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Is this another possibility

Posted by karyn1 MD 7 (bhkalen@aol.com) on
Thu, Jul 22, 10 at 8:12

I used caerulea pollen on a citrina bloom and a fruit has developed. Is this a possibility? It's outside so an insect could have pollinated it but that's never happened before.


Follow-Up Postings:

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RE: Is this another possibility

Hi Karyn,

Highly unlikely it pollinated it--they have a different number of chromosomes (2n = 12, citrina, 2n = 18, caerulea).

Perhaps it caused the citrina to self?


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RE: Is this another possibility

Thanks Randy. One day I'll have to read up on the genetics of passifloras and who can pollinate who and who's sterile or partially sterile. It's just so complicated and easier to come here and ask. lol There's some decalobas blooming in the greenhouse so maybe an insect was in there and then landed on the citrina outside or maybe trying to hand pollinate did cause it to self? At least it finally has a fruit and an odd looking one at that.


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RE: Is this another possibility

Hi Karyn,

Though Randy is correct about the chromosome count, I would not use that as my only indicator for whether on not a hybrid is possible. Stranger things have happened...

The main thing that tells me that it is extremely unlikely is how far removed they are from one another genetically. As far as I am aware, a Passiflora and Decaloba have not ever been successfully crossed. I have tried many myself, have a ripening fruit on one, and know another person with a fruit ripening also trying to break the "Pas-Dec divide". The parents I chose were done so for specific reasons which made me think they would have a higher chance of success. This is still very unlikely to yield a positive result.

Though P. caerulea is a potent pollen donor, I still think the chances of it being a cross are way less than 1%. Even if it DID work, and you have viable seeds of the hybrid, and it germinates, the likeliness is that the resulting offspring will be weak, never bloom, and probably not make it past seedling stage. There are many hybrids that this happens to just due to the fact that though the pollen and ovary were compatible, the genes just are not, and you get a bad plant. Some are chlorotic, some have extremely poor immune systems, and so on. I know all this not just from reading, but from plenty of experience. It is always rough to germinate a cross with massive potential of being cool, to just have it be that way. It's a bummer...

Sorry to be so negative about it, but at least you won't get your hopes too high. Keep trying, though!

Best wishes,
Eric Wortman


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RE: Is this another possibility

I appreciate the info. I figured that it was unlikely but wanted to confirm it. Since it's not too far from the greenhouse where I had some other decalobas in bloom maybe a bee or something could have visited both flowers. If the caerulea caused it to self is there a possibility that the fruit could yield viable seed? All I can do is wait and see what happens with the fruit.

Next question. My P. holosericea is blooming. Can I use citrina to pollinate it and visa versa? That's the only other decaloba that is open now.


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RE: Is this another possibility

  • Posted by pshawn 9B, California (My Page) on
    Fri, Jul 23, 10 at 13:47

I'll defer to Eric and others on the most recent questions since I haven't tried those particular crosses yet (P. holosericea X P. citrina and vice versa).

As far as the original (P. citrina X P. caerulea) question, I completely agree with Randy and Eric, and have an additional thought. One other explanation for what happened with your citrina is asexual fruiting. I don't happen to know if P citrina ever does this, but some passiflora do. For example, I have noticed what I believe to be asexual fruiting recently on my P. caerulea. Lots of small, empty fruits, no apparent pollen donor. Anyone know if P. citrina does this?

I also agree with Eric about the pass-dec divide. While it's is highly unlikely to cross, some of us are trying... with some hope that it may happen someday soon if we try (or have already tried) the right combination. I have fruit that have potentially crossed this divide too. Unlikely to pan out for all the reasons Eric stated, but we all still should cross our fingers for each others' attempts!!!


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RE: Is this another possibility

Shawn when you say asexual fruiting do you mean the same as selfing? The other (caerulea in this case) pollen not contributing any genetic material but triggering the fruit to develop.


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RE: Is this another possibility

I was going to ask whether Shawn meant parthenocarpy--fruit is formed, but no viable seeds.


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RE: Is this another possibility

  • Posted by pshawn 9B, California (My Page) on
    Fri, Jul 23, 10 at 21:32

Yes, basically reproduction without meiosis and genetic recombination of maternal and paternal chromosomes. Instead, mitotic reproduction only with maternal genes alone (i.e. no contribution from pollen at all). I'm no expert on this process in plants (and why it may not produce seeds), just a thought from a general biologist...


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RE: Is this another possibility

Okay, the person WITHOUT a PHD is going to chime in again...

Karyn, the P. holosericea and P. citrina are definitely closer relation than P. caerulea to either. Likely, still... no. But worth a try, for sure. We have found that the Xeragona section of Passifloras, (ie citrina, sanguinolenta, capsularis, quinquangularis), have never set fruit with anything outside of the section, though they set readily within. I am not familiar with any crossovers being made, but it is possible that they have just not tried with enough determination. Decalobas, in general, are not frequently hybridized. In my opinion, that is because they are not as commercially appealing to the masses.

