  Each block is separated from another by about a 10 yard gap with taller plants of a different species in between.  This keeps many pollinators from going too far afield.  When I want to get a reasonable portion of a particular cross but I can't be bothered to hand pollinate, I alternate varieties in a row.

This all works well as long as you are willing to tolerate a lot of self-pollination and a little bit of outcrossing.  I am more bothered by the selfing than outcrossing.

Joseph Lofthouse

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Re: Directing Crossing by Bumblebees
« Reply #4 on: 2018-12-30, 02:09:42 PM »
I grow in phenotype blocks to maximize the kinds of pollination that I want. 

I do something similar with squash...  The pinks on one end of the row, the greens on the other... Then pinks tend to be pollinated more often by pinks. I might also separate patches of squash by 100 feet, so that each patch is about 95% crossing within itself, and about 5% crossing between patches.

Or I'll put necked squash on one end of the row, and pumpkins on the other... etc...

reed

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Re: Directing Crossing by Bumblebees
« Reply #5 on: 2018-12-31, 04:28:12 AM »
Yea, the concept is pretty simple with things ordinarily pollinated by bees. I'm gonna use it to try to start identifying compatibility of particular sweet potato lines this coming year but I'm looking mostly at those things usually self pollinated like beans and tomatoes. There will be high numbers of selfed seeds to filter out later but I think especially for beans, limiting the # of flowers on the mother plant and making sure they are in very close proximity to the father plant's flowers will greatly increase the % of crossed seeds.

Say for example there are 50 bean flowers in a 2 sq ft area. 49 are the father and 1 is the mother. Chances a bee has visited one or more of the 49 before it visits the 1 are pretty good.  Chances of a successful cross and a maturing seed pod is probably better than if I go at with tweezers. 

Mike Jennings

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Re: Directing Crossing by Bumblebees
« Reply #6 on: 2018-12-31, 01:49:04 PM »
I do something similar with squash...  The pinks on one end of the row, the greens on the other... Then pinks tend to be pollinated more often by pinks. I might also separate patches of squash by 100 feet, so that each patch is about 95% crossing within itself, and about 5% crossing between patches.

Or I'll put necked squash on one end of the row, and pumpkins on the other... etc...

Joseph, what is the purpose of (semi) isolating the different squash phenotypes? I would have assumed that you might sow everything mixed to maximize heterogeneity in each plant of the following generation.

Do you do this to maintain recessive traits, that might otherwise be hidden, if your population consists of mostly new "wide crosses" each year?

Mike Jennings

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Re: Directing Crossing by Bumblebees
« Reply #7 on: 2018-12-31, 02:07:53 PM »

Say for example there are 50 bean flowers in a 2 sq ft area. 49 are the father and 1 is the mother. Chances a bee has visited one or more of the 49 before it visits the 1 are pretty good.  Chances of a successful cross and a maturing seed pod is probably better than if I go at with tweezers.

Good idea, Reed. I may have to try that too.

I have done something similar when crossing outbreeding crops, like brassicas, where I leave only one plant of the mother variety to flower near many plants of the intended father. This gives pretty good results.

When using your idea for something like beans, it might be good to keep selecting a new flower to leave on the mother plant after the previous one begins to form a pod. If you ended up with only one pod and like 8 potentially crossed beans, that might be low odds of getting one that was not selfed. ...but you probably thought of that already. :)
« Last Edit: 2018-12-31, 09:25:38 PM by Mike Jennings »

Joseph Lofthouse

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Re: Directing Crossing by Bumblebees
« Reply #8 on: 2018-12-31, 02:31:47 PM »
Joseph, what is the purpose of (semi) isolating the different squash phenotypes? I would have assumed that you might sow everything mixed to maximize heterogeneity in each plant of the following generation.

Do you do this to maintain recessive traits, that might otherwise be hidden, if your population consists of mostly new "wide crosses" each year?

Yes. Exactly! To maintain recessive traits. For example, if I intermix the moschata pumpkins, and the long-necked butternuts, then I end up with a lot of football shaped squash among the offspring. But if I plant the rounds on one end of a long row, and the long-necked on the other end, then the offspring are mostly rounds, or mostly long-necked, with a few intermediate types.

It's more complicated with the maxima squash, cause there is green or orange skin, and then a modifier for intense or pale coloration. So that ends up producing dark green, orange, "gray", and pink fruits. I don't have a good semi-isolation strategy for these. I might move towards growing 4 semi-isolated patches, one for each color. Perhaps separated by 30 feet.

I used to grow the different colors of sweet corn in small patches separated by 11 feet. That allowed me to have cobs that were mostly white, mostly yellow, mostly red, mostly gray, etc, while still allowing crossing between them.

In the early generations of a landrace development project, I closely inter-plant  the different varieties. Later on, I tend to semi-isolate types that are most pleasing to me.

Carol Deppe

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Re: Directing Crossing by Bumblebees
« Reply #9 on: 2018-12-31, 08:31:06 PM »
Around here, in Willamette Valley Oregon, bumble bees and honey bees visit squash flowers multiple times. With cool moist spring weather, the anthers tend to dehisce (release pollen) one anther at a time instead of all at once. so full pollen release occurs gradually over a period of about an hour. And each flower gets visited over and over as the pollen release progresses.

Bees here seem to visit nearby flowers of the same species preferentially to ones farther away or even nearby but of different species. And if they are working on beans, for example, they will mostly go to the next plant in the row, or down the row more often than skipping to the next row.

Under organic growing conditions here, I get about 5% crosses if I interplant two different varieties of my dry beans. And I normally make crosses just by interplanting. However, I interplanted a bunch of bush green bean varieties in pair-wise combinations a couple years ago and grew them out last season, and had no crosses. Grumble, growl. Likewise with cowpea project. Looks like I will need to hand pollinate to get those crosses.

reed

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Re: Directing Crossing by Bumblebees
« Reply #10 on: 2019-01-01, 05:48:37 AM »
I haven't paid much attention to the bees behavior on squash, only to notice there will often be more than one at a time on a flower. Sometimes they seem to hang around and have a little meeting. Honeybees like the early fruit tree flowers but I very rarely see a honeybee in the garden except occasionally on corn tassels.

My closest observation of bumblebees has been on sweet potatoes. Those flowers open in the morning, some earlier than others and on a clear sunny day start to fade in just a couple hours. On a cloudy day they may last into the afternoon. The bees come early, visit all the fresh flowers and move on to something else.

I don't have a guess on % of crossing in my beans but it's way more than I used to think. Now that I'v  greatly increased growing for dry beans rather than canning them all like we used to, I find them all the time. I don't think it's just in my garden. I do grow outs for a fellow in Illinois that has a giant bean collection and I find off-types in half or more of the samples he sends me.

Joseph Lofthouse

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Re: Directing Crossing by Bumblebees
« Reply #11 on: 2019-01-01, 07:11:42 PM »
On my farm, the primary pollinators of cucurbits are "Squash Bees", the Eucerini tribe. They are very active first thing in the morning, and pretty much harvest the available pollen before honeybees or bumblebees are active.

Squash Bees