Post harvest diseases fruits and vegetables - Xavier University ...

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
52 Postharvest Diseases of Fruits and Vegetables
defense capability of the host will dictate the success or failure of the
infection. The attack mechanisms of the pathogen and the defense
mechanisms of the host are summed up in Table 3.
TABLES
Attack mechanisms of the pathogen and defense
mechanisms of the host
Attack mechanisms of the pathogen:
1. The ability to produce cuticle- and cell wall-degrading enzymes.
2. The ability to produce toxins causing cell death.
3. The ability to detoxify resistance compounds in the host.
4. The ability to develop on the fruit and vegetable surfaces, and within
their tissues.
Defense mechanisms of the host:
1. The ability of the intact cuticle to provide a barrier to fungal
penetration; its ability to prevent diffusion of cellular solutions, so
limiting water and nutrient availability on the plant surface.
2. The resistance of the young fruit and vegetable cell wall to
degradation by the pathogen enzymes.
3. The presence of preformed (constitutive) compounds inhibiting
pathogen growth and enzymatic activity, and the ability to further
induce, or enhance their production.
4. The ability to produce low molecular-weight secondary metabolites
with antimicrobial activities, phytoalexins, in response to fungal
penetration or other stress conditions.
5. Wound healing and the formation of barriers against the progress of
the pathogen and its enzymatic activity; reinforcement of plant cell
walls by formation of glycoproteins, callose, lignin and other phenolic
polymers; the formation of papillae and plugging of intercellular
spaces.
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