Mutagenesis—A Potential Approach for Crop Improvement - Crop Improvement: New Approaches and Modern Techniques - page 167

Mutagenesis and Genetic Variability
Diversifying the limited genetic variability for agronomic traits of interest, espe-
cially yield and its associate attributes and developing new crop cultivars are much
demanding in this modern era (Roychowdhury et al. 2012 ). Due to lack of suf-
ficient natural variability, the mutation breeding performance in crop species can
significantly accelerate many breeding endeavors, which have proven difficult with
classical breeding procedures (Roychowdhury 2011 ; Roychowdhury et al. 2011 ).
Various metrical attributes like seed weight, number of branches, leaves, flowers,
leaf area, etc., are very much complex in nature because it is governed by polygenes
and greatly influenced by environmental factors (Roychowdhury et al. 2011 , 2011c ,
2012 ). This may raise breeder's concern, since the genetic organization provides
the base for crop enhancement of environmental adaptation, yield and other associ-
ated attributes. The presence of adequate genetic variability between treatments of
a cultivar is critically important (Fasoula and Fasoula 2002 ). Moreover, the genetic
progress in a breeding program is actually dependent on the variation in the pres-
ent gene pool (Dreisigacker et al. 2004 ) associated with the magnitude of several
genetic parameters.
It is a powerful and effective tool in the hands of plant breeders for self-pol-
linating crops having narrow genetic base as well as for cross-pollinating crops
(Micke 1988 ). The success of any breeding program depends to a large extent on
the amount of genetic variability present in the population. The role of mutation
breeding in increasing the genetic variability for desired traits in various crop plants
have been proved beyond doubt by a number of scientists (Tah 2006 ; Adamu and
Aliyu 2007 ; Khan and Goyal 2009 ; Kozgar et al. 2011 ; Mostafa 2011 ; Kozgar et al.
2012 ). Wide spectrum of genetic variability has been induced using both physical
and chemical mutagens in order to utilize it in crop improvement and inheritance
studies (Patil 1966 ; Ashri 1970 ; Gowda et al. 1996 ). Induced mutations have been
used to generate genetic variability and have been successfully utilized to improve
yield and yield components of various crops like Oryza sativa (Singh et al. 1998 ),
Dianthus caryophyllus (Roychowdhury and Tah 2011b ), Solanum melongena (Roy-
chowdhury et al. 2011c ), Cicer arietinum (Kozgar et al. 2012 ), Vicia faba (Ismail
et al. 1977 ), Vigna radiata (Wani and Khan 2006 ; Roychowdhury et al. 2012 ),
Vigna unguiculata (Mensah and Akomeah 1992 ), Cajanus cajan (Srivastava and
Singh 1996 ), Vigna mungo (Singh and Singh 2001b ) and Lens culinaris (Khan et al.
2006 ). These reports show that mutagenesis is a potential tool to be employed for
crop improvement.
Overall variability must be partitioned into heritable and non-heritable compo-
nents with the aid of genetic parameters such as genotypic and phenotypic coef-
ficients of variation, heritability and genetic advance (Ariyo 1987 ; Roychowdhury
and Tah 2011b ; Roychowdhury et al. 2011a , 2011c , 2012 ). Genetic variability stud-
ies provide basic information regarding the genetic properties of the population
based on which breeding methods are formulated for further improvement of the
crop. These studies are also helpful to know about the nature and extent of vari-