Drucken

[moreno]

Starting with the idea that any species should benefit of the genetic exchange that occurs through the meeting of two different types and then, on the contrary, a continuous reproduction between subjects of the same kind can produce weakness and pathologies, I was wondering, which problems can have the plants that we get by asexual reproduction (eg division,cuttings,etc.)?

[partisanengärtner]

Pest will have easy access to uniform plantpopulations. It will depend on the number, the clones will be distributed in

[riesenweib]

one other apsect: only one individual is propagated, the older it is, the more prone it is to diseases (ask the rosarians).
Or (almost) all plants derived from one individual can succumb to a disease. Example is the death of the English Elms (identical clones, to my knowledge, of a Ulmus procera) variety due to dutch elm disease. The story in short here.

[uliginosa]

Well, of course you choose healthy individuals for asexual reproduction in the first place.

There are rose varieties that have been vigorous for centuries and continue to be healthy.

And there are a few rose varieties, that have lost the resistance against mildew, for example. Then you can just stop planting that variety and turn to new healthy ones, that have been bred in the mean time.

_{I wrote this before having read Riesenweib's answer!}

[Staudo]

I understand only railway station.

[Gartenplaner]

Moreno fragt sich, welche Probleme bei klonaler, ungeschlechtlicher Vermehrung von Pflanzen über lange Zeiträume auftreten können.

[pearl]

Starting with the idea that any species should benefit of the genetic exchange that occurs through the meeting of two different types ...

the question is, why had sexual reproduction did occur in the course of evolution? And why was sex so widely practiced? In principle, it is not necessary to exchange genetic information between individuals of same species to be successful in life.

There ist no risc of beeing "degenerated" or that genetic material spoils during reproduction undergoing only mitose cycles. The ability to check and repair DNA mismatches and wrong readings is great in all organisms.

[pearl]

... and then, on the contrary, a continuous reproduction between subjects of the same kind can produce weakness and pathologies, ...

to second part of this post, the continuous selection of individuals of one species after crossing back to get one, two or three specific qualities, like tall, white and double flowers, will generate individuals, that have lost ecological capacities to survive in suboptimal conditions.

That is the reason why we have plenty of those big, sensational und double flowers under optimized cultivation conditions in good ground with kompost. Those plants are not qualifying as neophytes, they will die in the wild.

[pearl]

... I was wondering, which problems can have the plants ... by asexual reproduction ... ?

coming to the third part. A lot of plants practice dominantly asexual reproduction. There is no reason to expect problems plants will have making runners and forming ramets. Asarum europaeum, Ajuga reptans, Fragaria vesca and lots of grasses in meadows are genets. There is no loss of genetic information.

Sexual reproduction is time and energy consuming and in some situations it is more efficient to cover the ground with a clone beginning with one individual. Supposing the habitat has constantly the same environmental conditions, then such asexual reproducing plants have very much success. In cases the environment is heavily disturbed, then the chance of offspring coming from seeds resting during the unconfortable times in the ground has more advantage.

[pearl]

... I was wondering, which problems can have the plants that we get by asexual reproduction (eg division,cuttings,etc.)?

problems with cultivated plants that has been propagated with cuttings may have several reasons.

propagation of diseases, the cutting may not be clean und sterile. Over a long timescale there may be accumulating pests. Virus infection is most potent to kill plants in such cases.

Cuttings of flowering shoots may transport the information of programmed cell death. A process under the controll of growth regulators produced during the maturation of the plant.

[Staudo]

In über lange Zeit vegetativ vermehrten Pflanzen „sammeln“ sich latente Viren, Mykoplasmen und andere Krankheitserreger. Außerdem überwinden pilzliche und bakterielle Schaderreger die die Pflanze innewohnenden Resistenzen. Die Sorte „baut ab“. Dieses geschieht allerdings sehr unterschiedlich. Manche Sorte macht auch nach Jahrzehnten noch einen vitalen und gesunden Eindruck, andere Sorten brechen schon nach wenigen Jahren zusammen.

[partisanengärtner]

Die Schokoladencosmee Cosmos atrosanguineus ist ein gutes Beispiel.
Von der gab es bis vor kurzem nur einen einzigen Klon, der zudem massenhaft verbreitet ist. Sie wird zunehmend anfälliger, oder andersrum sie trifft immer öfter auf Krankheiten die schon auf Ihre Abwehr selektiert sind. Ganz abgesehen von Staudos Ansammlung von Pathogenen. Die wären mit modernen Vermehrungsmethoden wohl überwindbar.
Bei Versuchen sie am Ursprungsort wieder anzusiedeln hat sie kläglich versagt. Sie ist dort nicht mehr überlebensfähig.
Es ist aber inzwischen ein fruchtbare Linie aufgetaucht die wieder samenvermehrbar ist.

[riesenweib]

ahhh - danke Axel, das find ich sehr interessant, wusste nur vom sterilen einsamen klon. Werde gleich mal guckeln.

lg, brigitte

[moreno]

First of all, thank you for your answers;
I have come to my question laboriously reading the first few chapters of this book:

http://www.theguardian.com/books/2010/sep/27/orchard-invisible-seeds-jonathan-silvertown

I am fascinated by the subjects of botany but my limited scientific knowledge make it all very hard.However, the book (of which I've only read the first few chapters ) contains many interesting topics that I'm going to investigate .

Another “botanical doubt” occurred to me while I was reading, during the Christmas break , this article:

http://www.rhs.org.uk/Plants/RHS-Publications/Journals/The-Plantsman/2011-issues/March/w-Veg-propn

In particular where it says :

"...the physiological condition of the material is not represented by the immediate age of the individual parent stock, but is a function of the chronological (and physiological) age of the original selection. This is the case however many generations it is removed from the current material. For example, a 10­year­old stock plant of Ribes sanguineum ‘Pulborough Scarlet’ should be regarded as 80 years old because the cultivar originated in the 1930s."

and also:

"... the age of the cultivar determines its potential and relative regenerative capacity (bear in mind that date of introduction is not always a reliable guide; the plant selected as the cultivar may have germinated many years before)."

Could you please explain me this passages, I can hardly understand that… I was wondering, how could the age of the cultivar affect the regenerative capacity of a plant?

(Naturally, your answers are welcome in German as well)

[Quendula]

(Naturally, your answers are welcome in German as well)