mutation breeding involves the incorporation of mutations in plant breeding techniques.

1. MUTATION BREEDING
Submitted to,
Mrs. Merin Alice George
Assistant professor
Dept of Botany
St Teresa’s college
Submitted by,
Silpa Selvaraj
Roll no : 13
I M.Sc. Botany
St Teresa’s college

2. OVERVIEW
 Historical account.
 Spontaneous and induced mutations.
 Effects of mutation.
 Mutagens.
 Procedure of mutation breeding.
 Gamma garden.
 Applications of mutation breeding.
 Merits and demerits of mutation breeding.
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3. HISTORICALACCOUNT
 The term mutation was coined by Hugo De Vries in1990.
 Mutations were known to occur in plants and animals much before this time.
 Short legged sheep – discovered by – farmer in the 18th century – it was used to produce a breed called
Ancon.
 Mutagenic action of X-rays – discovered by Muller – drosophila (1927).
 Mutagenic action of gamma rays and X-rays – by Stadler – barley and maize (1928).
 Muller was awarded Nobel prize (1946) for this work.
 Immediately after his discovery in 1927, mutation breeding programme were started in Sweden and
Germany.
 Mutation breeding attracted considerable attention during 1950s and 1960s, and several countries took up
research projects in mutation breeding.
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4. SPONTANEOUS AND INDUCED MUTATIONS
 Mutations that occur in natural populations, without any treatment by man are known as spontaneous mutations.
 The frequency of these mutations are generally one in 10 lakhs.
 Mutations may be artificially induced by treatment with physical or chemical mutagens. Such mutations are called
induced mutations.
 The utilization of induced mutations for crop improvement is called as mutation breeding.
 Induced mutations have great advantage over spontaneous mutations because they occur at a relatively higher
frequency so that it is practical to work with them.
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5. EFFECTS OF MUTATION
• Generally mutations have harmful effects on organisms.
• Usually they reduce the viability of the individuals that carry them.
• Based on their effect on viability , mutations are classified into 4 types;
 LETHAL MUTATIONS.
 SUBLETHAL MUTATIONS.
 SUBVITAL MUTATIONS.
 VITAL MUTATIONS.
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6.  LETHAL MUTATIONS
 Lethal mutations kill each and every individual that carry them in the appropriate genotype.
 Dominant lethals, therefore cannot be studied because they cannot survive even in the heterozygous state.
 Recessive lethals would kill the individuals that carry them in the homozygous state. Eg ; albina chlorophyll
mutations.
 SUBLETHAL MUTATIONS
 These mutations reduce viability.
 Do not kill all the individuals carrying them.
 Kills more than 50 percent of the individuals.
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7.  SUBVITAL MUTATIONS
 Reduces viability.
 Do not kill all the individuals carrying them.
 Kills much less than 50 percent of individuals carrying them.
 VITAL MUTATIONS
 Do not reduce viability.
 Can be used in crop improvement.
 Occur at a much lower frequency as compared to other three types.
Majority of mutations are lethal, sublethal
and subvital types. They have no value in
crop improvement
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8. MUTATIONS
(Based on magnitude)
MACROMUTATION MICROMUTATION
Produce large
phenotypic changes.
Produce small
phenotypic
changes
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9. MUTAGENS
A) PHYSICAL MUTAGENS
 Ionizing radiation
a) Particulate radiation. Eg; alpha rays, beta rays, fast neutrons, thermal neutrons etc.
b) Nonparticulate radiation. Eg; X-rays, beta rays etc.
 Nonionizing radiation. Eg; uv rays, visible light etc.
• Agents which induce mutations are called
mutagens.
• 2 types ; Physical mutagens and chemical
mutagens.
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10. B) CHEMICAL MUTAGENS
1. Alkylating agents : sulphur mustards, nitrogen mustards, epoxides, ethylene imines, sulphates, sulphonates, EMS
(ethyl methane sulfonate), MMS (methyl methane sulfonate) etc.
