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deluxestogie

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Stupid question but if a plant cross pollinates naturally do the plants that are growing take on the characteristics of the crossed plants or is it just the seed?
If you are not saving seed, it does not matter if the plants cross pollinate. The presently growing plant is unaltered. Only its seed is crossed.

In the case of a N. rustica and N. tabacum, what would the seeds look like.
Rustica seeds are larger than tabacum seeds. Would that be determined by the female side of the cross?
Or would the seeds be an average of the sizes of rustica and tabacum?
Even with active effort to cross N. tabacum and N. rustica, most attempts fail. When seed is successfully produced, most of it is sterile. I don't know what size seed such a cross would yield.

Bob
 

ChinaVoodoo

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I wonder why it is the seeds would be sterile? Its funny how some things just won't go together even though one would think they would.

Don't misconstrue the fact that I've read this article as evidence I understand it.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2710205/#!po=13.0682

Nicotiana tabacum and N. rustica are both tetraploid. Animals are diploid. We get one set of DNA from each parent. 1+1= "di-ploid", whereas with tobacco, they get two sets of dna from each parent so 2+2= 4 (tetra)ploid.
The thing is, there are tetraploid Nicotiana species and there are diploid Nicotiana species. The tetraploid species arose from the successful mating of diploid species in the wild. Since this happened a long time ago, and because the tetraploids have a lot of extra redundant DNA, they've gradually lost unnecessary parts of it. This helps scientists determine how long ago the species began. They also know which diploids are their ancestors.

mcm32601.jpg

The immediate ancestors of rustica and nicotiana are very different from one another. Their common ancestor would have been millions of years ago. There has just been too much time for them to change both before and after tetraploidization for the plethora of chromosomes to match up in a meaningful manner that when asked to divide again (when making pollen, and eggs), that they would end up not just with useful pairs, but in their case useful quads when they mate (seed stage).
 

Tutu

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Post #34 by ChinaVoodoo has had me interested for a while now. So I was at the airport browsing some pdf's and such, and stumbled on the following. My question really is why the cross would only work ono direction. Why does rustica have the be the female. Now I know the resulting F1 is sterile, but the backcrossing of Deligold to Virginia 115 in China's quote really has my interest. In any way, why the single direction?

"Nicotiana rustica carries resistance to bacterial wildfire diseases, and also fungal black shank, but can only be crossed with N. tabacum when N. rustica is used as a female. However, these F1 hybrids are sterile."

Screenshot_20170522-135952.jpg
 

deluxestogie

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Both Nicotiana tabacum and N. rustica have similar chromosome numbers. This might suggest that the two different species might inter-breed. Both are allo-tetraploids. That is, they have double the diploid number of chromosomes as their putative ancestors. Unfortunately, during that mix-and-match process, the additional copies of various genes are not located in the same places. So when the two species are crossed, the resulting chromosomes are a mess, so to speak.

It is my understanding that "these F1 hybrids are sterile" should instead be stated as "these F1 hybrids are usually sterile." Rarely, you get some seeds that are fertile.

Bob
 

Tutu

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But my question remains. Why does rustica need to be the female in creating the hybrid why wouldn't it work with tabacum as the receiver?
 

deluxestogie

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First, I don't know the answer.

Pollen grains have to accomplish a task that the ova do not. Upon landing on the stigma, a pollen grain must create and grow a pollen tube (an actual tubular extension of the pollen plasma membrane) that penetrates between the cell layers of the pistil, reaches an ovum, and successfully merges its nucleus with the nucleus of the ovum.

Vernonica E. Franklin-Tong. Signaling and the Modulation of Pollen Tube Growth said:
This complex and hazardous process involves many interactions, including cell–cell recognition and intracellular and intercellular signaling, as well as many other factors that remain to be identified.

http://www.plantcell.org/content/11/4/727.full.html
How Pollen Tubes Grow: http://www.sciencedirect.com/science/article/pii/S0012160606014035
Pollen Tube: https://en.wikipedia.org/wiki/Pollen_tube

My guess is that N. tabacum pollen provides chemical signals that are "close enough" to occasionally succeed, whereas N. rustica pollen just doesn't manage to trick the N. tabacum pistil into yielding its resources to what may be sensed as a foreign pollen. (Normally, every pistil is bombarded by pollen from all sorts of different plants. It has to be selective.)

That is to say, the pollen (as opposed to the ovum) requires additional skills. N. tabacum pollen is apparently better at fooling the N. rustica pistil, than the N. rustica pollen is at fooling the N. tabacum pistil.

