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f1 math
- Thread starter CannaZen
- Start date
Hookahhead
Active member
Sorry to say but it looks like your math is all f’d up.
B
Benny106
The plants dont care they just want to live.
imo it's kind of irrelevant how exactly you call it, in the end it's just a definition. it can help you better predict/think about what you get, but just think logically, don't get stuck on a definition too much. the dna/genetics don't know wether you call them f1, f2, polyhybrid or double cross, they're just going to do what genetics do, segregate.
but, going on definitions, there are some things said that I want to comment on.
for onee the double cross-thing. I know this term in relation to maize F1 hybrid breeding, and for that I think you have to know a bit of basics of the history there for why it's a term to begin with and what kind of situation it describes.
an F1-hybrid is not the same as just any f1. any 2 plants crossed together(that are not sisters/brothers or clones) will get you an f1. f1's can be uniform, but don't have to be, it all depends on the parents.
but an F1-hybrid is a specific thing where you cross 2 highly inbred lines together, preferable carefully selected so that these lines have good combining ability with eachother etc. by doing this you get the benefits of heterosis(no inbreeding depression, hybrid vigour), yet also uniformity, every plant from that batch of seeds is the same. and as a breeder you protect your variety since anyone trying to reproduce it will end up with segregating progeny again. so if they want the good stuff, they'll have to keep buying it from you each time again.
now getting a line so inbred to make it work like that can lead to inbreeding depression. especially in a natural outbreeder like maize, or cannabis.
so, in historical maize breeding, when they first tried this method they ran into the problem that their parent lines ended up being such inbred runts that it was not economically viable to sell F1 hybrid seed. the parents just were not fertile and vigourous enough, so they could make the seed, but it would end up so expensive no one would want to buy it, despite the benefits over 'regular' varieties.
so what they did was make those double cross hybrids, so that the parental lines got back some of their vigour and fertility from the first cross, and then the 2nd cross yielded the seed for sale. the final hybrid is not as good(on uniformity+vigour) as a single cross, true F1 hybrid, but it was a compromise with economics in mind. eventually lines were developed which were inbred and still fertile/vigourous enough to make plenty of seed, so now you just see single-cross F1-hybrids.
so that's a really different kind of situation as what we've got with weed. with weed there is a lot of outcrossing, and what I often see called ibl's are just varieties inbred enough to stabilise their traits, but not the high level of inbreeding you'd use to create lines for an F1-hybrid. for that it's not just about stabilising traits, you want a line that is mostly homozygous, which is likely to go together with inbreeding depression in an outbreeder.
the situation with weed I'd compare more to fruit trees breeding. apples for example(although apple genetics are a bit more complicated which play a role too), they just get outcrossed all the time, and the good ones are selected and cloned. no stabilisation needed since you can just grow clones and never deal with seeds again. difference is that with fruit trees a single generation takes years, so even more reason to just not bother with taking it to a higher f-generation, stabilising in that case is just a big waste of time and money. just sell clones and you're done.
and in such a situation, you still call a cross between 2 unrelated plants an f1, but it would not have the typical characteristics you'd know from basic genetics, which assume stable parents. instead, you'd already get a large variation within the f1. and if your goal was to just find a good clone, you could just do your selection on the f1, no need to take it to f2.
but it all depends on the goal you have in mind. if you want to work with seeds it's a whole different game than if you would work with clones only.
another thing I'd like to comment on is about backcrossing. backcrossing can be a real nice tool for certain goals. but if your recurrent parent in backcrossing is not stable, you could backcross it all you want, no matter if it's 6 or 50 generations, it won't become stable. now whether you should care about that again depends on what your goal is, if you just want to introgress one gene from an unrelated line you could just do stabilisation after backcrossing, but backcrossing is not a replacement for inbreeding. they're 2 different tools with different uses. if you want it stable, and it is not stable already, you will have to work on that either before or after the backcrossing.
also, you always have to follow up backcrossing with 1 generation of selfing or fillial inbreeding, otherwise your introgressed gene(s) will end up heterozygous, and so it won't be stable/fixed in the progeny. (again exception could be a case where the gene is dominant and you'd only want to produce clones, since in that case as long as it is expressed it's fine and it does not need to stably inherit)
but, going on definitions, there are some things said that I want to comment on.
for onee the double cross-thing. I know this term in relation to maize F1 hybrid breeding, and for that I think you have to know a bit of basics of the history there for why it's a term to begin with and what kind of situation it describes.
an F1-hybrid is not the same as just any f1. any 2 plants crossed together(that are not sisters/brothers or clones) will get you an f1. f1's can be uniform, but don't have to be, it all depends on the parents.
