MUTATION BREEDING IN CROP IMPROVEMENT

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By: jashok (37 month(s) ago)

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MUTATION BREEDING IN CROP IMPROVEMENT AK Chhabra Department of GENETICS AND Plant Breeding CCSHAU, Hisar Copyright of original figures taken from other sources lie with the original developer. This is not for commercial purpose but for educational use only

Introduction : 

Introduction Mutation is a sudden heritable change in a characteristic of an organism . Gene/Point mutation :- Mutation produced by changes in base sequence of genes . Chromosomal mutation :- Mutation may be produced by changes in chromosome structure or even in chromosome number.

Historical Account : 

Historical Account Hugo de Vries: 1900. introduced the term “Mutation”. Mutants were observed before this: e.g., short legged sheep was discovered by an English Farmer in 18th century. This sheep was used to develop a breed-c/a Ancon. Muller-discovered the action of X-rays on Drosophilla and Stadler discovered the effect of gamma-rays in barley. Mutation Breeding Programme was started in Sweeden, USSR and Germany in 1927 after the discovery by Muller. Hugo de Vries Short-legged sheep Muller with his wife Stadler

Transitions and Transversions : 

Transitions and Transversions PURINES PURINE PYRAMIDINES PYRAMIDINES A G C T Transitions Transversions Texas A&M Aggies Shirts AGGIES ARE PURE

Point and Cytoplasmic Mutations : 

Point and Cytoplasmic Mutations Alteration in the nuclear DNA Alteration in the cytoplasmic DNA CMS

Types of mutations : 

Types of mutations Spontaneous and Induced mutations Macro and Micro mutations c/a Oligo mutations / Quality Mutations Phenotypic effect is quite clear c/a polygenic mutations, are for quantitative traits, are of economic importance, phenotypic effects are invisible, need large populations to score mutations and special statistical analysis is required to detect their effect (biometrical techniques) Natural mutation Artificial mutations

Effects Of Mutation : 

Effects Of Mutation Lethal :- They kill each & every individual that carry them in appropriate genotype . Dominant lethal : It can’t survive. Recessive lethal : kill in homozygous state. Sub Lethal & Sub Vital :- Both mutation reduce viability but don’t kill all the individual carrying them in appropriate genotype. Sub Lethal : Kill more than 50%. Sub Vital : Kill less than 50%. Vital :- a) Don’t reduce the viability. b) Crop improvement can utilize only such mutations.

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Lethal , Sub lethal mutations have no value in crop improvement.

Mutation breeding : 

Mutation breeding The genetic improvement of crop plants for various economic traits through the use of induced mutations is referred to as mutation breeding. Used in S.P. and clonally propagated crops. Wheat Sugarcane

Mutation breeding is successful when…… : 

Mutation breeding is successful when…… Desired variability exhausts in cultivated species and germplasm. When a desirable variety has an oligogenic genetic defect. There is tight linkage between desirable and undesirable traits. Only one or two characters are to be improved in a fruit crop without changing its taste. Crop does not have sexuality, thus lacks variability. The generation cycle is very long, such as plantation crops, fruit trees….there mutation breeding is the shortcut way for genetic improvement. In ornamental plants Mutant Dog Rose Flower Mutant yellow Rose Red Rose

Mutation breeding is successful when…… : 

Mutation breeding is successful when…… A particular reaction is to be blocked e.g., in opium the synthesis of morphine takes place in stepwise manner. If the reaction is stopped at bane level, it will block the synthesis of morphine without affecting the conversion process of the bane into useful pharmaceutical products. A B C D E H I J K Enzyme1 Enzyme 2 Enzyme 4 Enzyme 5 Enzyme6 Enzyme 7 Enzyme 8 Enzyme 3

Mutation breeding is successful when…… : 

Mutation breeding is successful when…… A particular reaction is to be blocked e.g., in opium the synthesis of morphine takes place in stepwise manner. If the reaction is stopped at bane level, it will block the synthesis of morphine without affecting the conversion process of the bane into useful pharmaceutical products. A B H I J K Enzyme1 Enzyme6 Enzyme 7 Enzyme 8 Enzyme 3 Mutates

Mutagens : 

Mutagens

Procedure for mutation breeding : 

Procedure for mutation breeding Mutagenesis :- Treating a biological material with a mutagen in order to induce mutation. Irradiation :- Exposure of biological material to one of the radiation(X-rays, gamma rays etc.).