Bob
 

MarcL

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... Upon landing on the stigma, a pollen grain must create and grow a pollen tube (an actual tubular extension of the pollen plasma membrane) that penetrates between the cell layers of the pistil, reaches an ovum, and successfully merges its nucleus with the nucleus of the ovum. ...

this sounds borderline vulgar. you sure you didn't pull it out of penthouse forum magazine?
 

deluxestogie

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this sounds borderline vulgar. you sure you didn't pull it out of penthouse forum magazine?
Let's be clear. This is explicitly describing plant sex. Flowers are pretty, but they are plant sex organs. Flowers smell nice only for the purpose of coaxing other species to assist them in their sexual activity.

So if this sounds suspiciously sexual, that's because it is sexual.

Bob
 
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MarcL

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Let's be clear. This is explicitly describing plant sex. Flowers are pretty, but they are plant sex organs. Flowers smell nice only for the purpose of coaxing other species to assist them in their sexual activity.

So if this sounds suspiciously sexual, that's because it is sexual.

Bob

My apologies, I meant to say, this sounds explicit. you could write for Planthouse Forum Magazine?
 
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ChinaVoodoo

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https://link.springer.com/article/10.1007/BF00888814?LI=true
According to this research article, ionizing radiation applied to the pollen can aid in pollen tubes' ability to successfully fertilize crosses between rustica and tabacum. This suggests to me that Bob's explanation in post# 49 is exactly right.

Also since I have cobalt 60 and iridium 192 at my disposal at work, it gives me ideas.
 

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So much work stabilizing a hybrid, I wish you guys the best.

What traits would you try to fix in the cross? What features would you like to increase or decrease? Many of the crosses seem straight forward like adding disease resistance. It's simple to attempt to kill off the first gen and save seed from the survivors, maybe rinse and repeat. But with flavors or other compounds you'd need to save every seed from every offspring and sample everything before replanting.

What a huge endeavor.

Jessica has the right idea, gene splicing or whatever it was she was talking about. Bam.

Why aren't you using a crispr kit to make new strains?
 

ChinaVoodoo

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So much work stabilizing a hybrid, I wish you guys the best.

What traits would you try to fix in the cross? What features would you like to increase or decrease? Many of the crosses seem straight forward like adding disease resistance. It's simple to attempt to kill off the first gen and save seed from the survivors, maybe rinse and repeat. But with flavors or other compounds you'd need to save every seed from every offspring and sample everything before replanting.

What a huge endeavor.

Jessica has the right idea, gene splicing or whatever it was she was talking about. Bam.

Why aren't you using a crispr kit to make new strains?

I'm not planning on doing it, personally. I am curious though whether the pollen experiment could be duplicated.
 

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Just finished reading this article. As the title suggests, it is mostly concerned with lethality, not with vitality. It discusses various lethality problems in hybrids within the Nicotiana species and gives suggestions as to how to overcome it. This is the article:

http://cdn.intechopen.com/pdfs/32719.pdf

First thing that was interesting for me was that the problem is not only whether the seeds of crosses between N. tabacum and N. Rustica would germinate in the first place, but also whether they are likely to grow to adults. In case of lethality problems, one way to overvome them is to grow in raised temperatures. That is:
"Hybrid seedlings show hybrid lethality at 28°C, a temperature suitable for the growth of tobacco plants. When hybrid seedlings are cultivated at elevated temperatures generally ranging from 32-38°C, the seedlings may grow normally without exhibiting lethal symptoms."
These symptoms are discussed in an earlier part of the paper. The following is important though:
"However, hybrid seedlings must be cultivated continuously at elevated temperatures from germination to maturity. When hybrid seedlings are transferred from an elevated temperature below 28°C, they will die."
I thought this was interesting to say the least.
 

deluxestogie

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That is interesting, Tutu. It suggest that a key metabolic enzyme is present, but in insufficient quantity to maintain metabolism. The raised temp would increase the activity of the enzyme. It therefore also suggests that the affected enzyme is not part of a metabolic cycle that itself accelerates with increased temp. There are too many possibilities for me to even begin to guess what specific enzyme that might be. An example might be an enzyme that prevents overexposure to high-energy molecules created during photosynthesis.

Both N. rustica and N. tabacum have quadrupled sets of chromosomes from the putative parent species that went to create those modern species. But which genes are located where on the chromosomes differ between N. rustica and N. tabacum, as would be expected from independently evolved crosses. So when crossing those two species to one another leads to viable offspring, it's genetics is similar to combining half a gasoline-powered automobile with half of an electric one, and expecting things to work out. It's a true wonder that it ever does.

Bob
 

OldDinosaurWesH

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Bob:

Stop it! you're making me laugh...crossing gasoline and electric cars...Is that anything like crossing a donkey with a horse?...

On a more serious note. If my memory serves, doesn't modern tobacco have 28 chromosomes. (7 x 4), or was that 32 (8 x 4)? I forget.

On a less serious note, I always like to say that "God makes the laws of physics, and he doesn't explain them to us."

Wes H.
 
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