but an F1-hybrid is a specific thing where you cross 2 highly inbred lines together, preferable carefully selected so that these lines have good combining ability with eachother etc. by doing this you get the benefits of heterosis(no inbreeding depression, hybrid vigour), yet also uniformity, every plant from that batch of seeds is the same. and as a breeder you protect your variety since anyone trying to reproduce it will end up with segregating progeny again. so if they want the good stuff, they'll have to keep buying it from you each time again.
now getting a line so inbred to make it work like that can lead to inbreeding depression. especially in a natural outbreeder like maize, or cannabis.
so, in historical maize breeding, when they first tried this method they ran into the problem that their parent lines ended up being such inbred runts that it was not economically viable to sell F1 hybrid seed. the parents just were not fertile and vigourous enough, so they could make the seed, but it would end up so expensive no one would want to buy it, despite the benefits over 'regular' varieties.
so what they did was make those double cross hybrids, so that the parental lines got back some of their vigour and fertility from the first cross, and then the 2nd cross yielded the seed for sale. the final hybrid is not as good(on uniformity+vigour) as a single cross, true F1 hybrid, but it was a compromise with economics in mind. eventually lines were developed which were inbred and still fertile/vigourous enough to make plenty of seed, so now you just see single-cross F1-hybrids.
so that's a really different kind of situation as what we've got with weed. with weed there is a lot of outcrossing, and what I often see called ibl's are just varieties inbred enough to stabilise their traits, but not the high level of inbreeding you'd use to create lines for an F1-hybrid. for that it's not just about stabilising traits, you want a line that is mostly homozygous, which is likely to go together with inbreeding depression in an outbreeder.
the situation with weed I'd compare more to fruit trees breeding. apples for example(although apple genetics are a bit more complicated which play a role too), they just get outcrossed all the time, and the good ones are selected and cloned. no stabilisation needed since you can just grow clones and never deal with seeds again. difference is that with fruit trees a single generation takes years, so even more reason to just not bother with taking it to a higher f-generation, stabilising in that case is just a big waste of time and money. just sell clones and you're done.
and in such a situation, you still call a cross between 2 unrelated plants an f1, but it would not have the typical characteristics you'd know from basic genetics, which assume stable parents. instead, you'd already get a large variation within the f1. and if your goal was to just find a good clone, you could just do your selection on the f1, no need to take it to f2.
but it all depends on the goal you have in mind. if you want to work with seeds it's a whole different game than if you would work with clones only.
another thing I'd like to comment on is about backcrossing. backcrossing can be a real nice tool for certain goals. but if your recurrent parent in backcrossing is not stable, you could backcross it all you want, no matter if it's 6 or 50 generations, it won't become stable. now whether you should care about that again depends on what your goal is, if you just want to introgress one gene from an unrelated line you could just do stabilisation after backcrossing, but backcrossing is not a replacement for inbreeding. they're 2 different tools with different uses. if you want it stable, and it is not stable already, you will have to work on that either before or after the backcrossing.
also, you always have to follow up backcrossing with 1 generation of selfing or fillial inbreeding, otherwise your introgressed gene(s) will end up heterozygous, and so it won't be stable/fixed in the progeny. (again exception could be a case where the gene is dominant and you'd only want to produce clones, since in that case as long as it is expressed it's fine and it does not need to stably inherit)
Treevly
Active member
New Math?
The red delicious apple was found growing in a farmers apple orchard. He tried to kill it but it kept growing so he let it. Back then apples were sour. He sold the tree for $5,000 all red delicious apples are clones of the original.
Actually Johnny apple seed planted apples to be used to make cider and Apple jack. It’s made by freezing cider and removing the frozen water leaving 35% alcohol. That’s why people would buy Johnney
Actually Johnny apple seed planted apples to be used to make cider and Apple jack. It’s made by freezing cider and removing the frozen water leaving 35% alcohol. That’s why people would buy Johnney
Bottom line is that an F1 hybrid is produced from 2 parents that have been deemed "stable" for a particular set of characteristics.
A lot of people talk about the term stable but 95% of the time they don't define what a paticular seed line is stable for (what a line will breed true for).
Most regular lines these days are unstable multi hybrid lines that are made by crossing F1 male with F1 female parents. Technically speaking, the seed resulting from such a cross would not be considered a true F1 because the parents weren't "strained" (for lack of a better term) to produce a true breeding line.
As far as hobby breeding goes... disregarding the true breeding aspect... a cross from 2 different seed lines would be considered an F1. A sibling cross from that seed line would be F2 and so on and so forth until another line is added into the mix. Then the F1, F2 starts over.
To make things even more confusing, some breeders call a back cross another filial generation such that AxB=F1 and (AxB)xA or (AxB)xB=F2.
In the end, and as already mentioned, the plants don't care what you call them so long as they get a chance to grow.
