Why would some cross an F5 with an F2?

[Cobra50]

@99PerCent

My guess is they double back to isolate a particular trait

@99PerCent, that would make sense. I was reading this GrowFAQ:

What is an F1, F2, and IBL?

What is an F1 hybrid? Posted by Vic High on February 13, 1999 at 22:09:27 PT: This page isn’t about ego trips and pissin contests to see who knows the most. It’s meant to be about sharing info and furthering our understanding of cannabis genetics. So here’s a step in the right direction. Anyone else want to join in? What really is an F1 cross? Well defining the terms P1, F1, F2, homozygous, and heterozygous can be a simple task, however, applying them to applied genetics can often create c…

The writer, @SubCool, confused the living hell out of me. He stated this:

@Subcool

F2 crosses are the offspring of crossing two F1 hybrids. This means that they will not be uniform nor will they breed true. However, F3, F4, F5, etc will also share these characteristics

@Subcool

F2 hybrid - is the offspring of a cross between two F1 plants (Clarke). What Clarke and other sources don’t make clear is do the two F1’s need to be from the same parents? By convention they don’t. As well, german geneticists often describe a backcross of an F1 back to a P1 parent as a F2 cross.

@Subcool

F2 crosses are the offspring of crossing two F1 hybrids. This means that they will not be uniform nor will they breed true. However, F3, F4, F5, etc will also share these characteristics, so to simplify terminology for the seedbanks and seedbank merchants, they can all be classified as F2 seeds in general.

These statement leads me to believe that the F2 doesn’t need to involve an original parent, just a breeding of 2 F1 offspring. This makes a lot of sense to me. Wouldn’t the breeding using the original parents be an IBL? Shouldn’t the designation be IBL F2 for a second generation using an original parent?

It also leads me to believe that an F2 is less consistent (homozygous) in it’s growth than an F1. In this thread, @Subcool states that an F1 will be more consistent than an F2:

@Subcool

The F2 generation is NOT going to produce the same results as the F1 in terms of the similarity of the plants in the group, they will vary in their characteristics rather than all of them being essentially identical. Such a scam rips off the buyer expecting a uniform crop

@Subcool

Now both F1s and F2s are valuable in their own ways, but generally speaking one would need less F1 seeds than F2 seeds to find what they are looking for. Therefore F2 seeds should be priced lower than F1s. Also, anyone under the sun could make quality F2s from a relatively small number of F1s so this should also affect the pricing by lowering it.

@Subcool

It’s a tough call to decide what should be priced higher but supply and demand will probably dictate that a true F1 will be the highest priced seeds. Then the IBLs, followed by the F2 seedlines.

@Subcool’s post contains a list of references, which leads me to believe he is correct in his statements:

@Subcool

REFERENCES:

Clarke RC. 1981. Marijuana Botony Ronin Publishing, California
Colangeli AM. 1989. Advanced Biology notes. University of Victoria, BC
Futuyma DJ. 1986. Evolutionary Biology Sinauer Associates, Inc. Massachusetts
Klug & Cummings. 1986. Concepts of Genetics 2nd ed. Scott, Foresman, & comp. Illinois
Grossnickle & Russell. 1989. Stock quality improvement of yellow-cedar. Canada-BC Forest Resources Developement Agreement (F.R.D.A.) Project 2.40
Watts. 1980. Flower & Vegetable Plant Breeding Grower Books, London
Wright JW Introduction to Forest Genetics Academic Press, San Francisco

I am going to need to get deeper into “Marijuana Botany” on this subject.