Opuntia genetics for no spines

[Glochid Fingers]

Hi.
I've been wondering what would happen if you crossed a spineless (glochidless too) opuntia with a normal one of a different species. Is it inherited? Or is spineless a physical mutation(like a crest)? Any information would be helpful.
Thanks.

[CactusFanDan]

You'd be more likely to get spineless offspring than you would by crossing two normal plants. On average though, the offspring would be spinier than the spineless form (obviously). It's more of a numbers game, I'd say. The more seed you get and sow, the more likely you are to get spineless plants coming up. Also, a funny thing with Opuntiads is that they produce less glochids when grown in stronger light. Spineless varieties may only be spineless if grown in full sun, whereas a pad from the same plant grown in shade will produce lots of glochids. That's something I've observed in my greenhouse.

[A. Dean Stock]

Hybrids with a generally spineless species like Opuntia basilaris and a spine bearing species, always have spines in the primary hybrids. Most crosses I've seen with spineless or generally spineless forms like O. aurea have spines like the parent with spines. As an example, hybrids with O. aurea x O. macrorhiza have long spines but only on the terminal 1/4 of the pad. Hybrids with O. aurea or O. basilaris with O. erinacea have spines along the length of the pad.
I find just the opposite with light; stronger light produces more spines not less. Of course, what you call strong light in England would pass for a very cloudy day here. Many species with spines such as Opuntia pinkavae with strong spines develop more ( and longer) spines in years with higher rainfall than average so spine development depends on genetics, light and availabilty of water (at a minimum).
Dean

[CactusFanDan]

Hybrids with a generally spineless species like Opuntia basilaris and a spine bearing species, always have spines in the primary hybrids. Most crosses I've seen with spineless or generally spineless forms like O. aurea have spines like the parent with spines. As an example, hybrids with O. aurea x O. macrorhiza have long spines but only on the terminal 1/4 of the pad. Hybrids with O. aurea or O. basilaris with O. erinacea have spines along the length of the pad.
I find just the opposite with light; stronger light produces more spines not less. Of course, what you call strong light in England would pass for a very cloudy day here. Many species with spines such as Opuntia pinkavae with strong spines develop more ( and longer) spines in years with higher rainfall than average so spine development depends on genetics, light and availabilty of water (at a minimum).
Dean

Perhaps it's a different situation for what I'm thinking of, since I'm thinking of O. fragilis v. denudata (debreczyi?) ,which is what I have. It only develops spineless and glochidless pads on the top shelf of the greenhouse, whereas cuttings grown in the shade under the shelves develop strong glochids. The same applies to Pereskiopsis - they develop more glochids grown indoors than in the greenhouse.

Notice the use of the word glochids as opposed to spines as well. Also, the full sun I was referring to would be full sun in the height of Summer with no cloud cover. Light intensity would not be that different in your neck of the woods in the height of Summer with no cloud cover (see Fig 6 here:http://www.ccfg.org.uk/conferences/down ... urgess.pdf). Anyway, those conditions are what made the aforementioned Opuntia produce totally naked pads. Interesting effect.

[A. Dean Stock]

Dan, come on over here during July some time and I'll show you the difference in light intensity (including spectral differences) compared to England. I haven't spent much time in the "land of mists" but the lack of humidity and air pollution in the U.S. southwest deserts means that it gets a lot brighter ( and hotter).
The Opuntia fragilis plants with few or no spines ( often referred to as "denuda") are often hybrids and may show very different growth and spine formation at different light and humidity levels. Note that "denuda" and "debreczyi" are not accepted names for any population of O. fragilis. Glochids are coded by different genes than spines and often develop more in lower light while spines do not. The most glochids I've ever seen have been on underground stems of various species, especially in sandy areas.

Dean

[Glochid Fingers]

Wow. You guys both talked about the two plants I'm interested in. O. basalaris and o. Fragilis denuda. Would there be any hybridization issues with these two plants? I have basalaris but am looking for the denuda. Also need to store some pollen as I imagine they won't flower simultaneously.

[CactusFanDan]

Dan, come on over here during July some time and I'll show you the difference in light intensity (including spectral differences) compared to England. I haven't spent much time in the "land of mists" but the lack of humidity and air pollution in the U.S. southwest deserts means that it gets a lot brighter ( and hotter).
The Opuntia fragilis plants with few or no spines ( often referred to as "denuda") are often hybrids and may show very different growth and spine formation at different light and humidity levels. Note that "denuda" and "debreczyi" are not accepted names for any population of O. fragilis. Glochids are coded by different genes than spines and often develop more in lower light while spines do not. The most glochids I've ever seen have been on underground stems of various species, especially in sandy areas.

Dean

Was that an invitation? I'd love to come visit! I didn't know about the different genetics of glochids and spines either, so thank you for that.

Wow. You guys both talked about the two plants I'm interested in. O. basalaris and o. Fragilis denuda. Would there be any hybridization issues with these two plants? I have basalaris but am looking for the denuda. Also need to store some pollen as I imagine they won't flower simultaneously.

They might flower at similar times. If you do end up getting both and they flower at the same time there's no harm in trying to cross-pollinate.

[A. Dean Stock]

Dan, if you ever "cross the pond" I'd be happy to show you around the southern Utah/northern Arizona deserts.
O. fragilis x O. basilaris makes a nice tetraploid hybrid which is fertile. Hard to make the cross though because O. fragilis "denuda" seldom flowers for me.
Dean

[Glochid Fingers]

Very helpfull guys!
Dean, thank you for verifying that they are compatable. As for flowering the fragilis I will just have to do my best and have a bit of luck.
I also am looking for that very plant in the plant swap forum, you can't miss it;)

[jorgeq]

Interesting talk about glochidless cacti. I don't have any of the nearly glochidless/spineless forms of O. fragilis (thinking the well-known O. debreczyi var. denudata {Potato Cactus}). Its on my want list, however.

I do have what is probably the only North American truly glochidless AND spineless Opuntia (O. microdasys cv. ‘Caress’) that I imported from Europe. Its supposedly originated in a European nursery. Its a eunuch version of an Opuntia: you can rub it on your face with no damage done since it has no glochids.