Author Topic: Capsaicin  (Read 512 times)

equant

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Capsaicin
« on: 2018-10-29, 11:26:45 AM »
I've never bred hot peppers, and am curious.  How can I expect the traits for heat to show up.   Does the capsaicin show up in the seed produced from a cross, or do you have to wait for the F1 plant to grow fruit to determine the heat of a cross?

naiku

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Re: Capsaicin
« Reply #1 on: 2018-10-29, 05:01:49 PM »
I've heard that the F1 is supposed to be hot, but my crosses have been between sweet peppers and sweet peppers, or hot peppers and hot peppers (as far as I can tell).

Oxbow Farm

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Re: Capsaicin
« Reply #2 on: 2018-10-29, 05:13:22 PM »
The seeds don't actually express any heat as far as I know.  All the heat in a pepper is produced by the maternal tissue, so there would not be any change in heat in the pepper containing the crossed seeds, they would be the normal heat of whatever the mother variety was.

Mike Jennings

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Re: Capsaicin
« Reply #3 on: 2018-10-30, 10:22:09 AM »
I'm assuming that capsaicin production is a quantitative trait, which is why peppers have such a wide range of heat levels. I have read that a higher capsaicin level is dominant in crosses. So, a cross between sweet and hot will be hot in the F1, and will segregate out to roughly 75% hot; 25% sweet in the F2. I don't know if this ratio would be affected by the heat level of the hot pepper in the cross. I don't have firsthand experience with this, but I made some hot x sweet crosses this year, so I will have to report back.

I have noticed, that in crosses between 2 mildly spicy peppers, many F2 plants seem to be hotter than either of the original varieties. I don't totally understand why this happens. My guess is that perhaps there are some recessive genes that suppress capsaicin production to some extent, and these get turned off in the genetic recombination. I need to read up on this a little more.     :)

The capsaicin glands are in the placenta of the pepper fruit (the white part that the seeds are attached to). If you were to go into your hot pepper seed packets and start tasting the seeds, they would probably taste hot, but I think this is just because the capsaicin leaks onto them as the fruit ripens.
« Last Edit: 2018-10-30, 11:22:21 AM by Mike Jennings »

Dominic J

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Re: Capsaicin
« Reply #4 on: 2018-10-31, 12:18:25 PM »
I'm assuming that capsaicin production is a quantitative trait, which is why peppers have such a wide range of heat levels. I have read that a higher capsaicin level is dominant in crosses. So, a cross between sweet and hot will be hot in the F1, and will segregate out to roughly 75% hot; 25% sweet in the F2. I don't know if this ratio would be affected by the heat level of the hot pepper in the cross. I don't have firsthand experience with this, but I made some hot x sweet crosses this year, so I will have to report back.

I have noticed, that in crosses between 2 mildly spicy peppers, many F2 plants seem to be hotter than either of the original varieties. I don't totally understand why this happens. My guess is that perhaps there are some recessive genes that suppress capsaicin production to some extent, and these get turned off in the genetic recombination. I need to read up on this a little more.     :)

The capsaicin glands are in the placenta of the pepper fruit (the white part that the seeds are attached to). If you were to go into your hot pepper seed packets and start tasting the seeds, they would probably taste hot, but I think this is just because the capsaicin leaks onto them as the fruit ripens.

Yes, heat is a quantitative trait, but I think you meant it's an "additive" one.

Without reading on the issue specifically, from the little I know of hot peppers, I must assume it's polygenic trait. It'd be hard to explain such wide variations otherwise.

Raymondo

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Re: Capsaicin
« Reply #5 on: 2018-11-02, 03:13:33 AM »
Yes, heat is a quantitative trait, but I think you meant it's an "additive" one.

Without reading on the issue specifically, from the little I know of hot peppers, I must assume it's polygenic trait. It'd be hard to explain such wide variations otherwise.

A polygenic trait is one explanation for some of the offspring being hotter than either parent.
Ray
Mildly acidic clay loam over clay and ironstone; temperate climate modified by altitude (1000m); avg rainfall 780mm; usually wet summers and dry winters.

Dominic J

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Re: Capsaicin
« Reply #6 on: 2018-11-14, 11:05:48 AM »
Given how wide the scoville ratings will vary, and there are stable varieties all across the board, I'd have a hard time seeing it even possible to not be based on polygenic traits.

If it was just one gene, you'd typically expect to have a cluster around the low value, the high value, and the middle value, at most, for codominant alleles. Or just two clusters otherwise, for recessive/dominant ones. But that's far from the case.

