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Breeding for disease resistance.pptx
- 1. Methods of Breedingfor disease Resistance Vishnupriya T.A. 2015-11-117
- 2. • Commonly followedbreeding methods are Selection Introduction Mutation Hybridization Soma clonal variation Genetic engineering
- 3. Selection • Selection resistantplants from commercial variety –cheapest and quickest method • This method has been very useful at past ,present-limited use • Eg:- Kufri red potato is a disease resistant selection from “Darjeeling red round • Eg:-Pusa swani bhindi –yellow mosaic resistant selection from collections in bihar
- 4. • Cotton varietyMCU 1 –selection from Co -4 – resistant to Black arm disease • Other examples • Resistance to curly top in sugar beet • Leaf spot and powdery mildew in alfalfa
- 5. Introduction • Resistant varietiesmay be introduced for cultivation into a new areas . • simple and quick means of obtaining resistance • Disadvantages • Sometimes introduced var may not perform well. • May become susceptible to concerned disease in a new envt. • They may be susceptible to other races of the concerned diseases in the new area
- 6. • Eg:- kenyawheat introduced into India were rust resistant , but susceptible to loose smut • Successful examples of introduction are 1. Ridley wheat introduced from Australia is rust resistant 2. Early variety of groundnut introduced from USA –resistant to tikka disease
- 7. Mutations • Resistance tosome disease may be obtained through mutations arising spontaneously or induced . • Spontaneous –at a low rate in nature • Induced –artificial , through chemical and physical agents • Mutagens- agents used physical –ionising -----alpha, beta ,fast neutrons , thermal neutrons, x rays, gamma rays _ non ionising -----ultra violet radiations chemical –alkaylating agents –EMS, MMS, sulphur mustard acridine dyes –ethium bromide Acridine yellow base analogues- 5- bromouracil
- 8. • Resistance tovictoria blight (Helminthosporium victoriae ) in oats was induced by irradiation with x-rays • Other examples are • Resistance to stripe rust and bunt in wheat. • Crown rust in oats • Mildew in barley • Rust in linseed
- 9. • Leaf spotand stem rot in peanut • Rust in soya bean • Bacterial leaf blight and bunt in rice • Powdery mildew in mungbean
- 10. Hybridization • Most commonmethod of breeding for disease resistance • 2 objectives for hybridization – • Transfer of disease resistance from a agronomically undesirable variety to a susceptible but other wise desirable(backcross) • Combining disease resistance and other desirable characters of one var with the superior characteristics of another variety(pedigree)
- 11. • Back crossmethod Useful in transferring genes for resistance from a var that is undesirable in agronomic characteristics to a susceptible var which is agronomicaly desirable and adapted Generaly 5-6 backcross are made . At the end of the cross ,progeny are selfed and resistant plants are selected The new variety is similar to the recurrent parent except for disease resistance .
- 12. Pedigree method • Thismethod is suited for breeding for horizontal or polygenic resistance • Majority of disease resistant commercial varieties have been developed through this method • Eg:- kalyan sona, Sonalika ,malviya 234, cotton variety like laxmi (resistant to red leaf blight)
- 13. Soma clonal variation •Somaclonal variation is the variation seen in plants that have been produced by plant tissue culture • Chromosomal rearrangements are an important source of this variation. • This is obtained in two ways • 1. plants regenerated from cultured cells are subjected to disease test and resistant plants are isolated • 2. cultured cells are selected for resistance to the toxin or culture filtrate produced by the pathogens • After that plants are regenerated from the selected cells
- 14. Callus Tissue Organogenesis Regenerated plantsHardening and Selfing Somaclonal Variants Steps involved in induction and selection of Somaclonal Variations
- 15. Advantages • Somaclonal variationleads to the creation of additional genetic variability. • Characteristics for which somaclonal mutants can be enriched during in vitro culture includes • resistance to disease pathotoxins • herbicides • high salt concentration • mineral toxicity and tolerance to environmental or chemical stress • increased production of secondary metabolites.