Bees - cross pollination of tomatoes

[TZ -OH6]

Cross pollination has come up in a couple of threads so I thought I would dig out some pictures.

http://www.flickr.com/photos/51251503@N ... 324605541/

Note the size of the bees (smaller than a house fly). They only stay at a flower for a couple of seconds at most so unless there are a lot of them working the plants they are very hard to notice.

A tomato self pollinates in a couple of ways. At the late bud stage the stigma starts to elongate and can (rarely) pick up pollen on its way out of the anther cone. Later, after the blossom opens pollen shakes loose creating a mini dust cloud around the stigma. Anything that can jostle the blossom will create more of these little puffs of pollen. As far as making seeds goes the first pollen grains on the stigma usually gets to the ovules first when everything is working as it should, but mostif not all of the pollen matures after the blossom opens, high temps kill pollen, high humidity clumps it together so it won't fall out, calm days do not promote pollen release, etc.


http://www.flickr.com/photos/51251503@N ... 324605541/

The pollen matures over a period of time and is released only at certain times (mid morning to mid afternoon). Bees scent mark flowers with each visit so that they don't waste time with a flower that has just been stripped of pollen. That is why they seem to look at alot of flowers and not land or simply fly on by. This is also why they may skip over several plants and hit flowers quite far apart from each other, especially on days where the are a lot of bees around.


http://www.flickr.com/photos/51251503@N ... 324605541/

All showy flowers have evolved to be pollinated most efficiently in a certain way, usually through a specific action of an insect. Tomato flowers and some others are built to be "buzz pollinated", whereby a bee will vibrate the flower to shake pollen loose. These flowers usually have a funnel shaped anther cone (anthers fused or hooked together) with pollen released on the inside surface of the cone to shake past the stigma (tomatoes), or to be released through pores at the tip of the anthers (potatoes). Bees in tomato greenhouses are significantly (economically) more successful in setting fruit than any other method.

Honey bees, unlike most bee species, collect nectar to stockpile honey as a winter food source for the hive. While they are doing this they are also collecting protein rich pollen to feed their larvae, so they tend to ignore small flowers that don't have nectar. Most other bees just need the pollen for their young, and maybe a little nectar for their own food. They lay and egg in a chamber, stuff in as much pollen as is needed for complete development of the larvea once it hatches, and then seal off the chamber only to start the process over again. The more pollen they can collect the more eggs they can lay so they will work themselves to death, flying several hundred yards from nest to flowers round trip.

Will planting a few of any one variety close together cut down on cross pollination? I doubt it because the scent marking causes bees to skip over so many flowers. You would need distinct separate patches with a good number of plants for each bee to coat itself with pollen from only that patch. Number of plants (total number of flowers) would be more important than distance.


Cross pollination statistics:. In a mixed tomato garden cross pollination per fruit will range from 0% to (rarely) around 40%.

http://www.southernexposure.com/isolati ... oes.p.html

This often cited article gives a value of 2%-5%, but also mentions other studies with higher values. Because of the many factors involved (number of bees, weather conditions, etc) the value can shift wildy over the course of a season in any one garden (I get around 0%-5% for first fruits, and 20% mid season).


What is the easiest way to prevent cross polination? Bagging blossoms (actually bagging buds so that the blossoms open in the bag). Places like Walmart and crafts stores sell organza drawstring sachets for something (my masculinity might be threatened if I knew what people normally do with them). Just slip the bag over a truss of unopened buds and wait for small fruit to appear in the bag, remove the bag and tie a bright marker on the truss, and make if very clear to anyone in the area not to pick those fruit. I find it easier to cinch the bags down if I turn them inside out first, that way the cuff doesn't get in the way.

I suppose you could take a piece of tulle netting and some string and tie a make shift covering over a bud truss. I don't think that the bees will try very hard to squeeze into a mass of folded fabric.

[applestar]

Thanks! Great photos and info! I see these metallic bees all the time.
That was really interesting. I didn't realize the little bees collected the pollen on their bellies.

It's funny to think that the comparatively GIANT bumble bees are doing the same thing....

Also, hummingbirds sip at tomato flowers so I guess they also help with pollinating even if just by jostling the flowers.... Do you suppose hummers can induce the flowers to release pollen too

[speedster7926]

TZ when you were talking about bagging them why not pick them if the fruit sets and ripens why not pick it?

[TZ -OH6]

Sure, anything that bumps the flower can make some of the pollen fall out. Its like a salt shaker or flower sifter though, certain frequencies of vibrations are better than othes.

I wonder what the hummers are doing. They really need sugary nectar to keep there hyper metabolism going, and usually get enough protein from the nectar they lick up doing that. They do need bugs for their babies though.

Lots of flowers are adapted to hummingbird pollination but they are usually red tubular things. Christmas cacti are a good example. The anthers will bonk a hummingbird on the forehead every time they stick their beak in one.

[TZ -OH6]

Sorry if I wasn't clear. The bag stays on until
1) All of the flowers have faded
2) The first green fruits get too big to stay in the bag.
3) You need the bag for another plant

In any case the bag comes off when the fruit are still little green things. You don't have to wait until the fruit is 100% ripe to get mature seeds, but they are easier to clean up that way. As long as there is a good bit of gel around the seeds in a green fruit the seeds will grow, but that green fruit is still quite old...long out of the bag.