2. Acridine dyes : acriflavine, proflavine, acridine orange, acridine yellow, ethidium bromide etc.
3. Base analogues : 5-bromouracil, 5-chlorouracil etc.
4. Others : nitrous acid, hydroxyl amine, sodium azide etc.
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11.  CHOICE OF MUTAGENS
Selection of mutagens is based on the following criteria ;
 Effectiveness of mutagen : it is judged by observing the mutation frequency per exposure unit of mutagen.
 Efficiency of mutagen : here one works out mutation frequency in relation to frequency of undesirable effects like
chromosomal aberrations, sterility, lethality etc.
 Specificity of mutagen : here one looks at induction of a specific mutation by a specific mutagen.
Exposure of plant material to chemical mutagens can be modified by manipulating the concentration of mutagen
solution, duration of treatment, temperature etc.
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12. PHYSICAL MUTAGENS
 Beta rays
 High energy electrons produced by the decay of radioactive isotopes like 3 H, 32 P, 35 S etc.
 Little penetrating power as compared to X rays and gamma rays.
 This can be overcome by putting the beta radioisotopes in solution and administering them to the plant materials.
 Gamma rays
 Have shorter wavelength and possess more energy per photon than Xrays.
 The physical properties and biological effects of Xrays and gamma rays are similar, but they differ in the source of their
origin.
 X rays are produced by X ray tubes, while gamma rays are produced by radioactive decay of certain elements like
Radium, Cobalt 60, Cesium 137 etc.
 Both of them are highly penetrating and sparsely ionizing.
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13.  UV rays
 Low energy radiation ; non ionizing radiation.
 Low penetration ability.
 In genetic experiments on plants , its use is restricted to treating spores or pollen grains.
 X rays
 High energy radiations.
 Produced by x ray tubes.
 X rays of shorter wavelength = hard x rays, penetration greater than compared to x rays with longer
wavelength.
 X rays of longer wavelength = soft x rays , less penetrating.
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14. They are used in plant breeding methods due to following reasons ;
 Easy availability of x ray apparatus at many institutions.
 Easy to administer to seeds and other plant parts.
 Dose can be easily measured.
 X ray machines can be easily turned off , whereas isotope sources emit continuously.
 Neutrons
 They are uncharged particles that can highly penetrate biological tissues.
 Highly effective for the induction of mutation in plants.
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15. CHEMICAL MUTAGENS
 The mechanism of action of chemical mutagens varies to a great extent from one group of chemical mutagens to
another.
 The changes in DNA molecule produced by mutagens may be mutagenic or inactivating.
 Mutagenic changes do not prevent replication, produce changes in one or more nucleotides and do not produce
chromosomal aberrations.
 The alkylating agents have one, two or more reactive groups that react with DNA hence are called as mono, di or
polyfunctional respectively.
 Monofunctional alkylating agents – mutation breeding.
 Polyfunctional alkylating agents may causes chromosome breaks, chromosome mutations, gene mutations etc.
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16.  Azide
 Azide is commonly used as sodium or potassium azide.
 Induces high frequencies of chlorophyll and morphological mutations with negligible frequency of chromosomal
aberrations when used under acidic conditions.
 Inorganic azides – indirect mutagens – not mutagenic themselves. The mutagenic effects are produced by a
metabolite generated from them inside the cells.
 It has been reported to be mutagenic in several crop species. But in some plant species they are ineffective.
 It is the least dangerous, most efficient mutagen.
 Physiological effects of azides are weak, few chromosomal aberrations are induced and it delays germination and
growth.
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17. PROCEDURE FOR MUTATION BREEDING
 The utilization of induced mutation in crop improvement is called mutation breeding.
 Desirable mutations are induced in crop plants with the help of physical or chemical mutagens via mutagenesis.
 The variability generated through induced mutations are either released as new variety or used as parent in
hybridization programmes.
 Mutation breeding programme should be clearly planned and should be large enough with sufficient facilities to
permit an effective screening of large populations.
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18. 1.1 objectives of the programme
 The mutation breeding programme should have well defined and clear cut objectives.