Selection of the variety for mutagen treatment : 

Selection of the variety for mutagen treatment Generally the variety selected for mutagenesis should be the best variety available in the crop. Note : In certain situations, it may be desirable to isolate variants in varieties other than the best one, e.g., Dwarf & semi dwarf mutants would have to be isolated from tall varieties in cereal crops (wheat, rice etc.)

Part of the plant to be treated : 

Part of the plant to be treated Seeds, pollen grains, buds/cuttings or complete plant can be used for mutagenesis. It depends on whether the crop is sexually or asexually propagated & type of mutagen to be used. Sexually propagated crops : Seeds are commonly used because seed can tolerate extreme environmental conditions.

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They are difficult to collect in large quantities . Hand pollination(with treated pollens) is rather difficult. Survival percentage of pollens is relatively low. Note:- Pollen grains are the only plant part which can be treated with ultra violet rays. Clonal crops : Buds/cuttings are used for mutagenesis. Pollen grains are also infrequently used because :-

Dose and duration of the mutagen : 

Dose and duration of the mutagen The usefulness of a mutagen and its efficiency depends on the mutagenic agent employed as well as on specific characteristics of the biological system to be treated. An optimum dose is the one which produce the maximum frequency of mutation and causes minimum killing. LD50 dose should be optimum.

Description of generations : 

Description of generations M1 Plants obtained from treated seeds/cuttings or from seeds obtained after pollination with treated pollens are called M1 plants Treated seed/buds/cuttings Pollination with treated pollen M1 Plants

Description of generations : 

Description of generations M1 Plants obtained from treated seeds/cuttings or from seeds obtained after pollination with treated pollens are called M1 plants M1 Plants Large no. of plants are grown Grown in wider spacing. Dominant mutations are recorded if any (generally mutations are recessive and do not express in M1) Chlorophyll sectors and fertility is recorded. M1 plants are selfed and their seed is harvested separately.

Procedure : 

Procedure M2-----Seed obtained from M1 is sown in wide spacing Selected mutants are selfed. Oligogenic mutations are detected in M2 and are harvested separately. M3-----M3 progeny is raised from selected M2 and evaluated for homozygosity. Selected homozygous M3 progenies are bulked together to conduct yield trials in M4. M4-----M4 progeny are raised in replicated trials using local check for comparison. M5-M9----Selected lines are tested in multiplication coordinated trials

Procedure for Vegetative propagated crops : 

Procedure for Vegetative propagated crops In Veg. Prop. Crops mutations are expressed in the form of chimeras. The chimera refers to genetically different tissue in an individual. The individual has one type of tissue in one part and another type of tissue in another part.

Procedure for Vegetative propagated crops : 

Procedure for Vegetative propagated crops In apical buds, axillary buds and adventitious buds, there are two functional layers, outer layer and inner layer. When the changes occur in entire inner or outer layer, it is also known as Periclinal Chimera and when only a part of inner or outer layer is altered, it is called Sectorial Chimera.

Chimera ? : 

Chimera ? Vegetative mutations are expressed in the form of chimeras. Periclinal chimera (whole of inner and outer layer) Sectorial chimera(part of inner/outer layer) Seed propagated crop-inner layer important…seed formation Chimera - a plant or plant part composed of genetically different layers

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AA AA AA L1 L2 L3 Shoot-Tip Meristem AA AA AA AA AA AA AA AA AA Aa L1 L2 L3 L1 L2 L3 L1 L2 L3 Sectorial and Periclinal Chimeras produced by mutagenesis. The Mutant allele (a) is recessive. Produces Epidermis Produces leaf mesophyll and gametes. Produces rest of plant body When whole of the L1, L2 or L3 is affected, it is called PERICLINAL CHIMERA When part/segment of the L1, L2 or L3 is affected, it is called SECTORIAL CHIMERA Three functional layers Shoot-Tip Meristem Shoot-Tip Meristem Shoot-Tip Meristem AA AA AA AA L1 L2 L3 Shoot-Tip Meristem Chimera ?

Slide 26: 

AA AA AA L1 L2 L3 Shoot-Tip Meristem L1 L2 L3 L1 L2 L3 L1 L2 L3 L1 L2 L3 Sectorial and Periclinal Chimeras produced by mutagenesis. The Mutant allele (a) is recessive. Produces Epidermis Produces leaf mesophyll and gametes. Produces rest of plant body When whole of the L1, L2 or L3 is affected, it is called PERICLINAL CHIMERA When part/segment of the L1, L2 or L3 is affected, it is called SECTORIAL CHIMERA Three functional layers Chimera ?

