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Spot blotch
caused by Bipolaris sorokiniana is a
major devastating disease of wheat and barley in South Asia particularly the
region of EGP (Eastern Gangetic Plains), India. This disease mainly occurs on
the foliar part of plants but some other parts of are also affected such as
root. This disease is also affects the
end-use quality of harvested wheat grains (Mehta, 1998). Different worker estimates the area
and losses of grain yield in wheat caused by this disease. Approximately 25 mha area of wheat is affected by this disease
(van Ginkel and Rajaram, 1998). In which ~ 40% area is present in the Indian
sub-continent (Joshi et al., 2007a), where the crop losses occurs upto 25% (Dubin and van
Ginkel, 1991). The yield loss in individual fields is sometimes much higher.

Several works have been made in
recent past to the identification of spot blotch disease resistance mechanism
at the molecular level but could not resolved this puzzle thoroughly. In this
series, resistance QTLs have been identified by a number of workers in
different laboratory (Kumar et al.,
2009, 2010; Adhikari et al., 2012;
Gurung et al., 2014). Additionally,
major spot blotch resistance genes (Sb1,
Sb2 and Sb3) are also
characterized recently (Lillemo et al.,
2013; Kumar et al., 2015; Lu et al., 2016). The major resistance genes
and QTLs provides the advantage during the intogression in well adopted
cultivars through Marker Assisted Selection (MAS) but both are also affected by
the genetic background of genotypes and also locations.

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During the recent
advance in the science of disease resistance mechanism at the molecular levels,
the role of epigenetic modification in disease resistance can provide a way to
resolve this problem.  However, no work
have been done about the role of epigenetic processes during the regulation of
spot blotch resistance so far. Although, it has been shown that
resistance in the host and virulence of the pathogen in any pathosystem may be
partly controlled by epigenetic modifications.

The work involving the role of methylation/demethylation and
chromatin remodelling involving histone modifications in plant immunity has
recently been reviewed (Ding & Wang, 2015; Deleris et al., 2016). Genome wide
profiling of histone modifications (H3K9me2 and H4K12ac) and gene expression
has also been conducted in common bean (Phaseolus vulgaris) inoculated with
rust (Uromyces appendiculatus) (Ayyappan et al., 2015).

DNA methylation patterns can be estimated using one or more of the
following approaches: restriction enzyme based methyl sensitive amplified
polymorphism (MSAP), methyl-sensitive PCR (MS-PCR), bisulphite whole genome
sequencing (Bis-Seq) or methylated DNA immunoprecipitation (MeDIP) (Gupta et al., 2017). Genomic regions involved
in DNA methylation as well as histone modification can also be identified using
chromatin immuno-precipitation bisulphate sequencing (ChIP-Bis-Seq).

Methylation and histone modification in individual genes of interest can also be
undertaken using amplified-fragment single nucleotide polymorphism and
methylation AFSM; also called methyl sensitive genotyping by sequencing (ms-GBS),
MS- PCR and ChIP-PCR.

    Restriction enzyme-based assays use methylation sensitive or
dependent restriction enzymes to digest genomic DNA, followed by detection of
target regions by either hybridization, or PCRs, or sequencing. These methods
are limited to the analysis of a specific genomic region and often report the
methylation level of only a small number of positions. The MeDIP
(immunoprecipitation of methylated DNA) method takes advantage of antibodies
that can specifically recognize 5-methylcytosine at the nucleotide of DNA.

After immunoprecipitation of methylated DNA, array or sequencing based methods
are used to profile genome-wide DNA methylation levels (Zhang et al., 2016; Eichten et al., 2011; Ding et al., 2014).

            The methylation levels in different species are not common (Feng
et al., 2010; Zemach et al., 2010; Niederhuth et al., 2016) and show variable patterns
in different species (Baulcombe et al.,
2014). These patterns can affects the function of DNA methylation at different
levels such as gene expression, transposon repression, and response to biotic
as well as abiotic stresses (Xiao and Wagner, 2015; Kawakatsu ?et al., 2016)

            The DNA methylation patterns has
abilities to provide the opportunities for single-base resolution, enhanced
understanding of various aspects of DNA methylation, including genetic
regulation, trans-generational inheritance, genetic variation and also 

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