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Author Topic: Cherimoya/Pawpaw hybrid  (Read 12497 times)

usirius

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Re: Cherimoya/Pawpaw hybrid
« Reply #75 on: August 18, 2019, 09:04:29 AM »
@All:
Thanks for sharing your opinions and thank you for your realistic assessments, advice and encouraging words. So I will observe the plants for a while and maybe this year I will also create a pure Cherimoya pollinated Cherimoyaflower to get real Cherimoya seeldings from my mother plant as base for comparison - this will happen earliest next year of course, so long I will keep on watching the current seedlings and creating new pollinations on the few remaining Cherimoya flowers of my Cherimoya plant. Sorryly most of the Asimina-pollinated Cherimoya flowers dried within two or three weeks. With Asimina pollinated Cherimoya flowers stay more longer alive than time unpollinated Cherimoya flowers is until they dry out - but most of Asimina-pollinated Cherimoya flowers die within two to three weeks. But a few are stiill alive and I hope that they will remain alive and no insect has helped me by doing pollination...
I will keep you informed.
„May your choices reflect your hopes, not your fears.“ N. Mandela

Radoslav

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Re: Cherimoya/Pawpaw hybrid
« Reply #76 on: August 20, 2019, 10:19:59 AM »
I am not a specialist, but if the situation is similar to crossing diploids with tetraploids in citrus breeding, then it will be impossible to save embryo without separation and rising in vitro.

usirius

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Re: Cherimoya/Pawpaw hybrid
« Reply #77 on: August 21, 2019, 10:20:58 AM »
@Radislav: Thanks for your post. I think, and certainly most of the members of the forum who deal with hybridization, that it's as you write. By the way, we discussed this topic here in this section some time ago. Nevertheless, it cannot be excluded that pollination is successful even with different chromosome numbers of cross partners, because it can also be assumed that degenerated or modified cells or Cell information can be contained, further can by tricks such as the use of gibberlic acid (which I have not yet tried, I will still try next year), further also post-pollination with own pollen, inverse hybridization, hybridization of one among themselves incompatible individuals (I have such an Asimina) with Annona, and certainly still further possibilities then nevertheless a hybrid can develop, to what extent this forms a complete germinable seed, and to what extent this forms again a viable plant, is the question. Perhaps one would have to try to hybridize plants of the Annona family with more closely related Annonas (Atemoya) via a detour of hybrids. I think that, despite scientific evidence and experience, surprises might be possible.We will see.
„May your choices reflect your hopes, not your fears.“ N. Mandela

Guanabanus

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Re: Cherimoya/Pawpaw hybrid
« Reply #78 on: August 21, 2019, 08:48:38 PM »
Another technique, not mentioned above, is pre-germinating pollen before applying it to the pistil.  But I have no knowledge of how to do that.
Har

usirius

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Re: Cherimoya/Pawpaw hybrid
« Reply #79 on: August 22, 2019, 04:09:16 PM »
 Thank you for sharing the hint to another interesting sounding  method - I will do a research concerning  this. In case if success I let you know if course.
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usirius

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Re: Cherimoya/Pawpaw hybrid
« Reply #80 on: August 24, 2019, 02:58:08 AM »
Concerning pretreatment of pollen I found interesting literature. Handicap is in vitro culture but with this method one would have much more possibilities as can be read here - just two articles as for example:

https://www.intechopen.com/books/pollination-in-plants/pollen-germination-in-vitro

Pollen Germination in vitro

By Jayaprakash P
Submitted: November 20th 2017Reviewed: February 13th 2018Published: June 6th 2018
DOI: 10.5772/intechopen.75360

Abstract

Pollen germination in vitro is a reliable method to test the pollen viability. It also addresses many basic questions in sexual reproduction and particularly useful in wide hybridization. Many pollen germination medium ranging from simple sugars to complex one having vitamins, growth regulators, etc. in addition to various minerals have been standardized to germinate pollen artificially. The different media, successful pollen germination methods, procedures from pollen germination studies with wheat, rye, brinjal, pigeonpea and its wild relatives are discussed.



http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1677-04202002000100009

Pollen treatment in high osmotic potential: a simple tool for in vitro preservation and manipulation of viability in gametophytic populations

By: Leandro Lopes Loguercio 
Departamento de Ciências Biológicas - DCB, Universidade Estadual de Santa Cruz, Rod. Ilhéus-Itabuna, Km 16, Ilhéus, BA, 45650-000, Brasil; E-mail: leandro@uesc.br

