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The True Polyembryonic answer.....

Posted by mangodog palm springs (My Page) on
Tue, Nov 30, 10 at 15:20

so.....I'm trying to understand growing mangos from polyembryonic seeds and have checked the past comments on this forum and read these two opposing comments:

.....from Simon Gro back in October. "Newbies like me have to remember that the polyembryonic mangoes produce clones but also at least one zygotic seedling that will not be a clone. From what I remember reading, the strongest fastest growing sprout is likely the zygotic seedling and thus not the clone. Just to be safe, its probably smartest to grow up at least two seedlings from any polyembryonic mango seed".

Then from Mango Joe in May of this year(some kind of genetic researcher in Guatemala) "More traditionally and without the use of expensive means to attain proper identification, (this technique is used all over the world in developing nations) about 30 - 45 days after a poly-embryonic seed germinates, the 3 - 8 seedlings are reviewed. Zygotic seedlings tend to grow with less vigor and seem to be less healthy looking on first appearance than the nucellar seedlings. At this time, the farmers will remove the seedlings who appear to be weaker and "pot-up" the stronger looking ones to later plant in the field or less commonly for rootstock. The success rate of this is amazing, especially in Asia where the greatest abundance of poly-embryonic mangoes are grown."

so.....without any disrespect to the quoted gentlemen above, can we get a definitive answer? Is it the stronger or weaker seedling(s) of a sprouted polyembryonic seed that is/are true to its parent? (Would slso love to see a pic of a sprouted mango poly-seed if anyone has one, in order to see this demonstrated....)

Many thanks, amigos.....mangodog


Follow-Up Postings:

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RE: The True Polyembryonic answer.....

I searched for this answer and I have a feeling its not as straightforward as I once thought


from the link below:

Mango possesses either polyembryonic (apomictic) or
monoembryonic seed (Bally, 2006). A polyembryonic
seed contains two or more embryos and they are zygotic
(sexual) and nucellar (asexual or maternal) embryos.
Monoembryonic seeds contain only a single zygotic
embryo (a cross between maternal and paternal parents
that is nurse or zygotic seedlings). According to Bally
(2006), zygotic and nucellar seedlings are both used as
rootstocks. The use of nucellar seedling rootstocks would
ensure fruit orchard uniformity unlike nurse or zygotic
seedlings. Nucellar seedlings are identical to the parent
plant (Xiang and Roose, 1988; Garcia et al., 1999; Ruiz
et al., 2000), but differences could be due to somatic
variations (Frost and Soost, 1968).
Identification of zygotic seedlings (referred to as offtype)
from nucellar seedlings (true to type) is important
for maintaining genetic homogeneity which ensures field
uniform performance of rootstocks (Rao et al., 2008).
However, this has not been easy in many polyembryonic
seeds (Frost and Soost, 1968) and this includes mango
seeds. Identification of the two types of seedlings
requires the use of genetic markers, but the use of these
markers can be expensive, especially for many local or
ordinary nurseries.
The use of nucellar seedlings can increase the availability
of rootstocks unlike zygotic seedlings. The polyembryonic
seeds produce numerous nucellar seedlings,
although distinguishing nucellar from zygotic seedlings
has been a setback. At Pedro Sanchez (Snr) research
nursery of the World Agroforestry Centre (ICRAF) in
Makoka nursery, remarkable differences in mango seedling
emergence and growth has been observed. The first
or early seedling to emerge per seed has been taller and
thicker than late emerging seedlings. It was assumed that
most of the late emerging seedlings were nucellar since
they were numerous. It is unlikely that a polyembryonic
mango seed can produce as many zygotic seedlings as
nucellar ones. According to Bally (2006), only twin or
triplet zygotic seedlings can be produced from a single
mango seed in rare cases.

Here is a link that might be useful: http://www.academicjournals.org/AJB/PDF/pdf2010/1Mar/Mng%E2%80%99omba et al.pdf


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RE: The True Polyembryonic answer.....

egaads.......

well, what i gleaned from your article mango-K is that in most cases the Zygote(s) tend to emerge first and usually one with rarer occurences of 2 or 3. Apparently, the most numberous sprouts coming from a seed and the ones that start a bit later are the nucellar (or exact parent type).

A dilemna that seems to remain is what Mango Jim was saying above, "the strongest seedlings were taken as nucellar and the weaker as Zygote...." while in your attached article it was noted: "....orange zygotic embryos are large and occupy the most space, while nucellar embryos are tiny..." so size does not apparently predict seedling type according to these two sources....

how depressing!!!!!!!!! I mean if you don't know what you are growing, though it may still turn out to be a tree with great fruit, how does one properly identify to another taking scion wood or selling the fruit, that it realy is what we claim it to be, or any plants that we buy that come from seed and are not grafted.....where is the surety of type?????

thanks MK - wish they had simple DNA testing kits for this stuff.....you know - draw a little blood ( I mean sap!), add two drops and PRESTO - color match!

mangodog


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RE: The True Polyembryonic answer.....

I dont know, you would have to ask someone who propagates manilla seedlings, they have to have a method of distinguishing the nuccellar with some percentage of success.

I was initially told the distinct zygote sprout produced sexually would be more vigorous then the nuccelar clone, which made sense to me from a natural selection standpoint, the more diverse sexually produced zygote sprout seedling would be stronger.


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RE: The True Polyembryonic answer.....

I, too, was also confused by which is the clone/which is the zygote. I figured, if it's not true, then it will be close to being true.


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RE: The True Polyembryonic answer.....

I think the best thing to do is to plant out several of the seedlings/clones and just wait for them to fruit and save the clones or zygotic seedlings that produce good fruit.

I recenlty planted a Champaign mango seed (polyembryonic) and two sprouts are popping out, both the same size. It got hit with frost several days ago but I hope they will pull through. If they make it, I'll post my results although it will still not resolve the issue of the larger stronger seedling vs. smaller weaker seedling being the clone!


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RE: The True Polyembryonic answer.....

oh Simon LeGrow....I may end up having to do that, planting several seedlings and waiting for fruit, but it seems ....I don't know....like blind gardening - no disrespect to those sight-challenged green thumbs out there.....

by the way....does the zygote (that we're not sure is a zygote or not) always represent one of the parent plant's parents or could it be something more like a 2nd cousin or great auntie - lol.....

grrrrrrrrrdoggie


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RE: The True Polyembryonic answer.....

the zygote can be cross pollinated or pollinated by the same tree which would create genetic variability. usually some characteristics are similar but traits like fiber seem to be dominant in my limited experience in wild mangos


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RE: The True Polyembryonic answer.....

"Commercial nursery and NCGR-Miami standard practice involves removing all but the most vigorous seedling germinating from a single seed."

But even using that practice, they found that up to about 1/3 were selected incorrectly depending on the cultivar.

FSHS article

Jeff


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