Breeding chillis: any good links,books,etc.?

[Nike]

As my plants are starting to flower I was thinking about cross-breeding them and maybe trying to end up with some new variety. But as all these F1`s, F2`s are complete mysteries to me,I would be very interested in any info about how it works. I`m also curious how you stabilize what you`ve created,so that all the seeds will turn out a same kind of plant.

[TheBigX]

Well those F-things are quite simple. They tell which generation plant we are talking about:
P, parenta=the original plants (eg. C. chinense x C. annuum)
F1, filos 1=the first generation of hybrids (result of the crosspollination of P-generation plants)
F2, filos 2=the second generation of hybrids (result of the crosspollination/selfpollination of F1-generation plants)
etc.

I believe you stabilize a variety by selfpollinating it for 3-4 generations. This makes genetic variation between selfpollinated seeds very limited and therefore the seedlings can be considered the same variety. In practice this is done by choosing the best one of the F1-hybrids and selfpollinating it, choosing the best one of the F2-hybrids obtained this way and selfpollinating it, etc.

[Nike]

But what about all these recessive and dominant traits of the plants? (Are those the right terms?) I`ve gotten the idea that some traits that show up in the F1 generation won`t show up in the F2 etc.? It`s quite a confusing area  :?

[Omskakas]

But what about all these recessive and dominant traits of the plants? (Are those the right terms?) I`ve gotten the idea that some traits that show up in the F1 generation won`t show up in the F2 etc.? It`s quite a confusing area  :?

Most self pollinated varietes are 'stabilized' which means that most, if not all its alleles are homozygous. So there is no genetic variation within the variety, which means that every generation looks the same. But different varietes usually have different homozygous alleles. If you cross different varietes, you get many alleles that are actually heterozygous. The idea to cross different varietes is to achieve heterosis. This is why many commercial varietes are F1 crosses. Heterosis makes them more vigorous and productive!

However, if you want to 'stabilize' F1 variant, you have to self pollinate it several times. In each self pollination (F1 --> F2 etc.) variety loses 50% of its heterozygous alleles. Remember that in those heterozygous alleles one is from each parent. When alleles become homozygous again, you lose genetic variation and maybe vigor and productivity too. Each time variety loses heterozygous alleles it turns somewhat different. Different branches of same F1's children might turn out very different depending on which alleles they get from P1 & P2 plants and which not. So, you can't stabilize F1 'as it is'.

Edit: Genetic dominance isn't that important in crossings IMHO, but you can read it from here: http://en.wikipedia.org/wiki/Dominance_relationship

[TheBigX]

Okay, that's not quite so easy to explain.

So let's just start of with a simple example. Let's say we have a red cayenne and a yellow cayenne and let's assume that the colour of the pepper is determined by only one chromosome. Chromosomes are smaller parts of which DNA is built from. A human, for instance, has 23 pairs of chromosomes, making humans a diploid species. Many plants, too, are diploid, whereas the plant always has two of each chromosome (let's just assume that all plants are diploid here). So basicly there are two sets of chromosomes, two strings of DNA, of which both contain the same types of chromosomes, giving the DNA two possible blueprints. One of these strings is inherited from the male parent and the other from the female. Since you can have two different kinds of one certain chromosome (one chromosome always controls a certain set of features, the place of the chromosome in the DNA string determines which ones), one of them is stronger, being the dominant, making the other one weaker, recessive. If the DNA of an individual contains both a dominant and a recessive chromosome, only the dominant will be visible in that particular individual and the recessive will remain dormant. However if both chromosomes are the same (even recessive), that particular feature will be visible.

Now let's explore the colour of the peppers. Let's say the red colour is a dominant feature and yellow is recessive. This means that the yellow parent must have two of the yellow, recessive chromosome. The red parent however, can have both two red, dominant, chromosomes or one red and one yellow. Let's say this individual has two red ones.

So the P-generation is:
Yellow parent: yy (two sets of yellow, a non-capitalized letter represents a recessive feature and the letter is always the first letter of the recessive feature)
Red parent: YY (two dominant chromosomes)

What are the possible outcomes in the F1-generation (each parent gives one of the possible chromosomes, both have equal chanses to be "chosen")?
---y--y
Y-Yy-Yy
Y-Yy-Yy

This table shows that we get 4 hybrids of identical colour, all of them red, but they have also the yellow chromosome hidden.

The F2-generation looks like this:
---Y---y
Y-YY-Yy
y-Yy-yy


So here we get three red and one yellow, of which one only has the red chromosome, two are red, but also have the yellow chromosome and one is completely yellow.

I hope this example clears it up a little bit...

[Nike]

Thanks guys, that did add to my confusion  

No, seriously; when you want to stabilize a strain you`ve created, one must then always choose the individual plants that most closely resemble what you want,yes? But when you have, for example, "Habanero Chocolate", and you just grow it with no special attention to breeding, it self pollinates and if you then save the seeds and plant them again,will it make the next generation weaker than the plant the seeds came from? I mean, when you have a stabilized strain,how come it survives year after year without being finally killed by inbreeding? :?