Diane Whitehead

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Re: Capsaicin
« Reply #7 on: 2018-11-14, 12:54:21 PM »
New Mexico State University has an interesting article:   https://aces.nmsu.edu/pubs/_h/H237/welcome.html

Some points I find interesting:

There are more than 22 known capsaicinoids. The major ones, capsaicin and dihydrocapsaicin, normally occur in the highest concentrations.
( I assume there will be genes for each of them.)

environmental factors such as temperature and water influence the heat level. A mild chile pepper cultivar bred for low levels of heat will become hotter when exposed to any type of stress in the field. Conversely, a relatively hot cultivar given optimal environmental conditions will become only moderately hot.
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Doro

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Re: Capsaicin
« Reply #8 on: 2018-11-14, 10:27:31 PM »
I did an experimental cross with sweet pepper x hot pepper.
The F1 was slightly lower in heat, intermediate between the parents in size of the peppers.
The F2 (8 plants) had: 1 plant with no heat, 1 plant with almost no heat (I did not notice heat, but a fried who does not eat spicy food at all said 'it's hot!'), the other plants were noticeably hot in various levels but none reached the hot pepper parent plant. Size of the peppers was small to intermediate, none reached the size of the sweet pepper parent and two were almost as small as the hot pepper parent. Usually high numbers of seedlings are needed to find big ones. Getting size back is always most difficult and often requires back crossing at some point, especially when the parent varieties have a big size difference.
The F3 - F5 derived from the plant with no heat had only offspring that was not hot.

I didn't continue with it further, the flavour was just no good. Bad flavour is really hard to get rid of. I should have picked a better tasting hot pepper variety, just used that particular one for the cross because of its hardiness and low light requirements. It was worth a try.

Dominic J

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Re: Capsaicin
« Reply #9 on: 2018-11-15, 07:05:59 AM »
Heat overall seems polygenic to me, but it's quite possible that, in some peppers, it isn't.

As Diane shared, there are a lot of capsaicinoids, which contribute to heat.

Without knowing for sure if it is indeed the case, it would be theoretically possible that the production of one or many capsaicinoid revolves around a single gene (each). Just as some genes may influence many capsaicinoid, or some capsaicinoid may be regulated by multiple genes. Since heat is an aggregate measure of all of a lot of different molecules, it's very likely that all of that is at play. With hot peppers as a whole.

However, it's also quite possible that some hot pepper strains are much, much more simple. Maybe a particular hot pepper derives heat solely from 1 capsaicinoid, for example. And maybe that molecule is regulated by a single gene. Thus, crossing hot pepper X with sweet pepper Y may give results compatible with the standard codominant distribution. But crossing hot pepper Z with sweet pepper Y may give a completely different  distribution, even if hot pepper X and Z have similar heat, because they might get their heat from different molecules that rely on different genes.

I haven't found much quickly googling the topic, but I'm fairly confident that the subject much have been heavily investigated. There's probably already a bunch of genes identified for heat.

Doro

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Re: Capsaicin
« Reply #10 on: 2018-11-15, 09:55:42 AM »
Capsaicine inheritance is a hat filled with magic worms, there are so many papers about it. Some back each other up, others contradict each other. Results vary a lot and some interactions are still in the dark, or very well hidden in the huge haystack of all those pepper papers.
Most seem to agree that heat mainly follows additive dominance, plus some partially still unknown interaction effects between the various genes for different kinds of capsaicine.
Which leaves non laboratory breeders not much wiser. For me it just mean that I won't know what exactly happens to a specific cross, if I don't try and see. But I do not focus on heat in my breeding projects, it's mostly other traits that are interesting to me. Thankfully much more straight forward recessive or dominant.
My current main pepper project is how variegation interacts with the chlorophyll retention gene in ripe fruit, Fish Pepper meeting Brown Jalapeño. Maybe I'll find striped ripe fruit, then I'll just take any heat they might have. Looking forward to the F2 next summer.

Diane Whitehead

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Re: Capsaicin
« Reply #11 on: 2018-11-15, 05:00:32 PM »
Another possible variation:  when does the heat appear?  I've recently read of two kinds that change
while ripening.

One develops its heat when it ripens to red - can't remember its name.

and, just the opposite:  Aji escabeche, a baccatum from Peru, is hot while green but sweet
and mild once ripe.

Are there others?
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equant

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Re: Capsaicin
« Reply #12 on: 2018-11-19, 10:07:24 AM »
Interesting thoughts and insight from everyone.  Thanks.  Just to add a bit more, I read in a plant breeding book (one recommended in Deppe's book) that fruit size and shape is determined by ~30 genes.

Doro

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Re: Capsaicin
« Reply #13 on: 2018-11-19, 02:09:05 PM »
Fruit size and shape are really a fun thing to experiment with.
I got a really interesting F2 this summer.
The original cross (C. baccatum) was Nepalese Bell x Aji Yellow Russian.
One with a red round baccatum bell shape with relatively thick walled fruit and the other one has a yellow long thin and flat fruit shape.
I was looking for the hardiness and flavour of the Russian variety with fruit that are not a pain to clean from seed - larger and a little fatter.

One picture is a Nepalese Bell fruit with the F1.
The other picture is examples for the F2 fruit. (It is made without filter, it just looks weird because of the dead lawn.)
The yellow line and the orange line will go into the F3 next summer.

Diane Whitehead

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Re: Capsaicin
« Reply #14 on: 2018-11-19, 02:48:38 PM »
Great fun indeed!  You inspired me so I just went out to the greenhouse to see if I have any flowers.  No, just Nepalese Bell fruit.  OK.  Next year I will try for different colours of Nepalese Bells.
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