Do you undestand the difference between mutation and evolution?
Yes, ma'am.
And I have told you point mutation RhT-B1 is not an example of evolution. ... The dwarfing is a natural gene (trait) that is selected by the plant breeder.
[All emphases mine.]
Whether or not it's an example of evolution, at least here you quietly concede that
Rht-B1b is a mutation. Originally, you said it wasn't: "Dwarf wheat was developed ‘through traditional cross-breeding techniques, utilizing naturally occurring dwarf genes’ (quote from article). It isn't a mutation ..." (
source). "Dwarf wheat ... is not a mutation" (
source).
(It is worth pointing out that the article she quoted—for which she didn't provide the source—said that these dwarf genes were "naturally occurring." Naturally occurring means not induced.)
[The mutation of Rht-B1] is an example of gene manipulation and induced mutations, but those mutations did not evolve and will not evolve. Dead ends.
I think there might be some equivocation with the term "evolve" here, because these mutations certainly did evolve somewhere in the prehistoric past. (We don't know how long ago.) These dwarfing genes appear to have originated with
Shiro Daruma, a semi-dwarf Japanese landrace wheat that has been around for millennia.
So, I'm afraid that
Rht-B1b was a naturally-occurring point mutation, as the article you quoted said—neither induced nor manipulated—which Japanese breeders exploited to create the Norin series of wheat through traditional Mendelian breeding, not mutagenesis protocols. See: Takeo Matsumoto, "Norin 10: A Dwarf Winter Wheat Variety,"
Japan Agricultural Research Quarterly 3, no. 4 (1968): 22–26.
For example, they crossed
Shiro Daruma (Japanese) with
Fultz (American) in the early 1900s to create
Fultz-Daruma, which was bred with
Turkey Red (Ukrainian) in the 1920s to create
Norin 10, which was registered in October of 1935. And it was
Norin 10 that agronomist Orville Vogel first introduced to America in 1946, crossing it with local wheat lines to create varieties like
Gaines. Norman Borlaug used
Norin 10 to create the high-yielding, semi-dwarf wheat varieties (e.g.,
Pitic 62) which fueled the Green Revolution in Mexico and beyond.
But this is just book-learning, so what do I know.
There are two ways to dwarf wheat: hybrid (controlled breeding), and Rht 1b which is an induced mutation, irradiated or chemical.
There is also a third way: A naturally-occurring mutation, found in Japanese semi-dwarf wheat.
Question: What is the source of your claim that the
Rht-B1b point mutation was induced?
Rht hybrids, if you buy a pack of F1 hybrid marigold, ...
I have a basic grasp of how hybrid seed crops work.
However, unlike F
1 hybrids (which segregate in F
2), dwarf wheat cultivars with these alleles are
homozygous,
pure-line, and
self-pollinating. These features explain why the dwarfing mutation is heritable, viable, and persistent across generations (contrary to your claim that mutations are sterile, not viable, and revert to type).
For the reader: The fact that these cultivars are homozygous across key loci is what tells us they're not F₁ hybrids.
A
homozygous locus (e.g.,
Rht-B1b/Rht-B1b) ensures that all progeny receive the same allele from each parent. In
pure-line wheat, virtually all key traits are genetically fixed, meaning the offspring inherit the same traits without variation. And
self-pollination ensures the integrity of the dwarfing trait is stably inherited.
By way of contrast, F
1 hybrids contain
heterozygous loci by design and, when replanted, the F
2 generation segregates phenotypically and genotypically, resulting in inconsistent performance. Dwarf wheat does not behave like this; it breeds true.
RhT 1b irradiation induced hybrids. Seeds require radiation and further contolled breeding to produce seeds with the mutation,
While there are Rht alleles created through radiation in wheat (e.g.,
Rht12 or other variants studied in mutagenesis programs),
these are not the alleles in Norin 10 or modern commercial dwarf wheat.
The dwarf wheat in the Green Revolution is a hybrid.
That statement is simply incorrect. The fact that these cultivars are homozygous is the genetic evidence that proves it.
F
1 hybrids, by definition, are (a) heterozygous at key loci, (b) genetically uniform in the F
1 generation but segregate in the F
2, and (c) not stable across generations (i.e., farmers can't save seed without performance loss).
Green Revolution dwarf wheat cultivars are (a) homozygous at key loci, (b) developed through traditional pedigree breeding, not hybrid seed systems, and (c) self-pollinating pure lines, so they breed true—no segregation, no reversion, no loss of dwarfing trait.
Hybrid dwarf wheat is not a mutation or evolution. ... So no, RhT 1b is not a mutation that can evolve
And we're back to saying it's not a mutation.
[Hybrid dwarf wheat] is created by breeding which has been practiced for thousands of years.
For the reader: She is not acknowledging the difference between traditional pedigree breeding (used in crops like dwarf wheat) and hybrid seed systems (used in crops like canola), perhaps failing to recognize their fundamental genetic and agronomic differences.
Traditional pedigree breeding is a method of line breeding that uses successive self-pollination and selection to produce
homozygous, stable, true-breeding cultivars.
Hybrid seed systems involve crossing two distinct homozygous inbred parental lines to create an F
1 hybrid that is
heterozygous and genetically unstable in subsequent generations—traits segregate in F
2, which is why farmers must purchase new seed each season.
RhT 1b irradiation induced hybrids. Seeds require radiation and further contolled breeding to produce seeds with the mutation,
However the mutation is subject to repair and deselection so, in the long run, not viable. The irradiated strains shed the mutation in subsequent generations...deselection and repair
New seeds have to irradiateed to keep the mutation in subsequent generations.
The dwarfing genes were not produced by artificial irradiation. It was found in a Japanese landrace wheat and subsequently used in pedigree breeding programs, not mutagenesis protocols.
(We are also back to saying it's a mutation again. My head is starting to spin.)
It helps to have hands on experience with animal and plant genetics, as book learning is just repeat-after-me.
I am content to let the reader be the judge of that.
I AM REITERATING MY REQUEST BECAUSE IT IS IMPORTANT:
Question: What is the source of your claim that the
Rht-B1b point mutation was induced?