Wednesday, February 2, 2011
Breeding Tomatoes at Home
6:25 PM | 
Posted by
StepheninKY |
Today I want to try and do a how to on breeding tomatoes for the home gardener. A lot of times I think this subject gets lost in science terminology and really it is not that hard once you get the basics and have done it several times.
A cross is to take two different varieties and combine them to get a new type of variety that has genes from both parent varieties. First let's do a basic run down of the different flower parts and what they do.
Sepals
The sepals of a tomato flower are the outermost structures that enclose the flower and protect it before it opens. Together, the group of sepals is called a calyx. They are connected to a stem part known as the peduncle, and support the rest of the flower.
Petals
Petals are the yellow flaps that contain the reproductive parts of the tomato flower, and recruit bees and birds to become pollinators. As a whole, the petals make up the corolla.
Stamens
The general term for the male reproductive part of a flowering plant is the stamen. The filament, or "stalk," of the stamen stands vertical inside the flower petals. Atop the filament sits the anther, which is responsible for making pollen. In the case of tomato flowers, several stamens are connected and enclose the female reproductive parts.
Carpels
The pistil is the female reproductive structure of a flowering plant. In tomato plants, this green formation can be thought of as a collection of several separate parts knows as carpels, which each contain three parts: The tip of the pistil is called the stigma. The vertical stalk that holds the stigma is the style. The base of the carpel encloses ovaries, or eggs.
Fertilization
Having both male and female parts, tomato plants can pollinate themselves. While cross-pollination is common, normally pollen from the anther of one flower is transferred to the stigma of the same flower. The pollen grain then extends down inside the style to form a tube, which then carries two sperm cells down to one of the ovules. Once fertilized, the ovule becomes one of the seeds of the tomato fruit.
Now that we are more familiar with the parts that make up the flower, let's move on to crossing our tomatoes.
Emasculation (Flower vasectomy)
Flower buds about 2 to 3 days away from opening should be chosen for emasculation. At this stage, the petals slightly jut out of the flower bud and the corolla color is slightly yellow or even paler (basically the flower is still closed but you can just start to see the yellow bloom inside. To emasculate, use a sharp-pointed forceps (Tweezers with pointed ends) to gently force open the unopened bud and the corolla, and then the anther cone. Then, carefully pull the anther cone out of the bud leaving only the calyx, corolla, ovary, and the style. Usually the flower is emasculated from 1 -3 days prior to pollination. Carefully place a cloth bag over the emasculated flower to prevent insects from fertilizing the flower. These can be bought in the craft section at box stores and hobby stores just ask for the small wedding bags.
If you look at the flower parts image to emasculate the flower carefully remove the yellow petals and the stamen being careful not the remove or damage the stigma or ovaries. If you mess up the first few tries welcome to the club. Tomatoes have lots of blooms so keep trying. It's not too hard once you get the hang of it.
Pollen Collection (male parent)
There are many ways to do this but I am going to share the simplest method here. Get a cheap pair of dark sunglasses and pop out one of the lenses. (The dark lens will help you to better see the pollen) Pick an open flower and place the sunglass lens directly under it. Now tap the flower and the pollen should fall and land on the lens. You can also use the back side of an electric toothbrush. The vibrations will cause the pollen to come out and fall to the lens. Collect this pollen into a small container with a lid. Place the container inside so the pollen can dry a little. You can place near a lamp to speed this up if you want. After a hour or two place the top on the pollen container or cover with plastic wrap. Set aside till the next day.
Pollination (the fun part)
Now that you have collected your pollen and emasculated the flower the next step is to actually make your cross. You can use a small paint brush, Q-tip, or your finger. Whatever you use dip it into the container so that the pollen sticks to it. Make sure you get plenty of pollen on the stamen to insure good fertilization of the ovaries. Be careful that you do not damage any of the parts. Cover back up with your cloth bag. Repeat this step over the next three days. You should be able to notice a swelling of the ovary this indicates that the cross was successful. If it does not and the flower is aborted then the pollination did not take. Do not worry about it as it can happen just keep trying. Once the fruit is setting then you can remove the bag. You need to make sure to mark the stem so that you know it's the crossed fruit. You can use a loosely tied string or something similar. Just make sure whatever you use is not too tight and it can hold up to the elements.
Harvesting
The duration from pollination to fruit ripening is about 45 days but could vary depending upon cultivars and season. In warmer climates, plant development tends to be more rapid than under cooler conditions. The pollinated fruits should be kept on the plant until they become fully mature, preferably at least in till they blush. (Meaning that they have at least started to turn their final color)
OK, so now that you know how to cross tomatoes, what comes next?
If you grow out your crossed seeds you will have a hybrid tomato. The cool part about hybrids is that any time you cross the same two different varieties the hybrid plants will always be the same and each of the hybrid plants will be genetically identical.
This means if you cross two heirlooms say Brandywine X Black cherry tomato then grow out the hybrid and really like it, then you can always go back and make the cross again and get the same hybrid again. Also seed is good for many years so you can use any leftover seeds to grow the hybrid again as well
Now if you grow out seed of the hybrid plants the pants will be different from each other and you can pick which ones have characteristics you like and continue trying segregate them into a new variety.
Hybrid (f1) Frist generation after the cross
F2 second generation plants will have variations from each other pick the plants you really like something about and save the seed.
F3 third generation continue to select plants that have characteristics you like and save seed
F4 –F8 At around F5 to F8 the plants from seeds will start to have little to no variation meaning that the plants will have the same characteristics and are a new variety. Congratulations you have just breed your very own variety of tomato and have every right to give it any name you want. Just if it is really a good one make sure you send me some seeds J LOL
Again hope you folks enjoyed the blog and learned something new. Please feel free to post comments, suggestions for future blog topics, or really anything you want to say lol
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About Me
- StepheninKY
- Hello, My name is Stephen and I live in Kentucky. I also love gardening. I guess you could call it a bit of a hobby. I figure as far as hobbies go it is a pretty rewarding one. There is nothing in the world better than growing and eating just about anything you grew yourself.
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