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Use of induced apomixis in the breeding of figs

Thank you Vladis! It is going to take me a while to digest that, but on my initial reading I found some interesting points.

"Most prone to the method of reproduction were apomictic cultivars figs, fruit-usually in the presence of cross-pollination and fertilization [ie smyrna]. Only one parthenocarpic sorta- "Kadota" was found a tendency to induced [apomixis]"
I wonder how many of the varieties tested were common figs, and if we will be able to find any more that will produce apomictic seed.

Greg, I think this gives the answer to one of your questions, but I'm not sure what the answer actually is. Google translate is failing me here ;) 
"In the study of the biological characteristics of individual varieties of seedlings apomnktncheskih " Kadota "it turned out that the property to develop narteiokarpncheskie fruit proyavilos- only a small part of the plant (10%). The rest of the seedlings did not show such a tendency. In the variety " Sarylov "part of the seedlings was prone to partenokarpncheskomu development of the fruit, while the mother plant and its hybrid forms of this ability is not. Thus the property of sa-moplodnostn taking place at the initial variety, may have apo-.miktnchsskih seedlings did not appear, and vice versa, in some part apomnktncheskih seedlings samobesplodnogo varieties can be found penchant for partenokarpni."

Vladis, could you tell us if the apomictic seedlings of kadota or the smyrna figs produced offspring that were common figs (don't need the wasp)? This is the russian:
При изучении отдельных биологических особенностей апомнктнческих сеянцев сорта « Кадота » выяснилось, что свойство развивать нартеиокарпнческие плоды проявилось- лишь у небольшой части растений (10%). Остальные сеянцы не проявили такой склонности. У сорта « Сары лоб » часть сеянцев оказалась склонной к партенокарпнческому развитию плодов, тогда как материнское растение и его гибридные формы такой способностью не обладали. Таким образом, свойство са-моплодностн, имеющее место у исходного сорта, может у апо-.миктнчсских сеянцев не проявляться и, наборот, у какой-то части апомнктнческих сеянцев самобесплодного сорта может быть обнаружена склонность к партенокарпни.

So the crux of this is that the progeny displayed traits the parent did not, and traits different from each other. So the agent or the process is turning genes on. I wonder if just the mechanical irritation of getting hit with a foreign pollen tube can initiate apomixes. I also wonder if the mutagenic properties of the agent cause the variation. This paper sure raises way more questions than it answers - and that's a good thing.

Dale, the progeny display differences from the parent because they only have half the genes that the parent has and each seedling has a different mix of the half that it got.  Because of that there is no blending or dominance of traits from having two different genes for a trait....now the resulting seedlings will have two genes for each trait that are identical.

In this process the parent's pair of chromosomes line up with each other, undergo crossing over (where the parent's pairs of chromosomes blend a bit), and then the pairs get pulled apart so there is only one of each of the 13 chromosomes that make up the diploid reproductive cells.  Normally upon pollination the pollen brings it's own set of chromosomes and the resulting seedling ends up with 13 pairs of chromosomes like the parent (the haploid state where for figs 2n = 26).  But in this apomixis condition the pollen is incompatible and does not supply chromosomes so the egg is left with only the single set of chromosomes from the mother.  However, something from the foreign pollen or chemical they used causes the egg to copy it's single set of chromosomes so that there are 13 pairs of identical twin chromosomes which gives the cell the 26 chromosome haploid state.  It then grows into a haploid seedling.  In effect it sheds a great number of the parent's genes, with each resulting seedling loosing different genes and therefore resulting in genetically unique seedlings.

The paper also did mention some mutagenic properties noted when chemicals were used so that a few new gene modifications resulted.  But for the most part it's just the loss of genes from the parent that creates the changes to the progeny.

Greg,

   Thanks. I didn't get that they were haploid. I didn't think they would be viable at haploid numbers, but that sure explains the variation. So do these plants ever undergo meiosis? What do their gametes look like? What's the critical number of chromosomes for viability, and which?

Greg, the paper does claim the seedlings are diploid. What you are saying makes sense, but with my limited understanding I can't quite reconcile the two. Are you saying they are only diploid in the sense they have 26 chromosomes, and functionally haploid because it is just a double set for the egg?

I think I wrote that post too early in the morning!  The paper says the seedlings are diploids...but they get to the diploid state by first undergoing standard meiosis to the haploid state, then the chromosomes get doubled to become diploids (the "post-reduction doubling").  Sorry for the confusion Dale.  I almost went back and edited my post to clean it up a bit, but figured I'd leave it like that so folks know what you were asking.

Andy, yes, but I'd phrase it as they are diploids, but because the chromosome pairs are identical they are homozygous on all loci.  I'm not 100% certain that that's what's happening, but that's my best guesstimate from the paper's description.  It explains why this method produces variable seedlings and why it's a strong method for finding recessive genes, but I'm not quite certain why the next generation becomes weaker because I would assume that the F2 generation would then end up identical to the F1 generation.....????  Very odd to me.  If anything I'd expect that to happen for the mutagenic compounds rather than non-mutagenic foreign pollen (if that is true).

Hi,
Just have a look at : http://waynesword.palomar.edu/arbimg10.htm#persistent 

So to make it short : My seedlings are from a common figtree so a persistent one so a "P+" tree .
My common figtree will generate "P" and "+" alleles so with apomixis the theoretical results is : "PP" and "++" seedlings ... ... ... Bouhouhouhou ... "PP" is lethal so I'm left with "++" only ... Bouhouhouhou ... Smyrna Seedlings only !!!
Tell me something is wrong and my seedlings will behave and be like their parent or a clone of the parent ... A common figtree ...  Well, ok, time will tell ... if I don't kill the seedlings before :) .

Hi Jds,
You are right, it is quite possible that apomictic seedlings from a common fig will not produce trees with persists fruit. The second paper that Valdis posted seems to indicate they might, but the transition was not good enough to really understand what they were saying. It will be very interesting to see what your seedlings turn out to be.

What was the parent variety of your seedlings?

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