Breeding Targets and Techniques
The composition of the essential oil with varying percentages of bisabolol, bisabololoxide, bisabolone, and matricine is fixed genetically. Schick and Reimann-Philipp remarked in 1957: “As far as breeding is concerned Matricaria Chamomilla has not yet been worked on.” In 1950 only the two group varieties “Quedlinburger Groβblütige Kamille” (Quedlinburg large-flowered chamomile) and “Erfurter Kleinblütige Kamille” (Erfurt small-flowered chamomile) were mentioned. Often the stability, the resistance against diseases, the germinability, the flower yield, the fact that the individual flower heads are ripe at the same time, the homogeneous flowering horizon, the stability of the flower head, and consequently the suitability for a mechanical harvest are not sufficient. Since then a rapid development has been experienced. A number of chemotypes with a varying content of matricine / chamazulene, (–)-α-bisabolol, spiroethers, and the bisabolol oxides A and B as well as bisabolone oxide A were selected. Varieties with very different breeding targets were bred. The content, especially the composition of the active principles, was worked on by precise selections. For nondestructive characterization of valuable substances in chamomile single plants, a near-infrared (NIR) spectroscopical rapid method is available.
Some of the present breeding targets are (sequence does not mean order of priority):
- High yield
- Large flowers
- Compact flower heads
- Stability of the flowers for a mechanical harvest with a low percentage of stems
- Regular growth with basilar ramification and many flowers (close proportion of herb:flowers)
- Narrow homogeneous flowering horizon
- Uniform flowering time, especially simultaneous ripening
- Good shooting capacity for a high yield with the harvest to follow
- Firm flower head with little inclination of disintegration and formation of fines
- High content of chamazulene (blue oil) >25% within the oil
- High content of (–)-α-bisabolol >30–50% within the oil
- Low or much bisabololoxide
- High content of total flavonoids >3%
- High content of essential oil (0.7–>1%)
- Desirable composition of the essential oil
- High germinability
- Resistance against powdery mildew and other diseases
- Stable stand
Particularly the working group led by Franz has made intense genetical investigations and others). By this research it was proved that medicinally relevant (–)-α-bisabolol is inherited recessively. The formation of the (–)-α-bisabolol oxides A and B is dominant over (–)-α-bisabolol, whereas (–)-α-bisabolone oxide A dominates (–)-α-bisabolol as well as the (–)-α-bisabolol oxide A and B. This is verified by using PCR-based marker techniques like Random Amplified Polymorphic DNAs (RAPDs) and Amplified Fragment Length Polymorphisms (AFLPs) as useful tools for the acceleration and improvement of the breeding process.
Nowadays quite different forms are available to cover various demands. It should be taken into consideration that not all results of these breeding works are admitted as varieties or not all of them can be purchased but often individual firms use them for their internal cultivation to produce special products. A short (incomplete) survey of released varieties and used breeding material is given in Table Varieties and Breeding Material in Chamomile (Matricaria recutita L.), in Table Characteristics of Varieties and Breeding Material in Chamomile (Matricaria recutita L.) some of this breeding material is classified according to its characteristics.
Table Varieties and Breeding Material in Chamomile (Matricaria recutita L.)
|Sregez (17% chamazulene)|
|Chile||Manzanilla Primavera Puelche|
|Czech Republic||Bohemia (2x)|
|Goral (=Kosice II, 4x, high content oil, chamazulene, bisabolol)|
|France||MA.VS.1 (ca. 1% oil, 25% chamazulene, 45% bisaboloxid A/B)|
|Hungary||Budakalszi 2 (=BK2,4x, high content oil, chamazulene)|
|Soroksari 40 (2x)|
|Poland||Zloty Lan (4x, high content of oil, chamazulene, low bisabolol)|
|Slovak Republic||Bona (2x)|
|Goral (=Kosice II, 4x, high content oil, chamazulene, bisabolol)|
|Spain||Adzet (2x, bisabolol)|
Table Characteristics of Varieties and Breeding Material in Chamomile (Matricaria recutita L.)
|High matricin-/chamazulene and bisabolol||Adzet|
|High matricin-/chamazulene and bisabololoxid||Bodegold|
|Budakalaszi 2 [BK 2]|
|Argentina (usually bisaboloxid B)|
|High matricin-/chamazulene and bisabolon||Lazur|
Most of these are realized in tetraploid varieties. When choosing the breeding place as well as the company for seed multiplication and maintenance breeding, this should be done with care. In case of a contamination of the soil by chamomile seeds (wild growing or cultivated populations some years ago) a crossing of tetraploid and diploid chamomile takes place. A clear separation by mere sifting of the (mostly) bigger tetraploid seeds is not possible. As a large amount of chamomile seeds is found in the soil of the cultivation areas and as there is no reproductive isolation in respect of wild chamomile, it is impossible to cover the next year’s seed requirements from normal material of cultivation being mostly still the case with traded material from Egypt. The multiplication of seeds has to be regulated by taking suitable steps of organization and agrotechnical measures. For this purpose the basic material has to be produced from individual plants by partly taking in vitro multiplication steps. The seeds on hand are more or less treated as a hoe culture to make sure that no unwanted chamomile can contaminate the seeds. If the multiplication of seeds is done properly there is little danger of hybridization even with diploid chamomile, so that this supposed advantage of tetraploid chamomile does not seem to be relevant in the main cultivation areas.
With the breeding at a diploid stage of valence, in Germany for instance, the first step was a selection on an early flowering time on relatively shortened long-day terms. In the breeding pattern individual plant selection from more than 10,000 plants of an Argentinean population in connection with diallel crossings, backcrossings, and in vitro cloning was applied. By means of thin-layer chromatography a preselection of plants of suitable qualitative composition was made. After the in vitro phase the clones (adapted to substrate culture and recultivated) were planted on plots of comparison at two places in four repetitions, then they were tested on susceptibility to diseases and finally the oil content and the oil composition was determined. So the material could be restricted to a great extent.
After the calculation of suitability for combination according to method II, model II, on the basis of the parents and F1– descendants kept in tissue culture further seven diallel crossings of the suitable clones were carried out, which were multiplied again by a tissue culture before. The crossing partners ceased flowering isolated from the other crossings. From each crossing about 15,000 plants could be cultivated, which were planted into fields of 500 m2 each with a distance of normally several kilometers from each other. A hybridization of wild material was prevented by protective sowings such as by a broad belt of maize or cereals and by control of the surrounding fields on wild chamomile. Any unsuitable plants were removed by negative mass selection. With the crossing descendants from bisabolol-azulene parent plants, the bisabololoxide A-azulene parent plants and the bisabolol oxide B-azulene parent plants backcrossings were carried out with the maternal parent from the in vitro depot.
Selections from the book: “Chamomile”. Edited by Rolf Franke and Heinz Schilcher. Series: “Medicinal and Aromatic Plants — Industrial Profiles”. 2005.