Apomixis in Orchids

[orchidsarefun]

I heard today from the lab that seedlings of the first pod are "growing very strangely". I will take a photo when I visit tomorrow. This would however indicate that the first pod, at least, wasn't apomictic.........or maybe not , according to your explanation. Or maybe 50/50, with the 2nd 50% being the genetically "impossible" cross ? Growing strangely would support this view, but I wonder why the seeds germinated if the genetics/ploidy wasn't kosher.......
It's a fascinating subject, with an answer only when these seedlings themselves bloom - if they ever get to that stage.

[GluttonousSolarWrasse]

Interesting-I'd love to see the photos. In theory, with an obligate apomict you'd expect a very high number of the offspring to resemble the parent exactly, with maybe a few plants the results of an out cross. That is literally the test for apomixis as I understand it. In other words I'd perform a cross on a know apomict, a citrus species for instance. I'd grow out the seeds from that fruit, and the oddball looking offspring would be considered the results of sexual fertilization, while the clonals would be the results of apomixis. however, you CAN have a spectrum of apomixisi or likelyhood of apomixis in and apomictic plant, those wouldn't be considered obligate apomicts is all.

Now growing strangely-in theory if the pollen parent had an odd number ploidy, like 5n or 3n etc. the pollen would be sterile. it couldn't possibly go through meiosis properly. The pollen could physically develop, but would be useless, meaning the cross would not take at all I would think. Now if the pod parent was a 4n, and the pollen parent was like a 6n, or something, the gametes on both side would be viable, and result in a 3n pollen and a 2n ovum. THese would fuse to form a 5n. Now that plant, while in the future would be sterile, should not have its mitotic division into a fully developed plant hindered much-if at all. Most plants are extremely tolerant of odd ball ploidy conditions like that. In other words, I don't think you'd notice a difference in their development now. What you may have is two ALMOST chromosomally compatible plants, and an unlikely cross that took. the resulting dividing cells could have problems lining up the chromosomes during mitosis, since maybe allele the loci don't match, the chromosome sizes don't match, the number of actual chromosomes was wrong (like an extra or two in there maybe?) like crossing a 2n=2x=24 with a 2n=2x=26.

Or maybe orchid apomicts develop in a slightly weird fashion early on?

[Fairorchids]

Originally Posted by orchidsarefun

Actually it was a well known breeder who runs a specialised orchid forum who alerted me to the possibility, but couldn't provide specifics. I just want to know if anyone else can provide pertinent input on this issue.

Does anyone have a link to scientific study showing that this condition is possible in Orchids?
At this point I consider this issue to be hearsay and guesses.

[orchidsarefun]

Originally Posted by Fairorchids

Does anyone have a link to scientific study showing that this condition is possible in Orchids?
At this point I consider this issue to be hearsay and guesses.

ever heard of Google Scholar ? Use it in future ? I got these results in less time than it took for you to post your comment

apomixis in orchids - Google Scholar

---------- Post added at 10:42 AM ---------- Previous post was at 10:09 AM ----------

http://culturesheet.org/_media/users...33.pdf#page=47

found this comment by chance:

the specialists describe two forms of apomixis: agamospermy, in which reproduction takes place by seeds formed "without fertilization" - or vegetative
apogamy in which reproduction is by cells of the mother plant other than the egg cells. These phenomena are well known in certain families such as Amaryllidaceae,
Cactaceae ,Poaceae , etc. It has also been reported in some orchid genera such as Rabenana , Orchis , Malaxis , Spiranthes , and Zygopetalum , to which I like to add some scandent species in Oncidium and a unique case in Laelia urata , in my own collection.
( my bolding )

so - if I take this comment at face value ( ie without requiring 10 different scientific studies ), then it is possible for my orchid to be apomictic as it has a zygopetalum parent !!!

Photo of 1 flask with "strange growth" of seedlings.

[GluttonousSolarWrasse]

Well that certainly ups the odds that you might have an apomict there. (which is super cool) In a lot of my classes we looked at apomixis as kind of a holy grail solution to great reproduceable seed stock that always had consistent progeny. Imagine the applications-hybrid corn, where one inbred line parent is the apomict. make the cross, and you progeny get all the benefits of heterosis, the consistency of hybrid seed from two inbred lines, AND the apomictic state. You have a corn with all the benefits of hybrid corn, and now reproduced asexually through apomixis-it's literally perfection to a plant breeder. It is essentially a way to breed in what traits you want, using any method you want, then locking in that cultivar's genetics to have it reproduce perfect copies asexually. That is why apomixis is so cool. However, I think it is on the rare side for the most part. Also breeding with apomicts can also be a huge pain in the butt when you can't get any outcrosses. This is a super cool thread, please keep it updated!

