MQ · 4
The cultivation of Aztekium ritteri Boedeker by seeds by Andrea Cattabriga
MONDOCACTUS
QUADERNI
Titolo
MONDOCACTUS QUADERNI n. 4
The cultivation of Aztekium ritteri Boedeker by seeds Lecture given at the 22nd Congress IOS, Phoenix, AZ – USA, 5-12 April 1992 Digital repring November 2016. www.mondocactus.com info@mondocactus.com
This work is distributed under Creative Commons License Attribution-NonCommercial-NoDerivatives 4.0 International. 2
Editorial
Aztekium ritteri plants in the 80s of last century were almost exclusively available as specimens reproduced by grafting or wild plants, much sought after on the international market, with the serious risk of impoverishment of the few populations known at that time. Following a simple experiment conducted at home I could see that the reproduction of this species in captivity was possible, although not with the same ease of the majority of the Mexican cacti species. I was then invited by some members of the IOS (International Association for Succulent plant study), engaged in the conservation of plant species at risk of extinction, to illustrate this experience during a conference held in 1992 in Phoenix, USA, demonstrating that also this species could be successfully reproduced in captivity.
The cultivation of Aztekium ritteri Boedeker by seeds.
Preface
Aztekium ritteri Boed. is a tiny mexican Cactus very peculiar in shape, looking like the famous aztek calendar. It’s a plant known for being extremely slow growing and very difficult to be cultivated; for these reasons natural populations have suffered serious damages caused by collectors since the plant was discovered in 1928. During the last years the collecting market demand for plants taken from their natural habitat has been increasing dangerously. Recent regulation activities against the illegal trade of endangered plants have made the amounts import drop. Botanists’ surveys of natural populations located in the most remote places confirmed that at present this species is likely to be preserved. Nursery growth and propagation can contribute to the conservation of the endangered wild plants. In fact the offer on the market of plants grown in pots which are healthier and more adaptable to growing conditions would reduce the collectors’ demand for plants taken from the field.
Purpose of this paper
The purpose of this work is to define a correct methodology to obtain Aztekium ritteri plants by seeds through the use of standardized techniques which allow the evaluation of comparisons and results and make it possible to get the highest yield.
Materials and Methods
I bought the seeds, a stock consisting of 1,000 3 – La coltivazione di Aztekium ritteri da seme
Wild plants of Aztekium ritteri. Rayones, Nuevo León, Messico.
items from several specialized nurseries. The media was made up of three components: peat, calcarious sand and quartziferous sand. The mixture was sterilized at high temperature (200 °C per 30 min.).
Old specimen of A. ritteri in cultivation, probably wild collected.
I used a small tinfoil container sealed with Domopak film. The media was watered by immersion in low salt rate water. The container with the seeds was placed in a glass box (80 cm by 50 cm by 30 cm) equipped with two neon tubes (Silvania GROLUX) 50 cm long and with the power of 18 watt each. The neon tubes were placed at about 20 cm above the soil. The lighting was about 2,500 lux. The temperature was kept at an average of 21 °C. The neon tubes were turned on by a timer set on the actual day length. This timer was adjusted monthly. The conditions were not altered for about ten months and the media was kept well watered by immersion without removing the Domopak film. During the last two months I let the media get completely dry. These last months coincided with the end of winter and the tinfoil container was moved from the glass box to the greenhouse. The lowest temperature in the greenhouse was 16 °C. The tinfoil container was watered and the Domopak film was removed. It was placed in a polystirene container which was much larger and covered with a polycarbonate sheet. The plants 4 – La coltivazione di Aztekium ritteri da seme
lived under these conditions until the next year when they were transplanted (their size was about 2.5 mm). About twenty of these plants were left on their own roots whereas about 100 of them were grafted on Myrtillocactus geometrizans has been obtained by seed and therefore were regarded as more productive and more disease resistant. The nongrafted plants were placed in soil made of clay, crumbled mineral gypsum and limestone. The choice of the plants to be grafted was random. Some plants were grafted on other species such as some of which, in their turn, had been grafted on Opuntia ficusindica.
4. Results 4.1 General results The seeds germinability was about 80%. Germination started one week after the sowing and ended several days later. After one year the survival percentage was about 45%. After transplantation, the plants surviving were about 80%. The grafted plants reached their reproductive
4.2 Observations on the rootstock yield I preferred to use seed obtained rootstock plants because they are considered to be lasting, diseases resistant (especially roots rotting resistant) and because through the use of young specimens, it’s possible to give a remarkable though not excessive boost to growth. Among all cactus generally used, I chose Myrtillocactus geometrizans because of its fast growth rate, of the availability of seeds and the easy of handiness. A drawback of this species is its sensitiveness to temperatures lower then 0 °C. Plants were used when 10 cm high (two-three years old). We tried to use harder and bigger rootstock, like Trichocereus pachanoi 30 cm high, but Aztekium grafted plants suffered a lack of nutrition because the rootstock continuously produced offsets. 4.3 Observations on plants’ variability Within grafted plants population we have observed a sensible phenotypic variability, especially as to number of ribs and interribs, spines shape and length, areole shape and their density on the ribs, number of offset produced, pigmentation, diameter and flower size, shape and color. Some of these characters are mainly genetically controlled, others are determined mainly by the environment. We compared the population of grafted plants with the nongrafted and with a group of ten Aztekium plants obtained from a single specimen (monoclonal population) grafted on different Myrtillocactus. From these comparisons it can be assumed that in my populations the mainly genetically controlled characters were: body size and ribs shape; flower and fruit color, their shape and size; areoles size, their density on the ribs and their woolliness; spines length and shape. On the other hand, environmental characters were offsets production and to a certain extent body pigmentation. Seedlings of A. ritteri photographed at various stage of growth.