Brazilian Journal of Plant Physiology
On-line version ISSN 1677-9452
Braz. J. Plant Physiol. vol.14 no.1 Londrina Jan./April 2002
http://dx.doi.org/10.1590/S1677-04202002000100009 

Abstract

A method for in vitro preservation and manipulation of pollen viability based on simple changes in osmotic potential (sucrose concentrations) in culture media was developed using tobacco pollen as the experimental model. High osmotic potentials were capable of reversibly inhibiting pollen germination, preserving its viability at room temperature for long periods, as assessed by subsequent incubation in germination medium. When pollen was pre-germinated for different periods and subsequently incubated in 80 % sucrose medium (inhibiting medium) there was a progressive decrease in its viability, which was a trend best described by a quadratic regression line. Nevertheless, very small variations in pollen-tube lengths and viable pollen grains more resistant to the pre-germination step were detected by this procedure. Consequences and potential applications of these findings were discussed for use in analyses of variability, selection in gametophytic populations and pollen storage.

« Last Edit: August 24, 2019, 02:59:41 AM by usirius »
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usirius

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Re: Cherimoya/Pawpaw hybrid
« Reply #81 on: August 30, 2019, 02:37:46 PM »
Interim report on my pollination attempts of Cherimoya flowers with Asimina pollen this year: After varying many different parameters, I came to the conclusion that it is possible to obtain fruit by pollinating cherimoya flowers with Asimina pollen. To what extent these fruits contain germinable seeds, and if the seedlings are actual hybrids or nucellar species, remains to be seen. Here are some photos:

1) These following two pictures show fruits, which were probably pollinated by others. Here I did not protect the flowers from pollination by insects. So insects may have pollinated those flowers succesfull with Cherimoya pollen:






2) These follwing three pictures show dried fruit preparations in which pollination definitely did not work.







3) These following two pictures Show two fruit sets where pollination worked and which are now obviously developing. Those flowers have definitvely got only Asimina pollen and no Cherimoya pollen!





« Last Edit: August 30, 2019, 02:41:51 PM by usirius »
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usirius

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Re: Cherimoya/Pawpaw hybrid
« Reply #82 on: September 07, 2019, 04:25:37 AM »
After about 30 different pollination tests I did this season on a grafted Cherimoya tree with several variation of various parameters, I have come to the conclusion that pollination of Cherimoya flowers with Asimina pollen is quite possible under certain conditions. Now I start a second series of tests on a Cherimoya seedling that is flowering for the first time.  At the moment it has one flower open, there is no other Cherimoya flowering in the area - at least in a radius of 10 kilometres. So this time pollination by insects with Cherimoya pollen is definitely impossible.  Now I have carried out the pollination exactly with the same procedure with same parameters and criteria, which according to my knowledge lead to success - i.e. to the formation of a fruit. I will report to you whether the fruit batch is developing.




« Last Edit: September 07, 2019, 04:28:06 AM by usirius »
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Guanabanus

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Re: Cherimoya/Pawpaw hybrid
« Reply #83 on: September 07, 2019, 08:45:28 AM »
One can close a flower with a small rubber grafting strip, or a rubber band, before and after hand-pollination, to exclude pollinators.

This can also retain higher humidity inside the flower's chamber, thus extending the viability of the pollen that you place there.

On the down-side, it is theoretically possible that this higher humidity and darkness would keep the stigmas receptive, until the flower's own pollen is released, so you might want to remove the band a few hours before male stage.
Har

usirius

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Re: Cherimoya/Pawpaw hybrid
« Reply #84 on: September 08, 2019, 04:09:57 PM »
Hi Guanabanus, sounds interesting, and Logical! Perhaps in the course of evolution Chermioya has developed from a formerly open flower to a flower closed during pollination in order to protect the pistils from dehydration and to keep the pollen as viable as possible and to optimise the pollination process. The additional closing by means of rubber band or adhesive tape could actually successfully prevent foreign pollination by insects, but depending on the humidity in the air and the temperature, it would also be possible for the pollen to form a cloud, possibly of your own pollen, if the flower changes into the male phase and you open it again too late. It would be worth a try in the next season in any case - I would consider this approach and try if this year's successful looking hybridized flowers would not have produced real hybrids at a later point in time.What I have also noticed, by the way, and what speaks a little to the assumption about you regarding the humidity in the flower, is that the pollination success also seems to depend on the weather conditions, i.e. whether it rains, whether the sun shines, whether it is cooler, whether it is hot, etc. This actually seems to have an influence on the success of pollination.
„May your choices reflect your hopes, not your fears.“ N. Mandela