[orchidsarefun]

it is interesting that amaryllicae are mentioned too because I selfed an "exotic" type amaryllis and grew the seeds on. I had read various anecdotal articles that it was unlikely that these types breed "true" from a selfing. I gave some seedlings to my folks in South Africa last year and last week I was shown the first blooms. They are EXACTLY the same as the parent ! I have about 50-100 ( !!! LOL ) bulbs stored in my basement - I am too scared to look to see if they are still OK - but hopefully I can get a couple to bloom this year too. I am not saying that mine is apomictic at all, but its interesting connecting the dots. I have an amaryllis seedling thread on OB.

As for my zygonisia cross, the propagator is going to move all to a different media to see if that helps.

[GluttonousSolarWrasse]

That is too cool! I love amyrillis as well, I did not know that some are potential apomicts. It seems like you are running into apomicts all the time! I think overall apomixis in orchids would be pretty rare. Maybe confined to a genera or two. I say that anecdotally though, my theory is based upon the lengths orchids go to to attract pollinators, avoid self pollination, I.E. anything to encourage out-crossing.

[OCRC_Dir_China]

A good article from the NORTH AMERICAN NATIVE
ORCHID JOURNAL Volume 3
Number 3 September 1997
I like how the writer kept the explanation of apomixes simple.

APOMIXIS IN ORCHIDS?
Mariano Ospina H.
In the September, 1995 issue of the North
American Native Orchid Journal, Paul Martin Brown
reports the rediscovery of Dactylorhiza aristata
(Fisch.) Catling forma perbracteata Lepage, in a brief
passage: "Mariano Ospina spotted the flowerless
individual at the edge of a small bog as we were
leaving an area near the Fossil Cliffs on Kodiak
Island" - of course in Alaska (Brown 1995). This
strange plant had been reported only once, by its
discoverer, Ernest Lepage, in the American Midland
Naturalist 46:757, 1952, and the next thing to do
would be to find the type specimen which had been
deposited in the Langlois Herbarium, Catholic
University of America (LCU). Unfortunately, said
herbarium had been dispersed ca. 1986, as reported by Arthur 0. Tucker et al. in Taxon, and most of the
collections were "sold by families..." in which the
Orchidaceae appeared as sent to WIS, the herbarium
of University of Wisconsin, at Madison (Tucker
1986).
On the basis of said information, the search was
directed to WIS, but the brief reply received from
the Collections Manager said simply: "Orchis aristata
forma perbracteata Lepage 25014, not in WIS ... try
the National Arboretum (NA) which got the separate
type collections from LCU." After an interesting
exchange of notes with NA, I finally obtained the type specimen Lepage No. 25,014, June 16, 1949, with the note: Floribus nullis; bracteis numerosis (40-50) valde elongates. Kodiak Island, Isthmus Point,
grassland on low sea-cliff."
The next step was to check the map of Kodiak
Island in order to pinpoint the two locations on which
this strange orchid had been found so far. A look at
said map (2) shows that the two locations, Isthmus
Point and Fossil Cliffs (near Pyramid Mt.) are some 50
km apart and, consequently, the next question was,
how can a "Floribus nullis" orchid species or form
survive for nearly 50 years with a range of some 50
km?
The textbook answer to this riddle seems easy.
According to H. Winkler, all plants and animals can
be ranged within three groups so far as their mode of
reproduction is concerned (Richards 1986). These
organisms in which sexual differentiation and
fertilization have not yet arisen are called amictic.
The sexually differentiated organisms are called
mictic, and among these we find some of them can
reproduce without fertilization and are named
apomictic. Thus, apomixis is "a derived stage in
which the fertilizing mechanism once acquired has
been lost again. Furthermore, the specialists describe
two forms of apomixis: agamospermy, in which
reproduction takes place by seeds formed "without
fertilization" - or vegetative apogamy in which
reproduction is by cells of the mother plant other than the egg cells. These phenomena are well known in certain families such as Amaryllidaceae, Cactaceae, Poaceae, etc. It has also been reported in some orchid genera such as Rabenana, Orchis, Malaxis, Spiranthes, and Zygopetalum, to which I like to add some scandent species in Oncidium and a unique case in Laelia urata, in my own collection.
Finally, we may ask, is there any "practical"
implications for this line of research? Probably, yes.
At least if we pay attention to the conclusions
presented by Ellen T. Bauder in a paper entitled
"Genetic Diversity: Esoteric or Essential", where she
says: "Diversity protection on the local or micro scale
may be essential to the longevity of a species, but this effort could leave some unprotected species. These unprotected species fall primarily into two groups: habitat specialists, such as in disturbance regimes, edaphic conditions, ephemeral wetlands, and plants with reproductive systems that are asexual ... Plants that fit into either or both of these categories warrant a close examination of their genetic diversity." (Bauder 1993). I believe that Dactylorhiza aristata forma perbracteata deserves such further examination.
References:
Bauder, E.T. 1993. "Genetic Diversity- Esoteric or Essential"
Proceedings Symposium on Interface Between Ecology and Development, Southern California Academy of Sciences, Los Angeles. p. 39
Brown, P.M.1995. Some interesting nomenclatural and
distribution notes on Alaska. North American Native Orchid Journal 1(3): 242.
Richards, A. J. 1986. Plant Breeding Systems, Unwin Hyinan, London. p.7
Tucker, A.0., Poston, M.E., Ilitis, H.R. 1986.
History of the LCU Herbarium, 1895-1986. Taxon, 38(2): 196-203.
Mariano Ospina H., 42 Fernald Dr., #11, Cambridge, MA
02138. Mariano is a Harvard Research Associate with The
Orchid Herbarium of Oakes Ames at the Harvard University
Herbaria. His most current publication is a new book - To The
Rescue of Paradise - Orchids in Columbia.

