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Some oxeye daisies (Leucanthemum vulgare) in my garden are showing strange mutations. I have a few oxeye daisy plants around my garden in different areas, but only one plant's flowers are showing these mutations. When I search 'oxeye daisy mutation' on Google, this specific mutation does not appear. I will attach three pictures to show this on three different flowers, but there appears to be a new flower growing out of the yellow middle of the daisy. Was this caused by a genetic mutation? Maybe an infection?

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This is a known phenotype, including among asters (see also here), known as "doubling" or "double flowering". In the model plant Arabidopsis thaliana, it is well described as a homeotic transformation related to a genetic mutation:

The first documented double-flowered mutant of Arabidopsis, a model organism for plant development and genetics, was recorded in 1873. The mutated gene likely responsible for the phenotype, AGAMOUS, was cloned and characterized in 1990 in Elliot Meyerowitz's lab as part of his study of molecular mechanisms of pattern formation in flowers. [link to Meyerowitz paper]

One paper in a Ranunculus has a very nice figure reproducing the AGAMOUS connection in a doubled ornamental cultivar: ranunculus showing agamous mutant and silencing doubled phenotypes

Other work in such species as primrose does show the kind of variable penetrance for sepal-->petal conversions ("Hose-in-hose" phenotype) such as we see here for a homeotic mutation (called "revertant"/"semi-revertant"):

variable penetrance of homeotic conversion

The cause of this variable penetrance appears to be transposon hopping out in the mutant. Unclear whether that could also be true in your case.

The fact that multiple flowers from the same root stock show the same phenotype argues that it is common to the plant, and not just a stochastic event. What actually causes it would take some molecular work to prove, but given the repeated emergence of this heritable phenotype across many different kinds of flowers across centuries, genetic mutation is certainly the leading explanation from available data.

Granted, genetic mutation is not the only cause of this kind of homeotic transformation. At the end of the day, these kinds of mutations are the result of ectopic expression of a gene- and that ectopic expression is, as pointed out in other answers, not necessarily heritable or genetic. This may include viral expression, or even insect galls.

I'd suggest that you could narrow it down to heritable or non heritable by collecting seeds from your plant and sowing them in various locations, and seeing if you get stable inheritance across locations (or stable proportions of inheritance).

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  • $\begingroup$ Collecting seeds is a great suggestion, and might be the best way to determine the cause of this "abnormal" expression. One question (may not have an answer): why aren't all the flowers affected similarly? (Some have more ray flower expression than others, and some are normal.) Asteraceae and Rosaceae have the highest aphid burdens (of flowering plants) and the viruses they carry spread like they do, kind of contiguously. The plasticity of expression seems to me to be consistent with a virus, but I truly don't know. Purely guessing here. $\endgroup$ Commented 2 days ago
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    $\begingroup$ @anongoodnurse thanks for comment- I added some more examples, including one example of a floral homeotic mutation with variable penetrance driven by transposition. Interesting topic! There seem to be a lot of possible mechanisms. $\endgroup$ Commented yesterday
  • $\begingroup$ It is interesting! Lots of research on commercial plants but not so much on ornamentals. Very nice answer. The primrose info is very supportive. $\endgroup$ Commented yesterday
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Keep in mind that not all unusual forms come from mutations. In addition to the previous answer that MadaboutMonarchs suggested, it may be just a developmental glitch, maybe due to insect damage or other injury (unless it appears on more than one flower,... then likely genetic).

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    $\begingroup$ Re the parenthetical at the end of the answer, the original question states that the unusual flower form appears on multiple flowers (of a single plant). $\endgroup$
    – mgkrebbs
    Commented Jun 9 at 23:18
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It's likely not a mutation, but rather a change in gene expression. Other asterids (like Chrysanthemums) like your daisies, have two different types of florets, rays and discs. The rays are the white florets and the yellow are the discs. Environmental factors can effect whether a floret expresses as a disc or ray, even if it typically expresses as the other.

https://link.springer.com/article/10.1186/s12864-016-2733-z

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    $\begingroup$ Your reference notes difference in expression between the tissues, but it does not seem to support a model in which only gene expression would lead to the observed homeotic transformation. Do you have other evidence for such a regulatory change underlying a homeotic transformation/morphological change in the floral body plan? $\endgroup$ Commented Jun 6 at 17:50
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    $\begingroup$ Hi and welcome (apologies if this comment seems unwelcoming.) On any science site, being able to interpret the literature you use as a source accurately is paramount. The source you cited does discuss differences in expression of appropriate disc flower and ray flower tissue, but states nothing about abnormal expression. As @MaximilianPress asked, please back up your answer about abnormal expression with a better source. Thanks. ... $\endgroup$ Commented Jun 7 at 11:48
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    $\begingroup$ ...Clearly it's about a change in expression (there's no other way to get such an anomaly), but what caused this change? A virus/bacteria/fungus/injury/mutation/other? $\endgroup$ Commented Jun 7 at 11:52

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