Resistance breeding
Under resistance breeding refers to various methods of plant breeding , which are intended to increase the resistance of plants to pests and diseases. The choice of the breeding method depends on the type of resistance .
Classic resistance breeding
The "classic" resistance breeding works with the various combination breeding methods, such as cross breeding and hybrid breeding.
Monogenic resistances (which are based on only one or a few genes) can be easily processed in breeding by crossing, with subsequent testing of the descendants for the presence of the relevant gene. Polygenic resistances (partial resistances) have hitherto been difficult to cultivate in terms of breeding and have therefore been used less often, but are much more permanent than monogenic resistances. Their breeding processing within the framework of cross breeding is classically associated with a high risk of loss of resistance in the course of the breeding process.
literature
- Becker: Plant Breeding. ISBN 3-8252-1744-2
Gene pyramidization
Gene pyramidization is a method of precision breeding in which marker- assisted different partial resistance genes , which together contribute quantitatively to a phenotypic trait , are brought together and thus to one of the above. polygenic resistance . In plant breeding , varieties can be obtained in a targeted manner, even without genetic engineering , which, through a combination of different resistance genes (different loci ), have a higher resistance to a pathogen than the starting varieties with their lower number of different resistance genes. At the same time, a pryramidized resistance of the cultivar cannot be overcome so easily by the development of resistance by the pathogen. Pyramidization in the more general sense means the combination of several genes from different genomes within one genome.
Genetic resistance breeding
In biotechnology , resistance breeding is understood to be the ability, for example, to modify a plant by cloning a certain gene in such a way that it is more resistant to external influences, such as e.g. B. herbicides or bacteria.
Fungus-resistant plants
Fungal diseases can lead to major crop damage. A historically important example of this is the potato rot ( Phytophthora infestans ), which led to considerable famine in Europe in the 19th century. By gene expression of the plant's own enzymes that are directed against the fungal cell wall, z. B. the fungus resistance of tobacco can be increased. Good results have also been achieved with the expression of ribosome- inactivating proteins (RIP).
Virus-resistant plants
Since viruses can cause significant crop losses, such as B. Potato virus 4 in the potato or the Rhizomania virus in the sugar beet , attempts are therefore made to intervene in the replication mechanism of the virus ( cross protection ) in the expression of virus proteins that are no longer functional in the plant . The expression of antiviral antibodies is also examined .
Insect Resistant Plants
The bacterium Bacillus thuringiensis forms a protein which is converted into a highly effective toxin in the insect intestine by proteolysis . However, the protein is not processed into toxin by plants and mammals. Therefore, one has the BT toxin as eating poison in numerous crops expressed . By codon optimization and use of strong, constitutive promoter (. As the 35S promoter of such cauliflower mosaic virus ) could be about gene expression rates increased 100-fold. Success has also been achieved with cloned protease inhibitors as food poison. A well-known application example is Bt maize , which is resistant to European corn borer .
Herbicide tolerant plants
Transgenic plants with herbicide tolerance are genetically modified in such a way that they either contain the herbicide-sensitive protein in large quantities, the herbicide either binds the herbicide less well or not at all at the site of action, or inactivates it through degradation. For example, the potato plant was made resistant to the inhibitor of glutamine synthase by cloning in a gene from the bacterium Streptomyces hygroscopicus . This inhibitor, phosphinothricin , is a component of various commercial herbicides and is mostly used as a broad spectrum herbicide with contact and partial systemic effects.
Individual evidence
- ^ Society for Plant Breeding (GPZ) .
- ↑ Gene pyramiding - A broad spectrum technique for developing durable stress resistance in crops , Biotechnology and Molecular Biology Review Vol. 5 (3), pp. 51-60, August 2010, ISSN 1538-2273
- ↑ see the verb pyramid in the English Wiktionary