CherimoyaDude

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Re: Cherimoya/Pawpaw hybrid
« Reply #85 on: August 29, 2020, 12:47:06 AM »
Diploid Asimina/Anona hybrids that Usirius is trying to produce will most probably be non fertile since two parents have different chromosome numbers.
But crossing the combination of two tetraploids will give a tetraploid hybrid with balanced chromosome number. This could be done either by a generation of tetraploid Asimina and Anona by colchicine  or oryzalin treatment and than crossing such plants, or by pollination of hybrid  atemoyas with an excess of Asimina pollen.

Triloba Tracker,
I do not think that triploid asimina will be very fertile like triploid citrus varieties.

How do tetraploid hybrids work if the have a different number of chromosome?

usirius

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Re: Cherimoya/Pawpaw hybrid
« Reply #86 on: August 29, 2020, 07:18:44 PM »
It is very interesting that hybridization in nature also works differently, as known from Mendel's law. Partly there are demarcations and formation of new species after hybridizations. It is amazing that many of our cultivars were made possible by hybridization of species with different sets of chromosomes, and this was possible 1000's of years ago without genetic engineering! How does that work? Quite simply, in meiotic mating, plants have the possibility to double the DNA without cell division by endomitosis, making the cell tetraploid. If the number of chromosomes doubles to (allo)tetraploidy by mitotic nondisjunction (endomitosis), the hybrids can make normal reduction division, because for each chromosome there is a homologous partner with which it can mate during meiosis.

(source: https://www.kunz.hhu.de/fileadmin/redaktion/Fakultaeten/Mathematisch-Naturwissenschaftliche_Fakultaet/Biologie/Institute/weitere_und_ehemalige_Dozenten/Prof._Dr._Kunz/07_Haldane_hybridogene_Artbildung.ppt)
 
Of course this effect can be provoked by various methods, as described in previous posts. But my hope is that it works without supporting measures, and I have received fruit attachments that definitely did not come from pollination with its own pollen. Now it is time to attract seedlings from the seed and to evaluate them.



« Last Edit: August 29, 2020, 07:46:12 PM by usirius »
„May your choices reflect your hopes, not your fears.“ N. Mandela

usirius

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Re: Cherimoya/Pawpaw hybrid
« Reply #87 on: September 02, 2020, 02:41:49 PM »
Concerning my hybridization trial I am now sharing some actual pictures:

- Original mother plant Annona cherimola without pronounced leaf tip








- Original father plant Asimina triloba with pronounced leaf tip







- hybrid (?) seedlings with pronounced leaf tip



It is not yet a proof, but it is an interesting feature, and of course it is up to the individual to form an opinion about whether the hybridization has worked. I will raise a part of the seedlings until flowering, and I have also produced other hybrid fruits on both parents, which are now ripening and whose seeds will be sown next year.  I am confident that I have achieved a breakthrough here.


„May your choices reflect your hopes, not your fears.“ N. Mandela

Guanabanus

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Re: Cherimoya/Pawpaw hybrid
« Reply #88 on: September 02, 2020, 05:06:55 PM »
Thank you for the update.  The plant shown is in beautiful health.
Har

usirius

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Re: Cherimoya/Pawpaw hybrid
« Reply #89 on: September 03, 2020, 02:45:49 PM »
Thank you Guanabanus for your feedback.

Now as you mention this  I have realized that the seedlings which have sprout in June/July are growing extremely vigorously, even though they are crammed together in a relatively small flower pot with not very valuable soil, and that they are twelve in one, maybe the vigor is another sign that the seedlings are hybrids? Because hybrids often grow stronger than their parents. And a double set of chromosomes would also lead to stronger growth, which could also explain the extremely large leaves for these young plants, which are also full sunny - just like the cherimoya mother plant, which has much smaller leaves :-)
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Guanabanus

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Re: Cherimoya/Pawpaw hybrid
« Reply #90 on: September 04, 2020, 04:43:39 AM »
Maybe.