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Chimera - a plant or plant part composed of genetically different layers Chimera ? The most common example is a "variegated" plant where different regions of the leaf are yellow or white due to the lack of chlorophyll synthesis, i.e. these are chlorophyll mutants. However, there are many kinds of chimeras. Thornless blackberries are chimeras where the L-I epidermis lacks the ability to produce thorns. Some fruits have sweet and sour regions of flesh, which may be a chimera.

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Alöe mitriformis variegata Variegated Geranium

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Acer platanoides "Drummondii"   (Family: Aceraceae) Common name: Variegated Norway maple

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Arum italicum chimera variegated flower of Mirabilis sp. Amaranthus Tricolor Perfecta

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Mericlinal Chimera A mutation occurs in one layer and along the side of the apex. Due to its position, the cell division products of those mutated cells occur as a layer on only one side of the plant. In other words, only a section of one of the layers is mutated. Mericlinal chimeras are not stable.   Periclinal Chimera A mutation occurs in one (or more) layer at the top of the apex. Due to its position, the cell division products of the mutated cells spread and cover the entire layer of the apex. In other words, the entire layer is mutated. Periclinal chimeras are stable to very stable, and comprise the most common type chimeras in horticulture.   Sectorial Chimera A mutation occurs in multiple layers at the top of the apex. Due to its position, the cell division products of the mutated cells give rise to a section of mutated cells. In other words, an entire section of the plant is mutated. Sectorial chimeras are stable to very stable, and comprise the most common type chimeras in horticulture. Chimera ?

Slide 37: 

Chimera ? Layering of Periclinal Chimeras A periclinal chimera will have the mutated region(s) restricted to the layer(s) which was mutated in the apical meristem. If a plant is variegated because it is a periclinal chimera, the pattern of variegation should have a geometrical organization similar to the pattern . If the pattern is more of a mosaic, spots, blotches, or lateral stripping, it is probably not a chimera, but rather genetically determined. Or, the plant may be one of the other chimeral types, i.e. sectorial or mericlinal chimeras. A chimeral pattern can also occur in flower petals, such as multi-colored African Violets or petunia flowers.

Slide 38: 

Chimera ? Periclinal Chimeras Check LI, LII and LIII layers

Slide 39: 

Chimera - a plant or plant part composed of genetically different layers Chimera ? Stock Image of Red Ornamental Variegated Pineapple Fruit

Giving mutagen treatment : 

Giving mutagen treatment The plant part is exposed to the desired mutagen dose. In irradiation the plant parts are immediately planted to raise M1 plants from them. In case of chemical mutagens seeds are usually soaked for few hours to initiate metabolic activities. Then they are washed under running tap water. After this they are planted in the field to raise M1 generation.

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Mutation treatment to pollen (UV rays) Pollination F1 seed F1 plant Pollination M1 seed M1 plant F2 seed M2 seed Mutation treatment to SEED (rays/chemical) M1 seed M1 plant M2 seed M2 plant Shows variation for dominant mutations only Shows variation like F2 Shows variation for dominant mutations only Shows NO variation

Handling of mutagenic population : 

Handling of mutagenic population Treatment of seeds & vegetative propagules commonly produce chimeras. Shoot tip meristem has three layers :- L1 :- Give rise to epidermis. L2 :- Part of leaf mesophyll & gametes. L3 :- Yield the rest of plant. Periclinal chimera :- When the whole of L1 , L2 or L3 layer is affected. Sectorial chimera :- When only a part of L1 , L2 or L3 layer is affected .

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In sexually reproducing species L2 chimera will be transmitted to the next generation. In sexually reproducing crops mutation breeding utilize both recessive & dominant mutations.

Application of mutation breeding : 

Application of mutation breeding Induction of desirable mutant alleles which may not be present in the germplasm available to the breeder. In improving specific characteristics of well adapted high yielding variety . Mutagenesis has been successfully used to improve various quantitative characters including yield.

Limitations : 

Limitations The frequency of desirable mutants is very low. Desirable mutations are commonly associated with undesirable side effects. There may be problems in the registrations of a mutant variety. Mutations in quantitative traits are usually in the direction away from the selection history of the parent variety. Most of the mutations are recessive.

List of some varieties developed in india through mutation breeding : 

List of some varieties developed in india through mutation breeding

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THANKS