Tetraploid Satsuma

[Skandiberg]

Hi all and Happy Holidays,

I accidentally ran into an article that I found interesting:

https://www.mdpi.com/2073-4395/11/12/2441

A tetraploid seedling of Ishizuka Wase was found, then they grew it to fruiting stage and began to evaluate it. On paper, tetraploid should mean more vigor, bigger leaves etc. and most importantly, better hardiness. And this one has fairly fertile pollen which is not common among Satsumas. So I wrote to them and asked them about this plant. I had never heard of Ishizuka Wase before. Much to my surprise, I got a reply this morning:

'・About cold resistance
We have not conducted detailed tests on the cold resistance of this tetraploid, so we cannot answer your question about its cold resistance.
When observing the cultivation of this tetraploid in the field, it grows a little more vigorously than diploids.
As the climate warms, the cultivation area of Satsuma mandarin is moving further and further north in Japan (southern Tohoku region of Japan, latitude about 38°C).
I believe that the tetraploid has the same or even better ability.
Moreover, the quality of the tetraploid is inferior to that of the diploid.

・About ‘Ishizuka Wase’
'Ishizuka Wase' is a bud mutation of 'Okitsu Wase' and is a fairly minor variety.
'Ishizuka Wase' ripens a little earlier than the major Satsuma mandarin varieties 'Miyagawa Wase' and 'Okitsu Wase'.
There is no significant difference in fruit quality between these varieties.

・About breeding
We are not conducting any research other than the crossbreeding experiments presented in the paper. Research has been halted due to various circumstances at our laboratory (cultivation space, costs, etc.).'

Why they didn't test its hardiness is beyond me. But the overly viable pollen is a standout feature. I will write back to them. I hope that plant is still alive. I wonder what has become of its crosses they made. Not that we have any reason to believe this tetraploid Satsuma will ever get to Europe. ☹️

[Ilya11]

If they were kind enough to take the trouble to answer you, why not to ask for polyembryonic seeds of this tetraploid arising from crosspollinating?

"Moreover, seeds of the tetraploid Satsuma mandarin were polyembryonic."

[Skandiberg]

Exactly! I will report if I get any further positive answers.

[Skandiberg]

Well, they didn't react to my seed request, instead they kindly recommended doing it myself. I did a quick search and much to my surprise, I found a pill available to the public that contains colchicine so I think I will give it a try next year on early Satsuma seeds, if I find any.

But they attached two documents on the process and at least they took the effort to reply. This is a lot further than I got with Chinese universities who just don't give a damn.

[Ilya11]

If you germinate enough seeds of satsuma, there is quite a big chance to get a spontaneous  tetraploid.

[Skandiberg]

Yes, they also wrote that, extending it to all polyembryonic Citrus. But Satsumas don't have too many seeds to begin with. Anyhow, I will buy a few kilos of Satsumas next autumn and see where I get. I found a seed in a Zorica fruit and as dumb as I am, I didn't sow it.

By the way, I have already read the first document they attached about an experiment they did and it was interesting indeed. It's about inducing tetraploid Meiwa, Marumi and Fukushu kumquats and surprisingly, they had a somewhat different behaviour. Marumi was the odd one and they came to the conclusion that it might be because the Marumi cultivated in Japan is mainly polyembrionic while the ancient Chinese strain is monoembryonic. I didn't even know that.

[Ilya11]

Nucellar seeds in satsumas are induced by foreign pollen. In Japan many early ripening varieties were produced by pollinating satsumas with poncirus.
They, like tetraploids arise from somatic mutations in nucellus cells.
Poncirus pollen was used in order to be able to discard  the hybrids by leaf morphology.
You can get a corresponding pdf by search with "CITRUS BREEDING AND BUD SELECTION IN JAPAN"  and getting it from Florida Oneline journals. For some reasons it can not be accesed  by a direct link.

[Skandiberg]

Thank you for the info Ilya, I found the pdf. I will read it on the way home.

After reading the second document they sent me, I will try to find a link to them online and make them available.

The first one already has some takeaways for me. Tetraploid fruit is usually of inferior quality for whatever reason. And the fertility of pollen is generally lower in tetraploid varieties vs. the normal diploid ones. But Marumi had much more viable pollen as tetraploid than diploid, and the original article I linked also reported better fertility for that Satsuma. So the best way to put it is tetraploid pollen has a different fertility than the normal diploid, for better or worse.
These are useful information but I still can't imagine why they didn't test those plants for hardiness.

I will be back with links to the articles tonight.

[hardyvermont]

A researcher from University of Florida said that tetraploid citrus would be more sensitive to drought conditions.  The larger xylem cells would be more likely to get air in them and be permanently unable to transport water to the leaves.  Standard citrus seems to be susceptible to this problem when first getting established. 
Some crops such as strawberries have higher chromosome numbers.  Crossing tetraploid citrus with each other could increase the possibilities for new and improved qualities.  The breeding of tetraploid daylilies has introduced never before seen flower colors and shapes.  Perhaps that could happen with citrus, including more hardiness. 