But it is also normal for juveniles to have much larger leaves than the adult plants do.
Har

usirius

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Re: Cherimoya/Pawpaw hybrid
« Reply #91 on: September 04, 2020, 04:48:05 AM »
Yes, that may well be, although I have had cherimoya seedlings with much smaller leaves. You have to know that we had a lot of heat and sun this year, and the seedlings were always in full sun. Due to the circumstances, they should have made rather small leaves, but they didn't! I will of course continue to observe what happens.
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Triloba Tracker

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Re: Cherimoya/Pawpaw hybrid
« Reply #92 on: September 04, 2020, 10:02:31 AM »
Call me lazy for not going back and reading all the prior posts...

Usirus, if the crossing was done in a controlled way with proper methods to exclude contamination, there would be no doubt about whether the seedling is a hybrid, no?

If so, what are your impediments to making sure there is no contamination? I've never tried it and I agree that there would maybe always be a sliver of doubt in your mind, BUT it seems like it shouldn't be too hard .... (experts, feel free to destroy my naivete :))

Guanabanus

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Re: Cherimoya/Pawpaw hybrid
« Reply #93 on: September 04, 2020, 01:23:07 PM »
There is evidence, that certain conditions can occur, in which a flower literally self-pollinates;  so, careful prevention of contamination from the outside, though the main concern, is not a guarantee.

There have been multiple instances of plant breeders of good repute actually growing out plants that were eventually identified as not being hybrids at all.
Har

Triloba Tracker

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Re: Cherimoya/Pawpaw hybrid
« Reply #94 on: September 04, 2020, 01:37:31 PM »
Makes sense, Har - good to know!

Caution is always a good thing when dealing with plants, it seems.
Thanks!

usirius

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Re: Cherimoya/Pawpaw hybrid
« Reply #95 on: September 04, 2020, 05:05:33 PM »
@TrilobaTracker and @Guanabanus- Thank you for your contributions and thoughts. Well, I have excluded 99,9% of external influences, because on the one hand the flowers have bloomed single and on the other hand I have protected them against possible cross-pollination by insects with a microporous bag. If self-pollination has occurred, it is something I had no influence on, and I do not want to exclude it, and that is - if the seedlings are not hybrids - with 99,9% probability. But what makes me positive is that by varying many parameters I was able to optimize - beginning by the selection of the optimal pollen donor for pollination up up to more and more refinement of the process steps and boundary conditions to achieve the greatest possible probable pollination success, and this reproducible. This means, that there are many important things you have to pay no attention to, and here the right time of pollination is the least problem. Then I also noticed that there is a clear difference between pollinating Cherimoya flowers with cherimoya pollen and pollinating Cherimoya flowers with Pawpaw pollen. If Cherimoya flowers are pollinated with Cherimoxya pollen, it takes a few days and you can see that the pollination is successful and the ovary grows. If Cherimoya flowers are pollinated with Pawpaw pollen, it takes weeks and you get the impression that the plant is thinking about whether this was a pollination at all. And during this time most pollinated ovaries fall off. And a few of them, after several weeks, begin to decide to stay on and grow very slowly. This could be an indication of meiotic chromosome duplication without cell division. I can say more if the seedlings are in an older stage. At the same time I am also producing the inverse hybrid on Pawpaw as mother plant and I have also some more this year's fruit sets with pollination by Pawpaw pollen on the Cherimoya mother plant, which are a bit bigger than pinhead size.
« Last Edit: September 05, 2020, 01:53:44 AM by usirius »
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micawi

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Re: Cherimoya/Pawpaw hybrid
« Reply #96 on: September 04, 2020, 05:28:15 PM »
keep us posted

CherimoyaDude

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Re: Cherimoya/Pawpaw hybrid
« Reply #97 on: September 04, 2020, 08:04:20 PM »
Is there a way to genetically test the leaf? Maybe some university nearby that has something that could count the chromosomes?

Gogu

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Re: Cherimoya/Pawpaw hybrid
« Reply #98 on: September 04, 2020, 10:09:56 PM »
This is super exciting stuff. Thank you for doing this experiment.

Guanabanus

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Re: Cherimoya/Pawpaw hybrid
« Reply #99 on: September 04, 2020, 10:52:08 PM »
That delay in fruit-set development is very interesting!

I don't recall having observed that.

I did sometimes observe the opposite, where foreign pollinations would be rejected so fast that there seemed to be an allergic reaction.
Har

 

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