We have never had holosericea flower for us, but we would definitely try it with any Decaloda we had open! Again... stranger things have happened. Isn't that right, Shawn?

Eric


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RE: Is this another possibility

Eric,

Speaking of Decalobas, and this is WAY, WAY off topic. Can one potentially dwarf a Decaloba by grafting it onto a different rootstock? I have a huge Decaloba (membranacea) and then a few tiny ones (Manta, sanguinolenta, Sunburst...).


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RE: Is this another possibility

  • Posted by pshawn 9B, California (My Page) on
    Sat, Jul 24, 10 at 2:02

Stranger things have happened than a xerogona crossing with another decaloba. I am trying with some determination right now a number of crosses with P. sanguinolenta, but NOTHING has worked yet.

To clarify my previous comment, there is a difference between selfing and asexual reproduction. Selfing, I believe, actually involves meiosis and recombination of chromosomes (though both sets of chromosomes from the same parent), whereas asexual reproduction involves only a replication of parental chromosomes in their current state. I wish I had a chalkboard or grease-board to draw out what I mean. As a practical example, P. edulis selfs and makes viable fruit. Meanwhile P. caerulea and others do not self, but will have asexual reproduction that produce empty fruits.

There are certainly people who read and contribute to this forum who have a much more nuanced understanding of this than I do--especially Eric, Randy, and those who have taught me bits about polyploidy. Any others of you reading this string and care to comment?


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RE: Is this another possibility

Shawn, I'm pretty sure you are describing parthenocarpy--fruit but no seeds.

Another phenomenon which can result in seeds that are genetically identical to the parents is apomixis. In that case there would be no meiosis.

If there has been self-pollination the seeds are not genetically identical to the parent.

I think someone has written nice articles on the first two terms for Wikipedia:

Parthenocarpy: http://en.wikipedia.org/wiki/Parthenocarpy

Apomixis: http://en.wikipedia.org/wiki/Apomixis

Here is a link that might be useful: Wikipedia article on Parthenocarpy (same as above)


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RE: Is this another possibility

  • Posted by pshawn 9B, California (My Page) on
    Sat, Jul 24, 10 at 13:45

Wow! Thanks Randy! I have learned a bunch about asexual reproduction in plants from this discussion (though let's be clear that "selfing" as we tend to use the term for passiflora is sexual reproduction even if within the same parent plant... right?).

Let me see if I've got it right about parthenocarpy and asexual reproduction in plants from my simplified perspective:

-parthenocarpy: fruit production with no seeds, but not asexual reproduction (may or may not involve pollination)

-apomixis: a blanket term including many different forms of asexual reproduction in plants--none of which include true meiosis and so offspring are the same genetically as parents (except maybe in chromosome number)--one example is a plant making seeds that have identical genetics to the parent plant, another would be flwoers replaced by bulbils to make a new, identical plant.

So, Karyn: I guess I should revise my comments to say your plant may have undergone parthenocarpy (stimulation from P. caerulea may have induce parthenocarpy in P. citrina). I used "asexual reproduction" incorrectly above because I'm fundamentally a human biologist not a plant one! Thanks Randy, for setting me straight!


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RE: Is this another possibility

  • Posted by pshawn 9B, California (My Page) on
    Sat, Jul 24, 10 at 17:19

Ugh. I'm going to stop correcting myself after this because I keep getting terminology wrong. Last thing, though: parthenocarpy may or may not involve pollen inducing the process (which is not pollination).


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RE: Is this another possibility

I've certainly learned something from these posts. I questioned if the caerulea could have induced selfing in the citrina in the original post so I guess that's a yes. lol

Speaking of parthenocarpy I assume that's what's happening with my caerulea. I get fruit that ends up just being a balloon, no pith (or not much) and no undeveloped seed. What's odd, or maybe not, is the caerulea fruits feel heavy and full early on but by the time they ripen they've become very light and when opened are empty. A caerulea fruit dropped off in my hand today and was empty as can be.


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RE: Is this another possibility

Shawn,

I'm not a plant biologist either--this is all new to me. I've mostly worked with bacteria.

I have wondered about the phenomenon by which exogenous pollen stimulates selfing and why this happens. Could it be that the advantages of producing seed by pollination with another clone become a luxury when the plant senses competition, that is, a different species in the area? So that the plant "decides" that it needs to produce seed, regardless? I've asked the question before and never gotten an answer.


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RE: Is this another possibility

Randy have you asked about that on the other passiflora board (passiflora 1 ?). I think it's more likely you'll get an answer there.


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