[Skandiberg]

Hardyvermont,

Thanks for the info! Yes, tetraploids can open up some new possibilities in hardy Citrus breeding.

And I highly recommend the pdf that Ilya wrote about. It seems that even the nucellar Satsuma seedlings aren't always true to their mother but often prove to be slightly different mutations which happen a lot more frequently than you would think. The only downside of it is you have to raise them until they show their crops. Interesting anyway. I don't know too much about the genetic background of plant breeding but these articles are very enjoyable.

By the way, here are the ones sent to me by the Japanese breeders.

https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://www.jstage.jst.go.jp/article/jsta/66/2/66_51/_pdf&ved=2ahUKEwifvuzl48iKAxUJ87sIHSu5DEwQFnoECBsQAQ&usg=AOvVaw3cosfXQg2XxxNqw0Tao_xn

https://www.sciencedirect.com/science/article/abs/pii/S0304423818307106

[bussone]

Why they didn't test its hardiness is beyond me.

38 degrees already gets you to between Niigata and Sendai, so you're rapidly running out of extra room to grow citrus, unless you really want to try it on Hokkaido.

[Radoslav]

To create satsuma like, cold hardy hybrid, bendizao mandarin looks more promising as mother plant.
It produces seeds without any problem, fruit looks identical to satsuma.

[Skandiberg]

Thanks for the tip, that's a very good idea! And it's quite hardy by itself already.

Can you tell me when it ripens?

[Radoslav]

End of september.

[Till]

I have read that tetraploid citrus is usually inferior in fruit quality. Nonetheless, I have the idea to make Morton tetraploid. I could imagine that two Chromosome sets of Poncirus greatly improve hardiness. When Prag Citsuma as a chimera is quite hardy then one full Poncirus genome and one full citrus genome in the same cell might lead to similar hardiness. I would at least like to test it. It could of cause also be that the reduced drought resistance of tetraploids is detrimental to hardiness.

I want to learn the handling of Colchicin anyway. I want to apply it to certain old Russian Sorbus hybrids in order to make them more fruitfull. Tetraploid Sorbus (and Aronia) produces apomictic seeds, and better developed seeds will most probably lead to more fruit set. I think, by the way, that apomictic seeds in tetraploid Sorbus have nothing to do with that tetraploid Satsuma being more fruitful. I think it is a special feature of Sorbus and Aronia (which are closely related).

[Skandiberg]

Till,

I have read the same. But I think it would be worth trying to see if a triploid or tetraploid mandarin has a few degrees more hardiness, even at the cost of losing some of the fruit quality.

Colchicine is not available here. There is some medicine that contains it but it can be bought only for prescription. So I must try ghibberellic acid which can also be applied to that purpose. And this morning I ran into a study that was about shortening juvenile phase in Citrus seedlings. Ghibberellic acid and benzyladenine were mentioned, in conjunction with the amount of temperature and light.

Ghibberellic acid is freely available so I ordered a pack of it. Some experimenting can do no harm. I have a pot of Nova mandarin seeds that haven't germinated yet so I will apply it on them.

[sc4001992]

Iilya, I have to agree about seeds in satsuma.

"If you germinate enough seeds of satsuma, there is quite a big chance to get a spontaneous  tetraploid."

I have 2 older satsuma trees in the family and each tree has about 2,000 fruits each year. Out of those fruits, I might see 1% of the fruits with a seed so it's not that easy to get seeds to grow out.

[Ilya11]

You can increase the number of seeds in satsuma by forced pollination with poncirus. The resulting hybrids can be discarded on their trifoliate appearance. Also, usually each satsuma seed gives at least 3 seedlings.

[Ilya11]

Skandiberg,
I am not sure that is is easy to produce polyploids with gibberillic acid.
There is another substance that is widely used to this : herbicide oryzalin.

[Skandiberg]

Ilya,

Thank you for the tip! I will check what that is. I haven't heard of oryzalin.

[Peep]

I have 2 older satsuma trees in the family and each tree has about 2,000 fruits each year. Out of those fruits, I might see 1% of the fruits with a seed so it's not that easy to get seeds to grow out.

Recently I was given some Satsumas by a friend, it was about four fruits, five at most. And from memory, at last two had seeds, and I believe more than one seed (but two or three seeds at most).

So it seems it's possible to get Satsumas with more seeds. They came from a variegated Satsuma tree, I don't know if that has anything to do with it.

[sc4001992]

Ilya, ok, I can try that this year when the satsuma trees flower. There is a large poncirus tree next door that I can use pollen. So which seedlings are good to keep, the ones not showing any trifoliate appearance?

[Ilya11]

sc4001992,
Exactly, zygotic seedlings with trifoliate leaves should be discarded ( at least for the purpose of getting tetraploids  )

[sc4001992]

ok, thanks.