the presentation briefly describes various mutagenic agents used in crop improvement also gives a comparative study on effectiveness and efficiency of physical and chemical mutagens.

1. Ananda Lekshmi.L
2018600801
Comparative evaluation of
physical and chemical
mutagens
GPB 610 Mutation Breeding (1+1)

2.  MUTATION : Sudden heritable change in the characteristics of an
individual or permanent change in the number , kind and sequence
of nucleotides in the genetic material.
 Genetic improvement of crop plants for various economic
characters through the use of induced mutations is referred to as
mutation breeding.
 Commonly used in self pollinated and asexually propagated species.
 Induced mutations are defined as inheritable changes in DNA of
qualitative or quantitative order, not derived from genetic
segregation or recombination.
MUTAGENS IN PLANT BREEDING

3.  Since spontaneous mutation rates are very low, induced mutations
are being used to increase its rate and frequencies
 Mutations can be induced either by chemical, i.e., alkylating
(ethylmethanesulphonate) or physical agents like ionic radiation
(Predieri 2001).
 Alterations in the DNA of the nucleus or organelles give rise to
gene, genome, or chromosome mutations that generate variability,
(Tulmann Neto et al. 1998).
 The direct use of mutations is helpful, especially when the
improvement of one or two easily selectable traits in a well adapted
variety

4.  Main advantage is that the basic genotype is only slighty altered,
by contrast to procedures involving crossing of two distinct
varieties (Donini and Sonnino 1998).
 Technical aspects of mutation breeding:
1. choice of the mutagenic agent,
2. dose,
3. ratio between mutation frequency and dose.
4. population size,
5. handling of the treated tissue or organ,
6. appropriate selection methods.

5.  Mutation inducing is a tool that could increase the genetic variability in
crops where the cultivated germplasm has a narrow genetic basis
 The usefulness of any mutagen in plant breeding depends not only on
its mutagenic effectiveness, but also on its mutagenic efficiency,
efficient mutagenesis.
 It should give of the maximum desirable changes accompanied by the
least possible undesirable changes.

6.  Two agents may be equal in mutagenic effectiveness because, at a
given dose, they induce a mutation with the same frequency.
 when they diverge in their ability to produce undesirable changes
such as sterility and lethality then they may be said to differ in
mutagenic efficiency.
 Ionizing radiations such as gamma -rays are highly effective in
inducing chromosomal aberrations whereas mutagens such as EMS
act primarily on base pairs of the DNA molecule and yield a higher
number of gene mutations.
 Because of the basic mechanistic difference between these two
groups of mutagens, chemical mutagens are generally considered to
be superior to physical mutagens for induction of mutation.

7.  Ionizing radiations such as X-rays, gamma rays and alpha
particles cause DNA breakage and other damages.
 Radioactive decay, such as 14C in DNA which decays
into nitrogen.
 Ultraviolet radiations with wavelength above 260 nm are
absorbed strongly by bases, producing pyrimidine dimers, which
can cause error in replication if left uncorrected
MODE OF ACTION OF DIFFERENT
MUTAGENS

8.  Base analog, which can substitute for DNA bases during
replication and cause transition mutations.
 Intercalating agents, such as ethidium bromide and proflavine,
are molecules that may insert between bases in DNA,
causing frameshift mutation during replication.
 Some such as daunorubicin may block transcription and
replication, making them highly toxic to proliferating cells.

9.  Arsenic, chromium, iron, and nickel may be associated with the
production of ROS, and some of these may also alter the fidelity
of DNA replication.
 Nickel may also be linked to DNA hypermethylation
and histone deacetylation, while some metals such as cobalt,
arsenic, nickel and cadmium may also affect DNA repair
processes such as DNA mismatch repair, and base
and nucleotide excision repair.

10. CASE STUDY

12.  Three sesame (Sesamum indicum L.) genotypes (Rama, SI 1666
and IC 21706) were selected for this study.
 In this they have examined the mutagenic effectiveness and
efficiency of different doses of gamma ()-radiation and ethyl
methane sulphonate (EMS) on the genetic variability of sesame in
the M2 and M3 generations.
Gamma radiation treatment:
 Dry seeds (10%-12% moisture content) of each genotype were
exposed to one of three doses (200 Gy, 400 Gy and 600 Gy) of -
rays derived from 60Co.
 Three hundred seeds per genotype were treated with each dose of
radiation.
SESAME CASE STUDY;

13. EMS treatment:
 In the case of EMS, seeds (150 per concentration) were exposed
to one of four concentrations of the chemical (0.5%, 1.0%, 1.5%
and 2.0% in phosphate buffer of neutral pH) for 6 h with
intermittent shaking.
 The treated seeds were then washed with water, dried with
filter paper and immediately sown in the field.
 The seeds were sown in RBD with 3 replications.

