Agriculture Reference
In-Depth Information
provided; however, the response to a particular nutrient may be different when going from
defi ciency to suffi ciency than from suffi ciency to excess (Huber & Haneklaus, 2007).
Not only the supply of an individual nutrient, but balanced, crop-specifi c nutrient ratios,
which adequately supply the plant during its development, and in varying environmental
conditions, are crucial for improving plant health. Through an understanding of disease
interactions with each specifi c nutrient, the effects on the plant, pathogen and environ-
ment can be effectively modifi ed to improve disease control, enhance production effi -
ciency and increase crop quality (Huber & Haneklaus, 2007). In Figure 11.1, a schematic
illustration of interacting compartments involved in plant disease is shown.
Under unfavourable conditions, time-dependent interactions between plant, pathogen
and environment will result in infection of the plant by fungal pathogens (Figure 11.1). The
nutritional status with essential plant nutrients and their balance contribute signifi cantly
to the physiological predisposition of a plant against fungal infections. Experimentation
in the fi eld of sulphur (S) nutrition and plant disease provided added indications that the
S status of a plant is particularly critical during the initial phase of pathogenesis, and if
several stress factors coincide, while its signifi cance declines with spread of the disease in
the host (Salac
et al.
, 2006; Bloem
et al.
, 2007; Haneklaus
et al.
, 2007a). In this context
it should be noted that evaluating the nutritional status of a plant correctly is not as easy
as commonly assumed. Nevertheless, such assessment is indispensable for determining
the infl uence of the nutritional status on susceptibility against fungal pathogens. There is
not even one exclusive critical nutrient value for each crop, as it depends on the growth
conditions, the developmental stage of the plant at sampling, the collected plant part, the
determined S species, the targeted yield and mathematical approach for calculating it
Plant
Genetic and physiological predisposition
Plant/Environment sustaining interaction
Time
Environment
Disease
Coincidence of
virulence
and susceptibility
Abiotic and biotic
stress
Plant/Pathogen incompatibility
Pathogen
Virulence
Figure 11.1
Schematic illustration of interacting components involved in plant disease.
