Variability in Fusarium species Causing Wilt Disease in Crops: A Transcriptomic Approach to Characterize Dialogue Between Host and Pathogen - Crop Improvement: New Approaches and Modern Techniques - page 271

Plant-Fungi Interaction
The wilting caused by Fusarium is result of various factors guided by host-pathogen
interaction such as recognition of pathogen by plant root, attachment of pathogen
by differentiated structure, penetration of the pathogen to have access to vascular
tissue, adaptation of pathogen within the plant system, the proliferation of fungal
components (hyphae and microconidia) in xylem vessels and lastly the secretion
by the pathogen (proteins and toxins) (Inoue et al. 2002 ; Di Pietro et al. 2003 ). The
primary defense response by the host includes the production of gums, tyloses and
gels (Beckman 1987 ). Thus, there is the need for understanding host-pathogen asso-
ciation in terms of infection process (at molecular level), which would provide the
information about the mechanisms of this interaction. The study of this interaction
will unravel the genes involved in different signaling cascades, which would help
us in identifying genes involved in resistance as well as susceptibility. This kind of
association ( Fusarium -Tomato) study has been recently reported as a model system
for infection process (resistance and susceptibililty) at molecular level (Takken and
Rep 2010 ). Further, some processes related to mechanisms of infection resistance
have been determined by molecular techniques such as gene silencing or insertion
mutagenesis (Inoue et al. 2002 ; Di Pietro et al. 2003 ; Michielse 2009 ). The knowl-
edge about the infection resistance or susceptibility in agricultural crops would help
us in better understanding about the development of strategies in controlling the
disease factors such as infection responses and progression. For example, mRNA
changes in association (host-pathogen) during the infection process could give in-
formation about the resistance and susceptibility processes (Wise et al. 2007 ).
Use of DNA Based Markers
The advances and development in molecular biology techniques and its applications
to genetic analysis has led to better understanding in terms of knowledge which has
led to elucidation of behavior and structure of fungal genome. For example, these
advances have helped the fungal taxonomists in identification of isolates more rap-
idly and for determining virulence/toxicity of fungal strains. The advances in mo-
lecular biology led to distinction between species (closely related) having little or no
similarity at the morphological level (Wulff et al. 2010 ) or strain identification with-
in species (Chandra et al. 2010 ). And thus by looking for the variation within DNA
sequences, the molecular biology provides the base for precise identification within
and between the species. The Polymerase chain reaction (PCR) based assays are be-
ing employed widely used for identification, diagnosis and characterization of patho-
gens ( Fusarium species) (Doohan et al. 1998 ). Various PCR based markers are in use
(Nayaka et al. 2011 ), which has led to the understanding of genetic diversity and
establishing phylogeny among different Fusarium species. The PCR based methods
which have been used to generate sequence information include RFLP, AFLP,