 Procedure for the handling of treated population will depend mainly on whether an oligogenic or polygenic trait
is target for improvement.
1.2 Selection of the Variety for Mutagen treatment
 Generally the variety selected for mutagenesis should be the best variety available in the crops.
 The seeds used for treatment should be as pure as possible.
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19. 1.3 Part of the plant to be treated
 Seeds, pollen grains or vegetative propagules or even complete plants may be used for mutagenesis.
 In sexually propagated crops, seeds are the most commonly used plant parts.
 Pollen grains may be used, but they are infrequently used because it is difficult to collect large quantities of
pollen grains in most of the crops, pollen survival is relatively short.
 Pollen grains are the only plant part that can be successfully treated with UV radiation.
 Whole plants are irradiated during the flowering stage so that it is equivalent to the irradiation of pollen grains
and egg cells. However the treatment of whole plants require special facilities (Gamma garden) and is possible in
few places only.
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20. 1.4 Dose of the mutagen
 Mutagen treatments reduce germination, growth rate, vigour and fertility.
 There is considerable killing of plants during various stage of development after mutagen treatment; thus survival is
reduced considerably.
 Mutagens induces high frequency of chromosomal changes and mitotic, meiotic irregularities.
 The damages increases with the dose of the mutagen.
 An optimum dose is the one which produces the maximum frequency of mutations and minimum killings.
 A dose close to LD 50 is the optimum. LD 50 is that dose of the mutagen which would kill 50% of the treated individuals.
 LD 50 varies with the crop species and with the mutagen used. A preliminary experiment is conducted to determine
suitable mutagen dose.
 Over dose kill too many treated individuals, under dose produce few mutations.
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21. 1.5 Giving mutagen treatment
 The selected plant part is exposed to desired mutagen dose.
 M1 generation is produced directly from the mutagen treated plant parts.
 M2, M3 and M4 are the subsequent generations derived from M1, M2 and M3.
 In case of chemical mutagens, seeds are pre-soaked for few hours to initiated metabolic activities, exposed to
desired mutagen and then washed in running tap water to remove the mutagen present in them.
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22. MUTATION BREEDING FOR OLIGOGENIC TRAIT
 First year (M 1)
• Several hundred seeds are treated with a mutagen and are space planted.
• The number of treated seeds is so adjusted as to give rise to ~500 fertile M 1 plants at the harvest.
• Care should be given to prevent outcrossing.
• Seeds from the M 1 plants are harvested separately to raise M 2 progeny.
 Second year (M 2 )
• About 2000 progeny rows are grown.
• Careful observations are made on the M 2 rows.
• All the plants suspected of containing new mutations are harvested separately to raise individual plant progenies
in M 3 .
• If the mutant is distinct, it is selected for multiplication and testing. But most mutations – useless – crop
improvement. Only 1-3 % of M 2 rows are expected to have beneficial mutations.
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23.  Third year (M 3)
• Progeny rows from selected individual plants are grown in M 3.
• Poor and inferior mutant rows are eliminated.
• If the mutant progenies are homogenous, two or more M 3 progenies containing the same mutations are harvested
in bulk.
• If the progenies are heterozygous, individual plants are harvested.
• Preliminary yield trial is conducted in M 4 using the mutant M 3 rows.
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24.  Fourth year (M 4)
• Preliminary yield trial is conducted using a suitable check.
• Superior mutant lines are selected for replicated multilocation trials.
 Fifth year-seventh year (M 5 –M 7 )
• Repeated yield trials are conducted at several locations.
• The outstanding line is released as a new variety.
• Seeds are then multiplied and distributed among farmers.
• The low yielding mutant lines are collected and used in hybridization programmes.
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25. MUTATION BREEDING FOR POLYGENIC TRAITS
 M1 – M2
 M1 and M2 are grown in the same way as in the case of oligogenic traits.
 In M2, vigorous, fertile and normal looking plants that do not exhibit a mutant phenotype are selected and their
seeds are harvested separately to raise individual plant progeny rows in M3.
