BREEDING METHODS FOR DISEASE RESISTANCE.pptx

Plant breeding for disease resistance is a strategy to reduce crop losses caused by disease. Plants have an innate immune system that allows them to recognize pathogens and provide resistance. However, breeding for long-lasting resistance often involves combining multiple resistance genes

1. BREEDING METHODS FOR DISEASE RESISTANCE RASHMI M G 1 st year MSc. Botany Maharani’s science college for women Mysore

2. Introduction Disease is an abnormal condition in an organism/ plant produced by an organism or an environmental factors. Plant disease may be defined as the series of invisible and visible responses of plant cells and tissues to a pathogenic microorganism/ an environmental factor that result in adverse changes in form, function or integrity of plants and may lead to partial impairment/ death of the plant or its parts.

3. Disease development

4. Losses due to diseases Killing of plants. Killing of branches. General stunting. Damage to the leaf tissues. Damage to the reproductive organs including fruits and seeds. Can be lethal. Economic losses.

5. Breeding methods for disease resistance Sources of disease resistance. Methods of breeding for disease resistance. Advantages and disadvantages of breeding methods.

6. Sources of disease resistance

7. Sources of disease resistance A known variety - disease reactions of most of the cultivated varieties are documented, and a breeder may find the resistance be needs in a cultivated variety. ex. Resistance plants were isolated from commercial varieties in the cases of cabbage yellow disease (causal organism- Fusarium sp.) these plants provided the basis for new resistant varieties of these crops.

8. Sources of disease resistance 2. Germplasm conservation - when a resistance to new diseases/ new pathogen of a disease is not known in a cultivated variety. ex. Resistance to net-blotch in barley.

9. Sources of disease resistance 3. Related species - transfer of resistance genes from related species through interspecific hybridization. ex. Genes fro resistance to stem and leaf rusts of wheat. LR9, LR19, LR22a, LR24, LR25, LR26 for leaf rust. SR21, SR24, SR25, SR26, SR27, SR31, SR32 for stem rusts in wheat.

10. Sources of disease resistance 4. Mutations -resistance to some diseases may be obtained through spontaneous/ induced mutations. It makes use of irradiation like X-rays or thermal neutrons ex. Resistance to Victoria blight ( Cochliobolus victoriae)

11. Sources of disease resistance 5. Somaclonal varieties - genetic variation occurs in plant cells cultured in vitro, in plants regenerated from such cells and in the progeny of the plants. somaclonal variants resistant to various diseases have been isolated in many crops and some of these have been released as varieties. ex. Ono variety (in a somaclone of variety Pindar)

12. Sources of disease resistance 6. Unrelated organisms - it utilizes genes from other organisms to produce disease resistance in plants. Ex. Coat protein gene of a pathogenic virus for virus resistance, or from other plants. Ex. Genes for novel phytoalexins.

13. Methods of breeding for disease resistance Selection - selection of disease resistant plants from a commercial variety is the cheapest and the quickest method of developing a resistant variety. Ex. Kufri red potato is a disease resistant selection from Darjeeling Red round. 2. Introduction - resistant varieties may be introduced for cultivation in a new area. This offers relatively simple and quick means of obtaining resistant varieties. ex. Early varieties of groundnut introduced from USA were resistant to leaf spot/ tikka disease.

14. Methods of breeding for disease resistance 3. Hybridization - most common method of breeding for disease resistance. It serves the following 2 chief purposes, - transfer of disease resistance from a n agronomically undesirable variety. (by backcross method) - combining disease resistance and some other desirable characters of one variety with the superior characteristics of another variety (by pedigree method)

15. Methods of breeding for disease resistance 4. Genetic engineering - in this approach genes expected to confer disease resistance is isolated, cloned and transferred into the crop. ex. Virus coat protein gene, DNA copy of viral satellite RNA, defective viral genome etc.

16. Conclusion Plant breeding for disease resistance is a strategy to reduce crop losses caused by disease. Plants have an innate immune system that allows them to recognize pathogens and provide resistance. However, breeding for long-lasting resistance often involves combining multiple resistance genes

17. References PLANT BREEDING-PRINCIPLES &METHODS, B D Singh, Kalyani publications, page no. 444-484 https://www.biologydiscussion.com/ https://www.google.com/plant /