Cytoplasmic male sterility

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As Cytoplasmic -kerngenetische male sterility ( English C ytoplasmatic m ale s terility , CMS ) are maternally inherited mutations referred to different plant species, leading to a degeneration of the anthers ( anthers lead) and thus to male infertility this plant. The genes mutated in CMS are part of the mitochondrial DNA .

CMS is in plant breeding and seed production to facilitate the recovery of the hybrid - seed used ( CMS technique ). In this application, the CMS serves to prevent the self-fertilization of the line intended as maternal . If the resulting F1 hybrid is to be able to fertilize itself (necessary for cultivated plants whose fruits or seeds are used), the male line must have a so-called restorer gene that cancels the CMS again. The result is that the offspring of the crossing partner produce their own fertile pollen again and can thus fertilize themselves and each other again. However, sterility can also be canceled by extreme environmental conditions such as heat, drought or heavy rain.

In some cases, the genes linked to CMS can be introduced using conventional plant breeding methods. Often, however, molecular or cell biological methods such as cell fusion or protoplast fusion are used. The latter are not considered genetic engineering methods and produced organisms are not considered genetically modified organisms within the meaning of the EU Release Directive or the German Genetic Engineering Act , provided that the resulting organism could also have been produced using traditional methods.

history

The discovery of cytoplasmic male sterility goes back to the natural scientist Joseph Gottlieb Kölreuter , who observed the abortion of the anthers . In the meantime, cytoplasmic male sterility has been proven in over 150 plant species. Examples are corn, rapeseed, rye, broccoli, lettuce, cauliflower, kale, red and white cabbage, savoy cabbage, Japanese radish, chicory and carrots.

The first CMS used for breeding purposes in maize, CMS-T, was discovered in Texas (USA) in the 1950s. With the use of CMS-T it was possible to dispense with the separation of the anthers of the mother plants ("detasseling").

Organic farming

According to the legal basis, CMS varieties are approved for organic farming and are also used in organic farming. The associations Demeter , Naturland , Bioland , Verbund Ökohöfe and Bio Austria do not allow the use of hybrids that were produced with CMS technology, according to their own information. In this context, a positive list of cell fusion-free varieties was published in May 2018 . For the members of Bio Suisse , this has so far only been a recommendation. At Bio Suisse, CMS varieties, with the exception of cauliflower (including romanesco , colored cauliflower types ), broccoli , white cabbage , savoy cabbage and chicory , are no longer permitted.

Problems and Risks

Changing environmental conditions can destroy entire harvests and pose great problems for people. Harvests are often decisive for life. People in developing countries are mostly dependent on the income from their life insurance. But the seeds are often so expensive that not everyone can afford them. In many cases, organizations then have to intervene.

In the 1970s there were major yield losses in the USA (loss of 15% of the harvest) because a single CMS system (Texas cytoplasm) was used for 80%, but the weather conditions for the CMS system were too bad and so the harvest restricted.

But entire harvests can also be destroyed in Germany. The CMS method severely restricts genetic diversity because the plants are modified according to restricted quality criteria. There could also be unwanted side effects such as: B. a greatly increased susceptibility of maize to leaf drought fungus. The change in the flowering organs on the plants could have negative effects on insects, which are dependent on the pollen of the plants.

The possibilities of reproduction ( farmer's privilege ) are overridden by hybrid breeding . The F1 seeds must be made anew for each generation. Hybridization is an expensive and time-consuming process which creates a monopoly position for the seed companies . The greater the supply of these seed companies, the more the farmers become dependent, because the seeds result in a better yield.

further reading

  • Ellen Norten, Angela Lindner: Genetic engineering in everyday life - where we meet it and how we live with it . 106 pages. Egmont Vgs. 1997. ISBN 978-3-8025-1350-3
  • Klaus Wöhrmann, Jürgen Tomiuk and Andreas Sentker: Fruits of the future? Green genetic engineering . 228 pages. WILEY-VCH. 1st edition 1999. ISBN 978-3-527-29624-8 .

Web links

Individual evidence

  1. ↑ Directive 2001/18 / EC (PDF) (Release Directive ) Annex IA and B
  2. ↑ Varieties from protoplast fusion / CMS varieties. ( Memento from 7 February 2015 in the Internet Archive ) Information from Naturland specialist advice. January 15, 2013.
  3. ↑ IQSeeds database for cell fusion-free varieties. FiBL Projects GmbH. Research Institute for Organic Agriculture .
  4. ↑ FiBL : Updated positive list with cell fusion-free vegetable varieties published in: fibl.org, May 15, 2018, accessed on May 26, 2018.
  5. ↑ This is new in organic farming 2019. (PDF; 277 KB) In: shop. fibl.org . Bio Suisse , 2018, accessed on January 27, 2019 .