[orchidsarefun]

yes - and the other parent of zygonisia is Aganisia/Acacallis, found in

Brazil, Colombia, and Venezuela. These epiphytic plants are found throughout the upper Amazon Basin, particularly above the confluence of the Amazon and the Río Negro, and along the upper Río Orinoco above Puerto Ayacucho in western Venezuela. Plants grow in the flat, low-lying forests in areas that are completely innundated during seasonal floods. Visitors to the habitat have reported seeing host trees partly underwater during a flood with the Acacallis cyanea mostly under water except for part of the rhizome, 1 or 2 of its leaves, and the inflorescence. -- Source: Charles Baker

and this habitat ties in with this comment from the article - Ellen T. Bauder

"Diversity protection on the local or micro scale
may be essential to the longevity of a species, but this effort could leave some unprotected species. These unprotected species fall primarily into two groups: habitat specialists, such as in disturbance regimes, edaphic conditions, ephemeral wetlands, and plants with reproductive systems that are asexual ... Plants that fit into either or both of these categories warrant a close examination of their genetic diversity." (Bauder 1993)

Zygopetalum........and possibly Aganisia ( because of growing in ephemeral wetlands ) are candidates for apomixis and a logical conclusion is - so is the cross between the two !!!

---------- Post added at 09:08 PM ---------- Previous post was at 08:55 PM ----------

Originally Posted by GluttonousSolarWrasse

I think overall apomixis in orchids would be pretty rare. Maybe confined to a genera or two. I say that anecdotally though, my theory is based upon the lengths orchids go to to attract pollinators, avoid self pollination, I.E. anything to encourage out-crossing.

I agree - and its puzzling with zygopetalum as the blooms are highly fragrant, showy, sizeable...and at least 5 on each spike. Actually aganisia/acacallis also has showy blooms with at least 3 ( 4.8cm spread ) blooms, though they are not scented. I don't know if flower colour is a negative impact on natural pollination as aganisia have mostly blue/white flowers.

[Fairorchids]

I have followed the links and read the material that I get to.

There is mention of this condition, but no scientific proof is documented.
Zygos are not known for producing spontaneous seed pods.
I have seen enough variation in Zygo hybrids (and in particular in intergeneric Zygo hybrids), that I maintain that this is more speculation than documented fact at this time.

I am willing to explore this further. Does anyone have a copy of the A.J.Richards book, that I might borrow?