[Dixana]

Thanks for posting this!! I'm planning on saving seeds from my Krim and my Berkely tie dye this year and have never done it before so I want to make sure it's done right.
I think we should have a sticky just for saving tomato seeds (not that this forum doesn't already have a zillion stickys.....)

[engineeredgarden]

Holy Moly! That's information overload - but I loved every word of it!!! I have an entirely different outlook on the subject now. Thanks!

EG

[garden5]

Excellence, TZ, Excellence.

Definitely sticky material.

[TZ -OH6]

I thought that there was something about tomato seeds in the seed saving-trading forum but it is not in the sticky. That would probably be the best place for it.

I you want a step by step thing I can take pictures of a couple of processes (basic fermentation and the TPS chemical method that is in the potato seed thread) as soon as I get some ripe fruit, but that looks to be at least a couple of weeks off.

For anyone that is ready to save seeds now this is a less disgusting way than the basic fermentation.


1) Halve tomato and squish seeds into a wire strainer.
2) Using a rubber spatula squish and rub much of the juice and gel through the strainer into a container.
3) Add seeds and water to double the volume.
4) Cover loosely and put in warm room temp area for 4 days
5) At the end of four days swirl seeds to be sure the gel has come off (seeds will clump closely together)
6) Rinse, blot dry and fluff up on a paper plate to dry for a few days.


I do several varieties at a time and find that small peices of notecard marked in pencil placed in the goop container work well to keep things organized. Paper tags in the goop will disintigrate.


http://www.flickr.com/photos/51251503@N03/4775551716/

Note in the photo I like to use 16 oz deli tubs, but I did some in ziplock bags that worked fine.

[Dixana]

Excellent information! I would like pictures. I'm a "learn by doing" kind of person and it's easier for me to look at pics and mimic what I see. I also can't get videos to work on my phone

[garden5]

I just has a feeling this would get stickied . Thanks for the through discussion of pollination.

[applestar]

I tried bagging some blossoms. As luck would have it, last weekend, DD's and DH went to the craft store so I asked them to pick up the net bags. There turned out to be 3 different sizes, and not knowing which I wanted, they got some of each size. This has been great, because these unopened (or only one blossom opened) trusses are sometimes tiny or inconveniently placed on a shoot. I ended up using the biggest bag to enclose the entire terminal growth in some cases. I tied the strings to supports and sometimes to the stems so the extra surface area doesn't cause the slender stems to get blown over in the wind. They're flowering now so I've been giving them a tap now and then.

Here are some photos:


With one plant, I had to give up because ALL the flower trusses were at the top of a 7 ft trellis. (I'm going to need a ladder) Yet again, the tomatoes are growing WAY bigger than I expected. I know if I don't get them all tied up and supported properly, there's be a big mess when the first tropical storm of the season blasts through.

[TZ -OH6]

I'll try to post a seed saving "How To" in the seed forum tomorrow. The pictures are ready, but my computer has been out getting devirussed for ten days so I'm just getting back online.

[iseark]

I was going to post and ask how to grow many different tomatoes in my yard without them all getting cross pollinated but found this thread and I THINK I understand what you are saying. The reason for the bags is to stop the pollination so that the seeds that the tomatoes produce will be exactly the same seed you planted, right? So, what I'm wondering is, if the bees do cross pollinate the uncovered flowers will it only affect the seeds of that fruit for the next generation and the fruit itself will be what you planted? I think I said that right. Any help would be appreciated. I'm an avid gardener but just don't understand the whole breeding process.

[Jardin du Fort]

iseark, allow me to quote applestar from a different thread:

Tomato flowers have conical structure of fused anthers called an "anther cone." The pollen is released INSIDE this structure. Excess pollen comes out of the opening at the point of the cone. Most tomato flower's pistil (female receptive part which catches the pollen) does not grow longer than the cone and does not emerge, so that when the flower releases the pollen, it's own pistil catches the pollen and are pollinated.

This means that most of the time, a non-hybrid genetically stable open pollinated or heirloom tomato plant can make uncrossed seeds that are true to type.

Some varieties do have protruding pistil that are more susceptible to cross pollination by wind as well as by insect activity. And insects, especially ones that tear open the anther cone to get to the pollen and maybe nectar too, can introduce pollen from other flowers. I suspect hummingbirds may also have a hand -- beak -- in the process since they visit tomato flowers while visiting my garden.

To be completely sure, I should BAG the blossoms, and I may bag some, but probably not all. Last time I tried bagging tomato blossoms, it was an exercise in frustration. The nylon bags (drawstring wedding/party favor bags) tended to overheat the trusses and/or caused excess moisture humidity, resulting in every truss BUT the bagged ones to set fruit. :evil: I'll try again since obviously, I don't have the technique down. Also, I want to try intentionaly crossing some of these myself by hand pollinating -- and those will need to be bagged to prevent unwanted help by outside sources.

This was earlier this year, and she has obviously used some bags as seen above, so it may depend altogether on just how far out of the flower the pistil protrudes, and whether or not you have pollinating critters....

I guess it all depends on just how sure you want to be that cross-pollination does not occur.