Mutagenesis—A Potential Approach for Crop Improvement - Crop Improvement: New Approaches and Modern Techniques - page 155

causing pollen abortion cannot be transmitted gametophytically to future genera-
tions; consequently homozygous plants with all aborted pollen are lost in the cause
of evolution.
Mutation and mutation breeding is a tool and being used to study the nature and
function of genes which are the building blocks and basis of plant growth and de-
velopment, thereby producing raw materials for genetic improvement of economic
crops (Adamu and Aliyu 2007 ). Mutation induction offers significant increase in
crop production (Kharkwal and Shu 2009 ) and the possibility of inducing desired
attributes that either cannot be found in nature or have been lost during evolution.
Treatment with mutagens alters genes or breaks chromosomes. Gene mutations oc-
cur naturally as errors in DNA replication. Most of these errors are repaired but some
may pass to the next cell division to become established in the plant offspring as
spontaneous mutations. Gene mutations without phenotypic expressions are usually
not recognized. Consequently, genetic variation appears rather limited and breeders
have to resort to mutation induction (Novak and Brunner 1992 ; Kozgar et al. 2012 ).
Mutagenic agents have been used to induce useful phenotypic variations in plants
for more than seventy decades (Vasline et al. 2005 ; Roychowdhury et al. 2011 ).
During the past 70 years, more than 2,543 mutant cultivars from 175 plant species
including ornamentals, cereals, oilseeds, pulses, vegetables, fruits and fibers have
been officially released in 50 countries all over the world (Maluszynski et al. 2000 ;
Chopra 2005 ). Chemical mutagenesis (the non-GMO approach) is an approach to
create mutation in plants for their improvement of potential agronomic traits. In
any mutation breeding programme, selection of an effective and efficient mutagen
is very essential to produce high frequency of desirable mutation. Many chemical
mutagens have been employed for obtaining useful mutants in various crop spe-
cies (Singh and Singh 2001a ; Roychowdhury and Tah 2011c ; Roychowdhury et al.
2012a ). However the various workers emphasizes that artificial induction of muta-
tion by colchicine (COL), ethyl methane sulphonate (EMS), sodium azide (SA),
maleic hydrazide (MH) provides tool to overcome the limitations of variability in
plants and induces specific improvement without disturbing their better attributes
(Mensah and Obadoni 2007 ; Islam 2010 ; Roychowdhury 2011 ; Roychowdhury and
Tah 2011 ; Roychowdhury et al. 2011b ; Gnanamurthy et al. 2012 ). It might be con-
sidered that, these chemical induced growth abnormalities were mainly due to cell
death and suppression of mitosis at different exposures. Several factors such as
properties of mutagens, duration of treatment, pH, pre- and post-treatment, tem-
perature and oxygen concentrations, etc. influence the effect of mutagens. The dose
of a mutagen applied is an important consideration in any mutagenesis programme.
Generally, it was observed that higher the concentrations of the mutagen greater
the biological damage. To enhance the mutagenic effectiveness and efficiency and
especially the metabolite, more knowledge about the effect of time, pH value, tem-
perature, seed soaking and various concentrations are required (Khan et al. 2009 ;
Roychowdhury and Tah 2011a , 2011c ; Roychowdhury et al. 2012a ). Crop plants of-
fers many opportunities exploitation of mutations, recombination and of increasing
genetic variability in quantitatively inherited agronomic characters. Induced muta-
tions are also useful when it is desired to improve easily identifiable characters.