[luca]

Cool topic!

This is a really interesting (and complex) subject, but it is quite logic (when things are simplified, of course).

I remember my father saying, when I was learning blood types and stuff at high-school, "This is dangerous! Suddenly the kids find out that their father can't really be their father, because of their types of blood!" :lol:

[TheBigX]

No, seriously; when you want to stabilize a strain you`ve created, one must then always choose the individual plants that most closely resemble what you want,yes?

Quite so. This way the following generations will slowly start to get completely identical (both strains of DNA identical).

But when you have, for example, "Habanero Chocolate", and you just grow it with no special attention to breeding, it self pollinates and if you then save the seeds and plant them again,will it make the next generation weaker than the plant the seeds came from? I mean, when you have a stabilized strain,how come it survives year after year without being finally killed by inbreeding? :?

No, it will not become weaker. In most cases it will be very much like the parent. Of course it's possible that it gets weaker due to bad mutations or such.

Inbreeding is not a problem with plants. Their genetic properties don't weaken as a result of inbreeding, unlike with animals. I have no idea what makes this a problem with animals, but that's just the way it is. In the plant kingdom those things that are quite deadly to animals can be very beneficial. Some of the most resistant, quickly growing and highly fertile plants are actually triploid or polyploid, whereas this is quite a problem with humans (this is the cause of many very serious genetic diseases).

[Omskakas]

But when you have, for example, "Habanero Chocolate", and you just grow it with no special attention to breeding, it self pollinates and if you then save the seeds and plant them again,will it make the next generation weaker than the plant the seeds came from? I mean, when you have a stabilized strain,how come it survives year after year without being finally killed by inbreeding? :?

No, it will not become weaker. In most cases it will be very much like the parent. Of course it's possible that it gets weaker due to bad mutations or such.

If there is sexual reproduction, recombination can still eliminate harmful mutations. In self pollinated plant sex is sex even if you have it with yourself.  :wink:  However, if you take cuttings over and over again from same plant(clone) lineage and there's no sex in between, the clone will eventually die because of mutation accumulation.

Inbreeding is not a problem with plants. Their genetic properties don't weaken as a result of inbreeding, unlike with animals. I have no idea what makes this a problem with animals, but that's just the way it is. In the plant kingdom those things that are quite deadly to animals can be very beneficial. Some of the most resistant, quickly growing and highly fertile plants are actually triploid or polyploid, whereas this is quite a problem with humans (this is the cause of many very serious genetic diseases).

It's true that polyploidy will protect plants from harmfull mutations in some extent, but they do suffer from inbreeding also. Species and populations that have a (long) history of inbreeding suffer less because they have less recessive harmful mutations in their genome (inbreeding has already eliminated most of them). Most monoeciuous plants (eg. chiles) don't suffer much from inbreeding because they are already highly inbred because of self pollination. In animal kingdom there are also species that don't mind much of occasional inbreeding (eg. Finnish moose population) and those that do suffer from inbreeding (eg. birds that have big panmictic populations).

[Nike]

Where did you guys learn all this? Any good books on the subject?

[Omskakas]

Where did you guys learn all this? Any good books on the subject?

Five years in university studying biology and botany might have done the trick for me.  :wink:

Campbell and Reece have written a book called 'Biology' which might be a good place to start. The book contains a lot from almost every field of biology.

[TheBigX]

Well what I know is really elementary genetics, which is part of course two (obligatory course) in high school biology. So in just about 36 hours at school you can learn quite a lot of interesting things!

[Nike]

Well what I know is really elementary genetics, which is part of course two (obligatory course) in high school biology. So in just about 36 hours at school you can learn quite a lot of interesting things!

That is: IF you were listening

[maxpowa]

Campbell and Reece have written a book called 'Biology' which might be a good place to start. The book contains a lot from almost every field of biology.

Same goes for Biology By Julian Sutton, published by MacMillan foundations, ISBN 0-333-65860-4

[NaokiSoma]

So the P-generation is:
Yellow parent: yy (two sets of yellow, a non-capitalized letter represents a recessive feature and the letter is always the first letter of the recessive feature)
Red parent: YY (two dominant chromosomes)

What are the possible outcomes in the F1-generation (each parent gives one of the possible chromosomes, both have equal chanses to be "chosen")?
---y--y
Y-Yy-Yy
Y-Yy-Yy

I'm not a master in biology. Could someone tell me, if these chances in getting all possible combinations will happen

a) one combination for every seed (every seed has equal chance of having different genes)
b) one combination for every pod (every seed in same pod would have same genes)

This would in chase a) make things difficult for choosing the best properties for a plant to the next generation. It would be more like a lottery.
In chase b) it would be easy to taste/visualize the pod to decide the best one.

I have a feeling that nature is closer to the a). Is it true?