Agriculture Reference
In-Depth Information
on experimental background, and third-one is solely based on computer
models. It is equal to the universal truth that the effect of climate change
is omnipresent, and therefore, it is applicable to most of the existing issues
like plant disease (in particular - air pollution, Fig. 10.1 ). Hence, a holistic
approach is needed to address many issues that are already appearing in
agriculture, horticulture, forestry and conservation of the complete ecol-
ogy (O'Halloran et al., 2012).
10.3
VARIABLES INFLUENCING PHYTOPATHOSYSTEMS
The development of plant disease is occurred by three important factors:
(i) susceptible host, (ii) virulent and compatible pathogen (and vector if
desired), and (iii) favorable environment (Vanderplank, 1963). It is impor-
tant to induce a successful infection that all three of these factors must be
at right position, at particular degree and at appropriate time ( Fig. 10.2 ).
Modification among one of the mentioned variables leads to evolve an
altered phytopathosystem. For example, enhanced silicon content in rice
plant reduces the chances to M. oryzae infection (Nakataa et al., 2008;
Seebold et al., 2004). In other view, the lower epidemics may attain in the
presence of the local race (of the pathogen) under uncongenial environ-
ment. Life strategies are governed by some behavioral adaptations by the
plant pathogens. There are two kinds of strategists found in the world of
pathogen: (i) r strategist-responsible for compound interest disease and (ii)
K strategist-responsible for simple interest disease (Zadoks and Schein,
1979). The black (stem) rust pathogen P. graminis f. sp. tritici belongs to
the r strategist group particularly at uredial stage. The organization is set
up in such a way that the whole biomass is divided into 50% mycelium
and 50% spore devoted to dispersal. This fungal pathogen is eligible to re-
produce 2000 spores per day and 20,000 spores during its lifespan from a
pustule developed with a single spore. Contradictorily the K strategists are
poor producer of functional dispersal unit and without known functional
spore, for example, Sclerotium rolfsii . For both of the strategist inoculum
potential, genetic shift and recombination are the key determinants that
decide virulence of the pathogen (Figs. 10.2 and 10.3 ). It is a matter of
chance that the disease may develop at a condition when host, pathogen
and environment interact in a compatible manner.
 
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