maturity five years after from their birth. Non grafted plants haven’t reached their reproductive maturity yet (six years after their birth). The differences in diameter between grafted and nongrafted plants are shown below: Grafted plants, Mean= 20.57, Standard dev.= 4.22, Variance= 17.82. Nongrafted plants, Mean= 9.55, Standard dev.= 2.14, Variance= 4.59. The distribution was normal in both cases, in fact: Grafted plant: Student t= 0.7648 Nongrafted plants: Student t= 0.7521. 5 – La coltivazione di Aztekium ritteri da seme
4.4 Pests and diseases The most serious nuisance for seedlings of Aztekium ritteri is the dart fly Sciara sp. whose larvae are able to eat them up. This fly must be kept under strict control because the tiny Aztekium seedlings are in dangerous of being eaten during their whole first year of life. The use of a well sealing Domopak film allows the seedlings not to be infested, it has been observed that a single hole in the film of 1.52 mm in diameter can be sufficient to the fly to come in. Saprophytic fungi and algae can live together with seedlings while some fungi can be deleterious. Moss usually suffers from artificial lightning, and
Above: The same plants of the previous page photographed in 2015 just before being transplanted. Right: Detail.
remain at a micellar stage. Adult plants are sensitive to different parasites attacks. Both grafted and non grafted plants are vulnerable to infestation by root mealy bugs (Rhyzoechus falcifer). Non grafted plants are more resistant whereas grafted plants are vulnerable to attack from mealy bugs (Pseudococcus citri, P. maritimus) and the dangerous red spider Tetranychus sp..
5. Concluding remarks 5.1 production of plants by seeds The production of plants on their own roots by seed seems to be interesting from a commercial point of view. On the one hand this process presents some disadvantages: low productivity rate, long term production (it takes at least 8 years to obtain a plant saleable on the market) and high labor cost due to the difficulties in handling such small size plants. On the other hand it gives plants which can have an easy sale and obtain good prices on the market. 5.2 Propagation by grafting This propagation techniques is based on the cultivation of ‘Mother plants’, grafted Aztekium ritteri which are able to produce a large number of offsets per year, these offsets in their turn, are grafted to be sold. It’s the fastest method to pro6 – La coltivazione di Aztekium ritteri da seme
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duce this species in large quantities, but it is not always successful on the collectors’ market because it is considered as unnatural and vulnerable to rotting. Besides the rooting of a mature grafted specimen is almost impossible. As the nurseryman exploit just one or few ‘mother plants’ to obtain large amounts of saleable plants, obviously only few clones are available on the market. 5.3 Production of seeds-obtained grafted plants This technique increases both production time and costs. Moreover the high variability of the plants obtained makes it more difficult to plan a standardized production. This technique seems particularly suitable to grow a collection of plants with a conservational aim. In fact, as the mortality rate is very low and a high number of different specimen survive, the variability within the population can be maintained at the highest possible level. 5.4 Propagation by offsets rooting Offset rooting may be useful to propagate plants on their own roots, when necessary (for example diseases at the core of a clump or so). It can’t be considered an usual form of propagation, due the high value of clumping specimens. 5.5 Propagation by grafted plants’ offsets rooting To the best of our knowledge no plant which has reached its maturity on a stock has been re-roo8 – La coltivazione di Aztekium ritteri da seme
Above: Second generation of plants propagated by grafting. Below: two months old seedlings 2016.
ted so far.1 This might be due to the fact that the plant is so accustomed to the very high nutrition rate supplied by the stock, that is unable to adjust again to its normal metabolism.
6. Production of seeds
It can be assumed that the maintenance of a collection of different grafted Aztekium ritteri gives the possibility to obtain large quantities of seeds. 1 Since 2010, I obtain rooted Aztekium ritteri plants from shoots of grafted specimens, although this is applied only to specimens that do not hold during graft. The yield is very low, not sufficient to justify the implementation of this practice regularly.
All plants In our collection were marked and each was ‘married’ to one other. It was decided not to separate the partners. In this way the inbreeding will be maintained at the lowest value and the seeds will be at the maximum value of heterozigousys, which theoretically means, the best germination and productivity, and the best conservation of diversity within future generations of plants. Seeds are really tiny and we designed a special aspirator to collect them by suction. This instrument enable us to explore with a thin cane the woolly areoles where seeds are placed and to remove them without damaging the plant apex. The instrument placed aspirated seeds inside a little plastic or paper bag.
7. The others endangered Cactae
The techniques illustrated in this paper have been used to grow by seeds other species, that are known to be particularly difficult, such as Strombocactus disciformis. For most of other species the process is simpler as they don’t need a germination chamber. Currently we are growing all slow growing Mexican endangered cacti by seeds. We just make sure that the pots are properly sealed with a plastic film and the soil is moist throughout the first year. For all these plant, such as Ariocarpus sp., Pelecyphora sp. Turbinicarpus sp. a production cycle of about seven years has been planned.
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MQ · 4 The series “Mondocactus notebooks” collects a renewed edition of the contributions devoted to the succulent plants that I produced from 1983 until today. The text of the articles was deliberately preserved in its original form, so any errors in grammar and concept have not been corrected. For this occasion was also produced this version of the English text, accessible by pressing the [EN] at the bottom right of each page. I apologize for the low quality of the translation, accomplished with the tools available on the internet, but its only purpose is to make the least understandable
by Andrea Cattabriga
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text to an international audience. Reading the various items you can appreciate significant variations of the style adopted from time to time, due to both a gradual maturity of expression, and the need to adapt the contribution to a congress or to that kind of publication for which it was prepared, as the magazine of an association of amateurs, or a commercial journal or book. The purpose of this project is to integrate the general information available on the mondocactus website pages with free downloadable documents on specific topics.