Just trying to understand exactly what an F1 hybrid is.
Is it a first generation hybrid species derived from crossing one native species with another native species of separate origin? ie: r. gallica x r. rugosa – or something like that anyways?
Do I have it right?
Is F2 a second generation hybrid species?
And why the letter ‘F’?
Sorry, I think I found my answer, though; I didn’t think it has so many definitions
“First filial” and “second filial” - filial meaning “offspring” or “generation”, essentially.
I think some of those definitions are excellent; others, like the first two, are referencing somewhat limited connotations that the original term was almost certainly not meant to convey. For instance, in its purest sense, an F1 is simply the first generation of any cross between related, but not identical (and not F1) individuals. It doesn’t necessarily follow that there will be hybrid vigor compared to “ordinary hybrids” (I would consider that an invalid point; besides, there is no such thing as an “ordinary hybrid”). Referencing definition number two, the parents are necessarily related, or else they would not cross at all. At least the third definition, although it is limited to a somewhat specific commercial connotation, is trying to put it into that context.
The F2 is simply the generation that follows when you cross F1 offspring with one another.
Thank you Stefan, much appreciated 
Stefan - Turns out I
Hi Dee,
I think that the simple definition is that an F1 is a cross between 2 unrelated parents. Generally when a plant breeder means unrelated they only are going back one generation in the pedigree.
So take for example Peace, it was the pollen parent of Karl Herbst (seed parent was Independence). Peace was also the pollen parent of Iobelle (seed parent was Dean Collins). If either Iobelle or Karl Herbst were crossed to Peace the offspring would be referred to as the backcross 1 generation (BC1). Karl Herbst and Iobelle are considered half-sibs since they have one parent in common, but if you crossed them together most breeders would consider that to be a modified F1, or a half-sib cross. If you collected hips from Peace and you knew that they were all self pollinated hips, the ofspring from those hips would be considered F2 plants.
Clear as mud, eh? Hopefully I have not added to the confusion.
Liz
Hi Liz, yes, I think it’s clear. You state the parents of an F1 hybrid must be unrelated by one generation. A few more complex quesitons if you please…
Therefore an offspring would not be F1 if both parents were sibs (not half), with three or more grandparents in relation, correct?
Let’s pretend that Karl Herbst was the result of a self- pollinated Peace instead. Karl Herbst is then crossed with Iobelle. The offspring would not be F1, correct?
Stefan states: F2 is simply the generation that follows when crossing F1 offspring with one another (F1 x F1).
So what if both F1’s are half-sibs; would their offspring be a modified F2?
The offspring of a self-pollinated Peace is classified as F2, but I don’t understand how.
Do I ask too many questions, lolol!?
Whew!
Hi Dee,
Well here is where things get complicated again. An F2 in the plant world is through selfing or in other words mating of genetically identical parents, clones. So if you had 2 Peace plants and you crossed them that would be an F2. When breeders cross varieties that have some common parentage together such as Karl Herbst by Iobelle, it is referred to as line breeding.
Offspring of a self pollinated Peace are considered F2s because Peace is a F1, the result of crossing 2 genetically different plants.
Liz
To make things simple.
We use F1 and F2 for roses that are vegetatively propagated clones. This extended use means then crossed first generation hybrid and selfed or sibbed second generation hybrid. Often a mix of both. No more!
Usually theses F1 and F2 terms apply for seed grown crops such are Tomatoes, Corn or Petunias. The F1 are uniform seeds from crosses one can get only from true breeding parent lines or vars.
Highly inbred then means selected for being uniform and true breeding through many generations of selfing and selecting.
Unlike an hybrid of clones that is breeding all different progenies we are looking for.
An F2 in the plant world is through selfing or in other words mating of genetically identical parents, clones.
Liz, does ‘selfing’ not also include self-fertilization, meaning the plant fertilizes itself with its own pollen (as opposed to crossing two genetically identical parents)?
Is ‘selfing’ considered vegetative propagation?
We use F1 and F2 for roses that are vegetatively propagated clones. This extended use means then crossed first generation hybrid and selfed or sibbed second generation hybrid. Often a mix of both. No more!
Now that flies over my head 
I’m not sure I understand what you’re trying to say. First of all, Liz has just established that a ‘clone’ is the result of mating two genetically identical parents. So I don’t see how F1 could possibly be a clone also.
Dee, I think that you are mis-understanding my response. For roses, the only way we can have 2 genetically identical plants is to clonally propagate them, rooting cuttings or grafting. Selfing is self-fertilization which is the most rapid form of inbreeding. Collecting self-pollinated hips from Peace is the same thing as collecting hips from Peace that have been pollinated by Peace.
Pierre is absolutely correct about how these terms generally DO NOT apply to roses, but instead apply to crops where inbreeding is used to reach homozygosity. These crops are not vegetatively propagated, instead they are propagaed via seed.
Liz
O.K. Liz, it makes ALOT more sense now; I see where I went astray. I don’t want to make things more complicated than what’s already been explained. Thank you for taking the time to clarify it all
Dee.
Dee, not a problem. I have a colleague, soybean breeder, that had a hard time grasping how roses were propagated when we took a bunch of grad students down to visit Joyce Fleming last fall. He was convinced that we had to self them until they were homozygous. Each crop uses its own set of jargon just a bit differently. Can make things more than a bit confusing.
Liz