Selective plant crossing? Plant genetics?

[roosterboy]

Well, i was in science class today and they brought up how they make plants stronger, healthier, and larger through genetics.

Of course i am curious. Can anyone explain?

Can i cross my plants?

I had a huge tomato plant but it hardly produced any tomatoes. Is this genetics or was it just because it grew so large?

Can anyone tell me anything else?

Thanks

 

[beavis]

I used to work in a laboratory where we were genetically engineering tomato, brassica napens, vitis vinifera, strawberry and a few others.

We inserted a gene into the host plant's DNA by using Agrobacterium tumefacians.

The gene we inserted helped to delay ethylene synthesis in the plants as the fruit ripened.

Some fruits/vegetables give off ethylene gas as it ripens i.e. tomato, banana, strawberry and by stopping the production of ethylene, the fruit had a longer shelf life.

THAT is one way to modify plants, another method that has been used for centuries is by selecting certain traits in plants that present as desirable, and cross-pollinating that plant and selecting for the presentation of that trait.

 

[beavis]

Here is the abstract from our paper that appeared in Plant Molecular Biology 1994:

We have utilized a gene from bacteriophage T3 that encodes the enzyme S-adenosylmethionine hydrolase (SAMase) to generate transgenic tomato plants that produce fruit with a reduced capacity to synthesize ethylene. S-adenosylmethionine (SAM) is the metabolic precursor of 1-aminocyclopropane-1-carboxylic acid, the proximal precursor to ethylene. SAMase catalyzes the conversion of SAM to methylthioadenosine and homoserine. To restrict the presence of SAMase to ripening fruit, the promoter from the tomato E8 gene was used to regulate SAMase gene expression. Transgenic tomato plants containing the 1.1 kb E8 promoter bore fruit that expressed SAMase during the breaker and orange stage of fruit ripening and stopped expression after the fruit fully ripened. Plants containing the 2.3 kb E8 promoter expressed SAMase at higher levels during the post-breaker phases of fruit ripening and had a substantially reduced capacity to synthesize ethylene.

 

[vfem]

Wow... can I say this takes the Birds and the Bees to a whole new level! Ok, maybe not that new.... but WOW!

 

[Rosalind]

Plant breeding is the same principle as evolution: You pick the biggest, healthiest plants that survive, say, a Fusarium wilt infestation, and cross them. You plant the seeds from that cross, then subject them to another Fusarium infection, and select again only the ones that survive and are healthy. Once you're confident you've got Fusarium-resistant plants, you cross them with plants that have some other desirable trait (e.g. good quality fruit), and infect them with Fusarium again to make sure the hybrids are also resistant.

Why any specific plant is the way it is, can be due to genetics but more often is due to growth conditions.

For example, let's say a plant has a gene to grow very tall, but in the spring it doesn't get enough water. That plant will not grow tall no matter what its genes tell it to do, because of the lack of nutrients.

 

[roosterboy]

Okay, so how exactly do i cross them if they are outside?

Thanks for the answers

 

[Rosalind]

Once they set flower buds, you cover the flower bud with a paper or plastic bag. Then when the other plant also has flowers, you take the bags off both plants and use a Q-tip or a small clean paintbrush to transfer the pollen between the flowers. Then you tie the bags back on the pollinated flowers and wait. The fruit inside the bags should be a cross between the two. You collect the seeds from the fruit, and plant those, that's your cross.

 

[roosterboy]

Can i do this with tomatoes? What are some good plants to learn how to do it?

 

[beavis]

Can i do this with tomatoes? What are some good plants to learn how to do it?

tomatoes are self-pollinating, so not a good choice to start with

 

[Rosalind]

Squash/Cucumbers are easy.

You could try tomatoes, just not all of the resulting seeds will be the hybrid. You have to be sort of on top of tomato flowering times and pollinate them as soon as the flowers open.