Mutation breeding-methods
and uses
Dr. Prabhat Kr. Singh
Assistant Professor,
Department of Genetics and Plant Breeding
MSSSoA, CUTM, Paralakhemundi, Odisha, India
Definitions
❖ In broad sense mutation is sudden
heritable change in genetic material,
that is not due to recombination and
segregation.
❖ It includes chromosomal aberration
as well as change in individual gene
or even a base pair.
❖ In molecular biology and genetics,
mutations are changes in individual
Altered gene.
protein
❖ Mutagen: Any substance that can
bring about the mutation.
❖ Mutant: The organism exhibiting a
novel phenotype as a result of
mutation.
Historical Background
❖ Derived from the latin word ‘MUTARE’ means to change
❖ Term mutation introduced by Hugo de Veris (1900) while
studying evening primerose (Oenothera lamarckiana).
❖ But the earliest record of mutations dates to 1791 when Seth
Wright noticed a male lamb with unusually short legs in his flock
of sheep.
❖ Systematic studies on mutation begain in 1910 with the discovery
of white eye mutants of Drosophola by T. H. Morgan.
❖ Mutagenic action of X-rays discovered by H. J. mulier (1927)
in Drosophola.
❖ Stadler (1929) described the mutagenic effect of X-rays in
barley.
❖ Mutagenic effect of mustard gas and some other chemical
compound discovered by Auerbach and Robson in 1946 in
Drosophila.
There are three types of mutations based on genetic
basis of heritable change :
1. Gene mutations: These are produced by change in
the base sequence of genes. The change may be due
to base substitutions, deletion or addition.
2. Chromosomal mutation: These arise due to change in
chromosome number that may leads to polyploidy or
aneuploidy or change in chromosome structure that
result in deletions duplication, inversion and
translocation.
3. Cytoplasmic or plasmagene mutation: These are due
to change in the base sequence of plasma genes. The
plasma genes are present in mitochondria/chloroplast.
Here the mutant character occurs in buds or somatic
tissues which are used for propagation in clonal crops.
Classification of mutations
Based on origin, the mutations are classified as spontaneous
and induced mutations.
1. Spontaneous mutations: Mutations occur in natural populations
at a low rate (10-6) but different genes may show different
mutation rates. For example : in maize R-locus mutates at the
frequency of 4.92 x 10-4 i.e. (1 in 20000 population), whereas
Su locus at 2.4 x 10-6 (1 in 25 lakhs). The Wx locus considered
to be highly stable. The difference in mutation rate may be due
to (a) Genetic back ground i.e. presence of mutator genes (b)
Genes them selves (c) Environment.
2. Induced mutation: Mutations may be artificially induced by
treatment with certain physical or chemical agents. Induced
mutations are comparable to spontaneous mutations in their
effects and in the variability they produce. Induced mutation
occur at a relatively higher frequency so that it is practical to
work with them.
Based on magnitude of phenotypic effects
mutation as classified as
1. Macro mutations: Oligogenic Mutation – Large
phenotypic effect and recognizable on individual plant
basis and can be seen easily in M2 generations – E.g.
Ancon breed in sheep, pod maize to cob maize
2. Micro mutations: Polygenic mutations – Small
phenotypic effect which can not be recognized on
individual plant basis but can be recognize only in a
group of plants. Selection should be done in M3 or
later generations.
Characteristics of mutation
1) Mutations are mostly recessive and very rarely dominant
e.g. epiloia in human, Notch wing in Drosophila etc.
2) Most mutations have harmful effects and very few (less
than 0.1 %) are beneficial.
3) Mutations are random event in term of time of their
occurrence and the gene in which they occur.
4) If gene mutations are not lethal, the mutant individuals
may survive. However, chromosomal mutations are
generally lethal and such mutants do not survive.
5) If mutation occur at both loci simultaneously, the
mutants can be identified in M1 generation. However, if
it is restricted to one locus only, (dominant to recessive)
the effect can be seen only in M2 generation.
6) Many of the mutants show sterility.
7) Mutations are random i.e. they can occur in any tissue
or cell of an organism. However, some genes show
higher mutation rate than others.
8) Mutations are recurrent i.e. the same mutation may
occur again and again.
9) Induced mutations commonly show pleiotropy often
due to mutation in closely linked genes.
10)Mutations occur in both forward (from wild type allele
to mutant allele) and reverse (from mutant allele to
wild type allele) direction. Generally, the rate of
forward mutations are much higher than those for
reverse mutations
Mutation Breeding
❖ Treating a biological material with a mutagen in order to
induce mutations is known as mutagenesis.
