Gene pyramiding and omics approaches for stress tolerance in leguminous plants - Legumes Under Environmental Stress: Yield, Improvement and Adaptations - page 268

Founding parents

P1 XP2 P3X P4 P5 XP6 Generation 0

H (1) (2) H (3) (4) H (5) (6) Generation 1

H (5) (6) Generation 2

H (1, 2) (3,4)
(Node)

H (1, 2, 3,4) (5,6)
(Root genotype)

Generation 3

Sel � ng and selecting genes for the presence of target genes

Target genotype
H (1, 2, 3,4, 5,6) (1, 2, 3,4, 5,6)

Figure 16.2 Example of gene pyramiding scheme accumulating six target genes. P1-P6: founding parents; H: hybrids. Adapted from
Servin et al . (2004).

all genetic markers have particular genomic positions
within chromosomes known as loci (Collard et al., 2005).

markers in major cereals and legumes (Gupta et al.,
1999; Gupta & Varshney, 2000).

16.2.1.4 Types of genetic markers
There are three major types of genetic markers (Lan &
Chao, 2011).
1 Morphological markers, which are phenotypic traits
or characters such as flower colour, seed shape or
growth habits.
2 Biochemical markers; these include the variants of
enzymes called isozymes, which are detected by using
electrophoresis and specific staining.
3 DNA (or molecular) markers, which are most widely
used and reveal variations of the DNA. Different types
of DNA markers are used in several crops. Commonly
used DNA markers are: simple sequence repeats (SSRs)
or microsatellites; sequence characterized amplified
regions (SCARs) or single nucleotide polymorphisms
(SNPs); sequence tagged sites (STSs); restriction
fragment length polymorphisms (RFLPs); randomly
amplified polymorphic DNA (RAPD); amplified
fragment length polymorphisms (AFLPs); inter simple
sequence repeats (ISSRs); expressed sequence tags
(ESTs), cleaved amplified polymorphic sequences
(CAPSs) and diversity arrays technology (DArT)
(Panigrahi et al., 2013). Simple sequence repeats
(SSRs) or microsatellites are the most widely used

16.2.1.5 Marker-assisted selection in legumes
The use of MAS may be advantageous for improving
different crop varieties but its application in legumes is
limited for combating stress mainly due to a lack of
investment and the genetic complexity of traits related
to stress (Dita et al., 2006). But there are exceptions
where successful adoption of MAS has been reported in
certain legumes against important biotic stresses.
Techniques including genetic engineering and marker-
assisted breeding have been used for improving
chickpea. A soybean variety resistant to cyst nematode
was developed using MAS (Diers, 2004). Other exam-
ples of the application of MAS include pinto bean
resistant to common bacterial blight (Mutlu et al., 2005),
and narrow-leafed lupin ( Lupinus angustifolius L.) resis-
tant to phomopsis stem blight (Yang et al., 2002) and
anthracnose (Yang et al., 2004). Several other studies
have also reported the introgression and pyramiding of
genes of interest and quantitative trait loci (QTLs) in
legumes, but gene pyramiding assisted by MAS has been
reported only in few studies such as in common bean
breeding for rust and anthracnose resistance (Faleiro
et al., 2004). Kelly and Vallejo (2004) described several
molecular markers linked to the genes conferring