„Hybrid (Unshiu x P. ITSZ Prague“ is the greatest mystery among citruses for me.
Is it a hybrid? Is that a chimera? Or maybe something else? Any mysterious play of nature? I do not know.
Many of the previously published information I have discovered. Here I will try to summarize the most important thing about this cultivar I know.
1981:
I started growing citrus
1987:
The first literary reference to the hybrid. "Citrus Growing", c. SZN 1987, Ing. Stanislav Husak, CSc., Doc.Ing. Vladimír Táborský, CSc., Prof. Ing. Pavel Valíček, DrSc., Page 21 - 2.2. Fundamentals of genetics and citrus breeding. Photo 45: "Hybrid (Unshiu X Poncirus trifoliata) bred on ITSZ Praha".
It must be said that this was the first and at the same time the last mention of this hybrid in literature in the Czech Republic.
Note: : Prague is the capital of the Czech Republic. ITSZ is a university. Her name is the institute of tropical and sub-tropical agriculture.
Previously, many books on citrus growing have been published in the Czech Republic. Until 1993, a magazine on citrus growing was published- 5 times a year. The Citrus Growers' Association had 10,000 members (the population of the Czech Republic is 10,000,000 people !!!). In a country where citrus trees can not normally be grown !!
Why it was not published anywhere else is a mystery to me.
1989-1996:
I have seen hybrids several times but Cold Hardy citruses were outside my area of interest. I also met with many interesting hybrids, mostly from the former USSR.
I've heard it repeatedly : Badly growing. It does not produce. If you want the weeds in the greenhouse, grab a bud.
2004: Mr. Zdeněk Černoch began to make his collection of citruses, which now belongs to one of the largest in Central Europe. Especially cold hardy citruses. Aroused great interest in them in the Czech Republic.
2007:
I was also interested for cold hardy citrus. The source of grafts was mainly Broža Petr and Zdeněk Černoch. The Bud from which my plants originated was taken by Peter Broža. From its small 15cm large plants growing in the middle greenhouse.
2009/2010:
Plants at Petr Broža and Zdeněk Černoch died in the winter. They have recovered from me. All plants sold by Zdeněk Černoch all over Europe from 2010 until 2014(?) they're out of my buds. Sometimes later, Zdeněk Černoch brought the other buds from France. I do not know from whom.
2016:
I managed to contact Prof. Ing. Pavel Valíček, DrSc., Author of the book from 1986.
He told me that the hybrid was bred prof. Pospíšil. Classical crossbreeding and subsequent selection. Sometime between 1971 and 1977.
Prof. Pospisil is unfortunately dead.
My friend in Prague visited Mrs. Rozinková, who was a collaborator of prof. Pospíšil. She's an older lady, no new information more. She just confirmed the information from Mr. Valíček. The new information was just that there were also experiments with seed irradiation and any others
From information from Petr Broža I know that B. Voss was wearing some citrus from ITSZ greenhouses in Prague. Whole plant with roots. It was supposed to be the hybrid Uhshiu X P.T. ITSZ Praha. It is certain that many other similar hybrids originating in the former USSR were in the ITSZ greenhouses at that time.
Information from Mr. Hlaváč (Head of ITSZ Greenhouses in Prague) - He confirmed that B. Voss took some citrus plant from the greenhouse. It was not a hybrid but something else. The original plant is still growing in the greenhouse of ITSZ Praha. If I want to, I can come and see.
Meanwhile, I did not have time for this (greenhouses are not publicly accessible, the visit needs to be arranged in advance).
In 2016, I accidentally managed to provide at MU Brno (Masaryk University, the Faculty of Natural Science) a cytometric analysis of the genome size of the hybrid. Incl. comparison of genome size Unshiu and P.T and F.D.
The analysis was repeated three times using different parts of the hybrid tissue. For all samples, only one peak was found in the histogram. This means that the plant has only one genome, ie. the plant is of hybrid origin. The chimera should have two peaks in the histogram because it carries two different genomes. Separately tested parents of the hybrid have the genome size significantly different, the histogram would be clearly visible.
However, cytometric analysis of the genome size can not be, for many reasons, a 100% result.
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For different growers, the hybrid is completely different.
The Sylivian plant grows almost up. My plant a willow. Without counting the height of rootstock, they are approximately the same size. I have to constantly shape the plant. Otherwise, it would look like the second and third my plant that crawls 40cm above the ground.
My and other known breeding plants are free of seeds. Sylvian seed produces.
For me, Bi- and Tri-foliate leaves fall in autumn only in older plants, not in young ones.
Sylvian plant blooms in spring twice, my only once.
My plants show mild symptoms of psoriasis or leprosy. But psorosis or leprosy is definitely not.
At Sylvian seedlings produce non-trifoliated plants. I wanted to verify this very much. Except for natural pollination, all the flowers were artificially pollinated. No seeds. Not a germ.
The plant in Vienna transforms itself into a pure trifoliate.
It is totally crazy.