14.  The results for the M2 generation revealed that lower doses
of mutagens were effective and efficient in causing
polygenic variability in various quantitative characters, with
a negative relationship between effectiveness and mutagen
dose.
 The lowest concentration of EMS (0.5%) was the most
effective in causing mutations. The average effectiveness of
EMS was several times higher than gamma rays.
 Interestingly, gamma rays were more efficient in inducing
mutations, with a lower dose of gamma-rays showing a
higher mutagenic efficiency.
COMPARISON

16.  In this healthy and pure seeds of two varieties of
ricebean viz., BRS-1 and Totru Local were treated with
gamma rays (30, 40 and 50 kR) and ethyl methane
sulphonate (EMS) (0.50, 0.60 and 0.70%).
 A steady reduction in germination and subsequent
survival of the treated population and seedling height
reduction was observed with the increasing
dose/concentration of mutagens in both the cultivars
regardless of the mutagens used.
RICE BEAN CASE STUDY:

17.  Its found that EMS was almost four times more effective and
two times more efficient than gamma-rays.
 And they observed that both mutagenic effectiveness and
efficiency decreased with an increasing doses/ concentrations of
mutagens .
 The lower doses (30kR in gamma rays and 0.50% in EMS) were
found to be the most important doses for inducing desirable
variability in ricebean

18.  Sowing of M1 generation was done immediately after treatment
with the mutagen.
Results:
The initial damage caused by the mutagenic treatments was
scored by recording the reduction in germination and
subsequent survival of the treated plants and seedling height
reduction (injury) in M1 generation.
On the joint survey of gamma rays doses over BRS1 and
Totru Local, 30 kR and of chemical mutagen 0.50% EMS were
the most suitable doses for producing mutagenized populations
with high magnitudes of variability.

20.  The study was conducted in 1997 and 1998, in the field and
greenhouse, at the Federal University of Pelotas, in Capão do
Leão, State of Rio Grande do Sul, Brazil.
 Nearly 1200 genetic seeds from four fixed hexaploid oat
populations (CTC 3, UFRGS 10, UFRGS 14, and UPF 16) were
gamma ray-treated under a 60Co source and subjected to
ethylmethanesulphonate (EMS), thus originating the M1
generation.
 The total doses of irradiation and absorption were 100; 200 and
400 Gy and 0.5; 1.5 and 3.0% per treatment of physical and
chemical agents, respectively, coded as doses 1, 2 and 3.
 The physical mutagen engendered superior estimated values of
variance in most populations, independently of the tested dose
GENETIC VARIABILITY IN OATS
CASE STUDY;

21.  In general, micromutations were once more predominant,
compared to macromutations.
 the dose of mutagen (EMS) increases, the plant height is reduced
to a certain point in the studied period
.
 Results :
The physical mutagen was more efficient at changing the
genetic variability of the great majority of the studied populations.
 the use of physical mutagens can induce the occurrence of new
genes through allelic and/or chromosomal changes.

23.  Present study was carried out with the eggplant (Solanum
melongena) variety Pusa Uttam to test the mutagenic
effectiveness and efficiency of gamma ray, methyl methane
sulphonate (MMS), dimethylsulphate (DMS) and diethyl sulphate
(DES) to induce maximum macro-mutations which could
eventually be exploited in future as viable and economically
important traits.
 Dry and healthy seeds (10-12% moisture content) of variety Pusa
Uttam were treated with different doses/ concentrations of gamma
ray (5, 10, 15, 20 and 15 kR), MMS (0.05, 0.075, 0.10, 0.25 and
0.50%), DMS and DES (0.10, 0.25, 0.50, 0.75 and 1%).
Solanum melongena CASE STUDY:

24.  the lower or intermediate treatments of gamma rays as well as the
alkylating agents were found more effective and efficient in creating
maximum mutations with less biological damage.
 The order of mutagenic effectiveness was MMS>DMS>DES>gamma
ray.
 The order of mutagenic efficiency with regard to inhibition in
germination (Mp/I) was same as the effectiveness
 the orders of efficiency with regard to pollen sterility (Mp/S) was
DMS>DES>MMS>gamma ray
 The alkylating agents were found to be more potent than gamma rays in
effectively and efficiently widening the genetic base of egg plant
RESULTS

25.  Genetic variability induced by chemical and physical mutagenic
agents in oat genotypes :Jefferson Luís Meirelles Coimbra1*,
Fernando Irajá Félix de Carvalho1 and Antônio Costa de Oliveira1
 Comparative Mutagenic Effectiveness and Efficiency of Physical
and Chemical Mutagens in Solanum melongena L. Variety Pusa
Uttam Danish Shahab*1,3, Mohd Gulfishan2, Afaq Ahmad Khan3,
Csaba Vágvölgyi1 and Mohd Yunus Khalil Ansari3
 A comparison of the effects of physical and chemical mutagens in
sesame (Sesamum indicumL.) Tamina Begum; Tapash Dasgupta*
Department of Genetics and Plant Breeding, Institute of Agricultural
Science, University of Calcutta, Kolkata, India
 Comparative mutagenic effectiveness and efficiency of physical and
chemical mutagen and induced variability in ricebean (Vigna
umbellata Thunb, Ohwi and Ohashi) Madhu Patial*, S.R. Thakur1 and
K.P. Singh
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