Mutagenesis—A Potential Approach for Crop Improvement - Crop Improvement: New Approaches and Modern Techniques - page 161

Fig. 4.5 The diagrammatic view of the gamma ray source and associated apparatus in gamma
phytotron. (Modified from Kang et al. 2010 )
the growth conditions of targeted plants (Fig. 4.5 ). The difference of mutagenic ef-
fects of the acute and chronic irradiation can be compared using the same treatment
dose. It is expected that the heavy applications of the chronic gamma phytotron will
be extended to various crop plants, which are eventually provided to domestic and
global communities for mutation breeding and fundamental research.
ChemicalMutagenesis
The use of chemical mutagens is also very simple and can be done in any bio-
logical laboratory with basic equipment. However, it should be kept in mind that
most chemical mutagens are also strong carcinogens. For this reason, all steps of
mutagenic treatment should be carried out wearing gloves and under a Biohazard
flow-hood. These safety conditions are not necessary for treatment with sodium
azide, which is a very powerful mutagen, but only for a limited number of species,
including barley, rice, maize, oat, sorghum, sesame, jute and soybean. Numerous
chemical mutagens have been successfully used for crop improvement.
The mutagenic action of a chemical mutagen induces somatic and genetic effects
in a treated cell, tissue or organ. After treatment of seeds, only unrepaired damage
to the DNA in initial cells of the sporogenic layer (germ line cells) are transferred
as mutations to the next generation. Other mutations in somatic cells of the embryo,
including mitotic chromosomal aberrations, together with toxic action of a muta-
gen on all components of cytosol, affect plant growth and development, and are
called the 'somatic effect' of the mutagen. The steps generally followed in muta-