The document summarizes the history and process of plant mutagenesis. It discusses how mutation breeding was traced back to 300 BC in China and how the work of Lewis John Stadler in the 1920s-1930s laid the foundation for mutation breeding using X-rays. It also notes that almost 70% of durum wheat and over 400 rice varieties have been developed through mutation breeding programs using physical and chemical mutagens like radiation. The document then explains the key terms, types of mutagens used, factors influencing mutagenesis, types of mutations induced, and the general steps involved in mutation breeding programs.

1. Presented by : Mohaned Mohammed Ali
2017

2. It has been suggested that the history of plant mutagenesis could
be traced back to 300 BC with reports of mutants crops in china.
The work on the induction of genetic alterations through X-rays
by Lewis John Stadler in the late 1920s and early 1930s laid the
foundation of another type of plant breeding known as mutation
breeding.
FAO estimated in 1994 that almost 70% of the durum wheat
initially was mutant varieties and the more than 400 rice varieties
drived from mutagenesis programeme.

3. Terminologies:
 Mutation:
A sudden and heritable change in character of an organism,
which does not arise due to segregation or recombination.
 Mutants:
Individuals carrying a mutation that may be revealed using
molecular means or identified by phenotyping tools.
 Mutagen:
is a physical or chemical agent that changes the genetic material,
usually DNA, of organisms.
 Mutational Breeding :
Utilization of induced mutation for crops development.

4.  Radiation:
It is energy travelling through a distance in the form of
waves or particles.
 Induced Mutation:
It is artificial mutation induced by a treatment which certain
physical or chemical mutagenesis.
Physical mutagenesis:
In the past 80 years physical mutagenesis mostly ionizing
radiations have been used widely for inducing hereditary
aberration and more than 70% mutant varieties were
developed using physical mutagenesis.
The most commonly used physical mutagenesis are show in
the following table:

5. Examples of common physical mutagen:
No Type of
radiation
source Main properties Mode of action
1 X-rays X-ray machine Penetrating and non-particulate Induce mutation by forming free
radicals and ions. Cause addition,
deletion, transition and
transversions.
2 Gamma-rays Radioisotopes and nuclear
reaction
Very Penetrating and non-
particulate
Induce mutation by ejecting atoms
from the tissues.
3 Alfa particles Radioisotopes Less Penetrating, particulate
and positively charged
Act by ionization and excitation.
Cause chromosomal breakage and
gene mutation.
4 Beta particles Radioisotopes Shallowly penetrating Act by ionization and excitation
5 Neutrons Nuclear reactors Penetrating tissue for many
centimeters
Cause chromosomal breakage and
gene mutation.
6 Protons Nuclear reactors Penetrating tissue for several
centimeters
Cause chromosomal breakage and
gene mutation
7 Ion beam Produce positively charged
ions, accelerated at high
speed , deposited high
energy on target
Cause chromosomal breakage and
gene mutation

6. X rays were the first to be used to induce mutation.
The mutagenic effect of ultra violet light was discovered by
Altenbung through irradiation of the polar cap cells of fruit
fly eggs.
Emission of UL light (250-290 nm) has modest capacity of
infiltrate tissues as compared to ionizing radiation.
Ionizing emission goes deeper into the tissue and can cause
a great number of variation in the chemical composition.

7. During the past two decades, ion beams either through
implantation or irradiation have become a new of physical
mutagenesis instead of the widely used gamma rays, x-rays
and neutrons.
Ionizing radiation cause mutation by breaking chemical
bonds in the DNA molecule, deleting a nucleotide or
substitution it with a new one.

8. Factors influencing physical mutagenesis:
Temperature
Moisture content
O2
Dust and fibers
Biological and infection agent (viral and bacterial)

9. The major advantage of physical mutagenesis compared to
chemical mutagenesis is the degree of accuracy and
sufficient reproducibility, particularly for gamma rays,
which have a uniform penetrating power in the issues.

10. Chemical mutagenesis:
The effect of chemical mutagenesis on plant materials is
generally considered milder. They can applied without
complicated requirement equipment. Usually material is
soaked in a solution of the mutagen to induce mutation.
Among chemical mutagenesis is alkylating agent has found
large application in plant experiments. Alkylating agent can
be found in Sulphur mustards, nitrogen mustards and alky
phosphate which lead to modified.

11. Protein activates or affinity like tolerance to herbicide
glyphosate shown in legume Medicago truncatula.

12. Factors influencing chemical mutagenesis:
 Condition of mutagenic solution
 Environment
 Inherit characteristics of target tissue
 Concentration mutagen
 Treatment duration
 Temperature
 Presoaking seed pH(7.0)

13. Examples of common chemical mutagen:
No Mutagen group Example Mode of action
1 Alkylating agents Dimethyl sulphate
(DMS)
React with basses, may degrade to
yield an basic site
2 Antibiotics Mitomycine Chromosomal aberrations also
reported to cause cytoplasmic
male sterlity.
3 Nitrous acid Nitrous acid Acts through deamination
4 Acridines Acridines agent Alteration of the reading frame
5 Azide Azide soudium Same as alkylating agents

14. Type of mutation:
Mutation can be broadly divided into:
 Intragenic (point):
Occuring within a gene in the DNA sequence.
 Intergenic (structure):
Occurring within chromosomes (inversions, translocations,
deletions and duplications).
Mutation leading to change in chromosome number
(polyploidy, aneuploidy and haploid).

15. The key point of mutation breeding is process of identifying
individuals with target mutation, which involves two major
steps:
 Screening:
It is process involving selection of individuals from a large
mutated population that meet specific selection criteria, e.g
early flowering disease resistance as compared to pa rent.
This selection are often regarded as putative mutants.

16.  Confirmation:
It is process of re-evaluating the putative mutants under a
controlled and replicated environment using large samples.

17. Steps in mutation breeding
1- Objective of programme
2- Selection of varieties
3- Plant part treated
4- Does of mutagen (LD50)
5- Giving mutagen treatment (irradiation and chemical)
6- Handling of mutagen treated population

18. Procedures of mutation breeding:
The procedure mutation breeding process consist of four
important steps:
 Choice of material:
The best adapted variety of crop should be chosen for
mutagenesis.
 Choice of mutagen:
The choice of mutagen depend upon the plant parts to be
treated. Generally, chemical mutagens are more preferred for
seed treatment and radiation for vegetative parts treatments.

19. In case of irradiation, the plant parts are immediately planted
rise M1 plant from them (pollen grain are used for
pollination)
In case of chemical mutagen seed are usually presoaked for
a few hours to initiate metabolic activities, exposed to the
desired mutagen and then washed in running tap water to
remove the mutagen present in them.
 Mutagenic treatment:
The procedure of mutagenic treatment takes three thinks into
account which are :

20. Plant species.
Dose of mutagen.
Duration of treatment.
LD50; refer to dose of mutagen that kills 50% of the treated
individuals.
The duration of treatment depend on the intensity of
radiation or concentration of chemical mutagen.

21.  Handling of mutagen treated population:
Treated of seed and vegetative propagules commonly
produces chimaeras. A chimera is an individual with one
genotype in some of its parts and anther genotype in the
others.
Shoot tip meristem usually has three functional layers as
following :
L1 gives rise to epidermis
L2 produce part of leaf mesophyll and gametes

22. L3 yield the rest of plant body
When the whole L1, L2 and L3 layer is affected, the
chimaera is known as Periclimal chimaera, while in
sectional chimaera only part of L1, L2, L3 layer is affected.
In sexual reproducing species, only the L2 ( Periclimal ,
sectional ) will be transited to the next generation.

23. Thank you