 M3
 Progeny rows from individual selected plants are grown.
 Careful observations are made on M3 rows for small deviations in phenotype from the parent variety.
 Inferior rows are discarded.
 Homogenous progenies are harvested in bulk.
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26.  M4
 Seeds from homogenous M3 rows are planted in a preliminary yield trial with a suitable check.
 Progenies showing segregation may be subjected to selection only if they are promising.
 Superior progenies are selected and harvested in bulk for preliminary yield tests in m5.
 M5- M8
 Multilocation trials are conducted .
 Outstanding progenies are released as new varieties.
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27. GAMMA GARDEN
 Gamma garden or atomic garden is a concept popularized after the world war 2 for the peaceful use of atomic
energy for the crop improvement.
 They are a type of induced mutation breeding where gamma rays from cobalt 60 or caesium 137 are used to induce
desirable mutations in crop plants.
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28.  First gamma garden – Long Island, New York.
 First gamma garden in India – Bose Research Institute, Kolkata.
 It is an area subjected to gamma irradiation.
 Giant structures – enclosed by thick, high wall to protect the plants and animals outside.
 The source of radiation is located at the center of the gamma garden.
 The intensity of radiation decreases as one moves away from the source of radiation.
 The area around the radiation source is divided into number of concentric circles representing varying
intensities of radiation.
 Plants to be irradiated are arranged as concentric circles around the radiation source.
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29.  The radially arranged plants in gamma garden can be grouped into three sectors.
1. Sector 1
 Plants nearest to the radiation source.
 The plants in sector 1 usually die immediately due to the high dose of radiation.
 They are not used in further experiments.
2. Sector 2
 Include plants located next to sector 1.
 They develop severe tumors, malformations and other abnormalities.
 They are not used in further experiments.
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30. 3. Sector 3
 Includes plants located next to sector 2.
 They are the actual plants of interest in gamma gardens.
 They may have random mutations not severe enough to damage the crop plant.
 The variations in sector 3 are used in further breeding experiments.
 They can be used in hybridization or can be directly released as a variety.
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31. APPLICATIONS OF MUTATION BREEDING
 Mutation breeding has been used for improving both oligogenic as well as polygenic characters.
 It improves morphological and physiological characters like disease resistance and yielding ability of cultivated
crops.
 Useful in improving the specific characteristics of a well adapted high yielding variety.
 Mutagenesis has been successfully used to improve various quantitative characters including yield.
 F1 hybrids obtained from intervarietal crosses may be treated with mutagen to increase genetic variability by
inducing mutation.
 It is effective in disseminating an undesirable character from a crop variety.
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32. MERITS
 Compared to other methods, mutation breeding is a cheap and rapid method for developing new varieties with
entirely new characters.
 It is more effective for the improvement of monogenic characters like disease resistance, than for polygenic
characters.
 Mutation breeding is simple, quick and most effective to induce a new character in vegetatively propagated crops.
 Mutation breeding often breaks undesirable gene linkage.
 Mutation breeding may produce haploids from unfertilized eggs.
 Mutation breeding may produce transitory sexuality in apomictics.
 Mutation breeding may produce distant hybrids with translocation.
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33. DEMERITS
 The frequency of desirable mutations is very low, about 0.1 % of total mutations.
 The breeder has to screen a large population to select a desirable mutation.
 Desirable mutations are commonly associated with undesirable side effects.
 Mutations often produce pleiotropic effects.
 There may be problems in registration of mutant variety in many parts.
 Most of the mutations are recessive and their side effects are not expressed due to the dominance of its allelic
counterpart.
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34. REFERENCES
1. Chopra, V.L. (1968). Plant breeding: Theory and practice. New Delhi. Oxford and IBH
Publishing Company.
2. Frey, K.J. (1977). Plant breeding. The IOWA State University Press.
3. Ram, M. (2014). Plant breeding methods. New Delhi.
4. Singh, B.D. (1993). Plant breeding: Principles and methods. New Delhi. Kalyani Publishers.
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35. THANK YOU
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