❖ Exposure of a biological material to a radiation like X-
rays, gamma- rays, etc. is known as irradiation.
❖ When mutations are induced for crop improvement, the
entire operation of the induction and isolation, etc. of
mutants is termed as mutation breeding.
❖ Commonly used in self-pollinated & asexually propagated
species while, rarely used in cross pollinated species
❖ A mutation breeding programme should be clearly
planned and should be large enough with sufficient
facilities to permit an effective screening of large
populations.
Situations that favorable for mutation breeding/
Applications of Mutation Breeding
1. When desirable variability is not found in the cultivated
species or in the germplasm of cultivated species .
2. When high yielding variety has oligogenic defect such as
susceptibility to disease.
3. When there is a tight linkage between desirable and
undesirable characters.
4. When particular reaction is to be blocked. For e.g. Opium,
synthesis of morphine by blocking the biochemical pathway at
bane level.
5. In those crop where sexuality is absent.
6. In those species where generation cycle is long, like plantation
crop, fruit tree and forest tree.
7. When flower colour and foliage colour have to be developed in
ornamental plant. Tuberose mutant pict..docx
The various steps involved in
mutation breeding
1. Choice of material: Best adapted variety of a crop
2. Choice of mutagen: Depends upon the plant parts to be
treated various Physical (most preferred for vegetative part)
or chemical mutagens (most preferred for seed) are used.
3. Mutagen treatment: Three things considered
a) Plant species- In seed propagating species generally seeds are
treated and rarely pollen. In vegetatively propagated species,
bulb, corm, cutting or suckers are used for mutagenic treatment.
b) Dose of mutagens- Based on LD50 value. Varies from species to
species.
c) Duration of treatment- Depends on the intensity of radiation or
concentration of chemical mutagen.
4. Handling of treated material: Differ in seed propagated
species (oligogenic and polygenic traits) and vegetatively
propagated species.
Procedure for irradiation
The plant material may be treated in any of the following
source.
1. Seeds: Seeds are used after soaking to get greater
frequency of induced mutations than air dried.
2. Seedlings: At any stage of life cycle can be subjected to
radiation but usually seedlings neither too young nor too old
are irradiated due to their convenience in handling in pots
transportation from nursery easily.
3. Flowers: Meiotic cells have been found more sensitive than
the mitotic cells and therefore plants are irradiated in the
flowering stage in order to affect the developing gametes.
4. Cuttings: In case of fruit tree when they are propagated
by clones – the desirable cuttings are exposed to
irradiation
1. Mutation Breeding in seed propagating
species: Oligogenic traits
2. Mutation Breeding in seed propagating
species: Polygenic traits
3. Mutation Breeding in vegetatively
propagating species
For detail refers to the
Advantages
1. Mutation create inexhaustible variation.
2. When no improvement is possible this method has to be
adopted.
Limitations
1. Frequency of desirable mutations is very low about 0.1
percent. To detect the desirable one in M2 considerable
time, labour & other resources are to be employed.
2. To screen large population, efficient quick and inexpensive
selection techniques are needed.
3. Desirable mutations may be associated with undesirable side
effects due to other mutations thus extending the mutation
breeding programme.
4. Detection of recessive mutations in polyploids and clones is
difficult and larger doses of mutagen have to be applied and
larger populations are to be grown.
Achievements
a) Natural mutants:
Rice : GFB 24 – arose as a mutant from Konamani variety
Dee – Gee – Woo –Gen – Arose as a mutant from rice in China
MTU 20 – arose as a mutant from MTU-3
Sorghum: Co. 18 – arose as a mutant from Co. 2
Cotton: DB 3-12 from G. heroaccum variety Western 1
b) Induced mutants:
Rice : Jagannath-gamma ray induced mutant from T.141
Wheat: Sarbati Sonora Gamma radiation from Sonora 64
NP 836 mutants, through irradiation from NP 709
Cotton: Indore 2 Induced from Malwa upland 4
MLU 7 gamma ray induced mutant from culture 1143 EE
MLU 10 gamma ray induced mutant from MLU 4
Mustard:Primax whicte (1950)
Summer Pope seed Regina I (1953)
Sugarcane: Co.8152 gamma ray induced mutant from Co. 527
Groundnut: NC 4
Castor: Aruna (NPH1) – Fast neutrons induced mutant from HC 6
