Mutation breeding

For B.Pharm, 4th Sem

1. Mutation Breeding in Plants

2. Introduction The word mutation is derived from Latin word “ mutatus ” meaning “changed” In biology, a mutation is the permanent alteration of the nucleotide sequence of the genome of an organism, virus or extra-chromosomal DNA or other genetic element. Refers to sudden heritable change in the phenotype of an individual. Mutation breeding: referred to as variation breeding is the process of exposing plants or seeds to chemical or radiation in order to generate mutants with desirable traits to be bred with other cultivars ( plant varieties) Plants/seeds created using mutagenesis are called mutagenic plants or mutagenic seeds.

3. Mutant: A mutant is an organism or a new genetic characters arising or resulting from mutation which is an alteration of the DNA sequence of a gene or chromosome of an organism. From 1930 to 2014 more than 3200 mutagenic plant varieties were released & still counting. From direct mutation 70% and from their progeny 30% Natural occurrence of genetic mutation is integral to the process of evolution Mutation occurs in two ways : (1) By alteration in nuclear DNA (point mutations) (2) By change in cytoplasmic DNA ( cytoplasmic mutation )

4. History 1927 – First proof of induced mutations in plants; radium ray treatment of Datura stramonium ( Gager and Blakeslee). 1927 – H. J. Muller working with Drosphila provides proof of mutation induction by X-rays, Muller champions induced mutation for animal and plant breeding and opens a new era in genetics and breeding. 1928, Stadler publishes the first results of mutation induction in crop plants, barley, maize, wheat and oat, etc.

5. 1936, The first induced mutant variety is released, tobacco variety-‘ Chlorina ’ using X-rays in Indonesia. 1942, First report of induced disease resistance in a crop plant; X-ray induced mildew resistance in barley ( Freisleben and Lein ). 1944/46 First reports of chemical induced mutation ( Auerbach and Robson).

6. TYPES OF MUTATION

7. TYPES OF MUTATION Spontaneous mutations : Mutation occur in natural populations. Natural exposure of a plant to certain environmental factors, such as ultraviolet light and chemical carcinogens (e.g., Aflatoxin B1 ). A common  cause of spontaneous   point   mutations  is the de- amination of cytosine to uracil in the DNA double helix. Induced mutations : Mutation may be artificially induced by various mutagenic agents. Induced mutations are of two types: i ) Macro-mutations : Mutation with distinct morphological changes in the phenotype. ii) Micro-mutations : Mutations with invisible phenotypic changes.

8. De- amination of cytosine to uracil

9. MUTATION BREEDING Inducing desirable mutations and exploiting them for crop improvement. It is commonly used in self pollinated crops and used to produce traits in crops such as larger seeds, new colour, greater yields, etc. Important steps to know before mutation breeding are: 1.Selection of variety for mutation breeding, It should be the best variety available in crop and Seed should be pure 2.Part of the plant to be treated 3.Dose of the mutagen (LD50): Mutagens generally induce a high frequency of chromosomal changes and meiotic and mitotic irregularities, Optimum mutagen dose is one, which produces maximum frequency of mutations and causes the minimum killing.

10. MUTAGENS Mutagen : Physical or chemical agent which greatly enhance the frequency of mutation. Types of mutagens: A. Physical mutagens: 1.Ionising radiation: (a)Particulate radiations: alpha-rays, beta-rays, fast neutrons and thermal neutrons. (b) Non-particulate radiations: x-rays and Gamma rays. 2.Non-ionising radiation : ultraviolet radiation.

11. B. Chemical mutagens: 1.Alkylating agents: EMS `(ethyl methane sulphonate ), methyl methane sulphonate (MMS),sulphur mustard, nitrogen mustard 2.Acridine dyes: Proflavin , acridine orange, acridine yellow and ethidium bromide. 3.Base Analogues: 5 Bromo uracil , 5 chloro-uracil . 4.Other mutagens: Nitrous Acid, Sodium Azide .

12. BREEDING PROCEDURE

13. Screening/selection Mainly three types screening/selection techniques are used in M2 and subsequent generation. 1. Visual: most effective and efficient method for identifying mutant phenotypes . 2. Mechanical/Physical: Very efficient for seed size, shape, weight, density, etc., using appropriate sieving machinery. 3. Other methods: Low alkaloid content mutants can be selected using colorimetric tests ( method of determining the concentration of a chemical element or chemical compound in a solution with the aid of a colour reagent) , chromatographic or electrophoresis techniques may be used to select isolate protein variants

14. Advantages of mutation breeding Mutation breeding is a cheap and rapid method of developing new varieties. Induced mutagens are used for the induction of CMS ( Cytoplasmic male sterility) . Ethidium bromide (EB) has been used for induction of CMS in barley. Mutation breeding is more effective for the improvement of oligogenic characters (a trait that is influenced by more than one gene). Mutation breeding is the simple, quick and the best way when a new character is to be induced.

15. Disadvantages The process is generally random and unpredictable. Useful mutants are rare and predominantly recessive. Mutants can have strong negative pleiotropic effects on other traits. Health risks: handling, chemical mutagens; radiations, fast neutrons treatments. Most mutants are of no use to breeding even if a large number of mutants can be produced. Field trialling and germplasm storage can be expensive and require a lot of space and careful management if large mutant populations are handled.

16. The primary research centres and institutes in India that participated in the development and release of various mutants Indian Agricultural Research Institute (IARI)-- New Delhi Bhabha Atomic Research Centre--Mumbai Tamil Nadu Agricultural University--TN and National Botanical Research Institute-- Lucknow , UP

17. Achievements of mutation breeding Higher yield Barley (DL 253), Pea (Hans), Groundnut (Co 2, TG 17). Short stature Barley (RDB 1),Rice ( Prabhavati ). Earliness Rice (IIT 48,IIT 60,Indira,Padmini) Stress resistance, Salt tolerance in Rice (Mohan) water logging tolerance in jute ( Padma ) Bold seed size Groundnut (PB 1,PB 2,Vikram) and Rice ( Jagannath ).