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test their suitability to be integrated in breeding programs. They established that
the PCR based markers are the simplest, most accurate, lowest cost technique and
therefore recommended this method for the identification of Glu-A3 and Glu-B3 al-
leles in breeding programs. However, the combination of different techniques was
required to identify certain alleles, and would be especially useful when character-
izing new alleles from new genetic resources. They also recommended a standard
set of 30 cultivars for use in future studies to represent all LMW-GS allelic variants
in the collection.
Gliadins
In wheat storage proteins, gliadin is an important fraction that accounts for about
40-50 % of the total proteins. It has great impact on processing and nutritional
quality of flour, followed by HMW-GS and LMW-GS. Gliadins are soluble in 70 %
ethanol and are heterogeneous mixtures of single-chained polypeptides. Gliadins
can be seperated in A-PAGE (acid-PAGE) based on the differences in their mobil-
ity. The four different groups identified include α-, β-, γ-, and ω-gliadins, of which
α- gliadins has fastest while ω-gliadins has slowest mobility. Gliadins are controlled
by Gli-1 loci, which are complex and comprise the ω-gliadin and γ-gliadin (Me-
cham et al. 1978 ) multi-gene families (Harberd et al. 1985 ), which in some circum-
stances may be divided into Gli-1-1 and Gli-1-2 , respectively. The LMW glutenin
multigene families, which are closely linked to the Gli-1 loci (Jackson et al. 1983 ),
are listed separately as the Glu-3 set (Singh and Shepherd 1985 ); information on
map distance and gene order in relation to Glu-3 and the centromere is given in the
preamble for the Glu-3 loci.
Gene Expression and Polymorphism
It was identified that short arms of group 1 and group 6 chromosomes encode glia-
din genes. The genes present on Gli-1 loci are controlled by Gli-A1 , Gli-B1 , and
Gli-D1 loci on 1AS,1BS and 1DS, respectively. Similarly, Gli-2 genes are con-
trolled by Gli-A2 , Gli-B2 , and Gli-D2 loci on chromosomes 6AS, 6BS and 6DS,
respectively. The genetic analysis revealed that all ω- and many γ-gliadins are en-
coded by Gli-1 loci and all α-, many of β-, and some of γ-gliadins are encoded by
Gli-2 loci. The gene clusters of gliadins encode polypeptides as Mendalian factor
and multiple allelism phenomenons have been observed at both loci (Metakovsky
1991 ). In MacGene (2010), 23 alleles are listed for Gli-A1 , 24 for Gli-B1 and 15
alleles for Gli-D1 in bread and durum wheat. Similarly, among Gli-2 loci, Gli-A2
encodes 36 alleles, Gli-B2 encodes 47 and Gli-D1 encodes 31 alleles. Apart from
these two loci, several workers reported many other loci. These include Gli-3 (4 al-
leles at Gli-A3 and 3 alleles at Gli-B3 ) coding for ω-gliadins on short arms of group
1 chromosomes (Galili et al. 1984 ; Sobko 1984 ), Gli-5 (2 alleles at both Gli-A5 and
Gli-B5 loci) coding for ω-gliadins on short arm of chromosomes 1A and 1B distal
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