Breeding for disease resistance.pptx

Include different types of breeding for disease resistance in plants

1. Methods of Breeding for disease Resistance Vishnupriya T.A. 2015-11-117

2. Commonly followed breeding methods are Selection Introduction Mutation Hybridization Soma clonal variation Genetic engineering

3. Selection Selection resistant plants from commercial variety –cheapest and quickest method This method has been very useful at past ,present-limited use Eg :- K ufri 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 variety MCU 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 varieties may be introduced for cultivation into a new areas . simple and quick means of obtaining resistance Disadvantages Sometimes introduced var may not perform wel l. 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 :- kenya wheat introduced into India were rust resistant , but susceptible to loose smut Successful examples of introduction are Ridley wheat introduced from Australia is rust resistant Early variety of groundnut introduced from USA –resistant to tikka disease

7. Mutations Resistance to some 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 to victoria 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 spot and stem rot in peanut Rust in soya bean Bacterial leaf blight and bunt in rice Powdery mildew in mungbean

10. Hybridization Most common method of breeding for disease resistance 2 objectives for hybridization – T ransfer 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 cross method 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 This method 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 plants Hardening and Selfing Somaclonal Variants Steps involved in induction and selection of Somaclonal Variations

15. Advantages Somaclonal variation leads 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.