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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
CHAPTER 12
NOVEL APPROACHES FOR ENHANCING HOST
RESISTANCE
Synthetic fungicides are currently the primary means used for
controlhng postharvest diseases. The resistance developed by postharvest
pathogens to some fungicides, and the withdrawal of a number of key
fungicides in response to health concerns over pesticide contamination,
have stimulated the search for alternative technologies for postharvest
disease control. Among the various possible alternative means of
control, much attention has been drawn to the wide range of natural
substances with antimicrobial activity. Plant- and animal-derived
fungicides may offer safe alternatives to synthetic fungicides (Wilson et
al., 1994), and the potential use of these antimicrobial agents is
discussed in the chapter. Chemical Control - Natural Chemical
Compounds. Other alternatives to chemical treatments are the various
physical means of suppressing postharvest decay development. These
are discussed in the chapters. Means for Maintaining Host Resistance,
and Physical Means. The use of antagonistic microorganisms, often
isolated from plant surfaces, as biocontrol agents is another alternative
and quite promising direction. The chapter on Biological Control is
dedicated to this subject.
However, many of these treatments may also act as elicitors of
enhanced resistance responses in harvested fruits and vegetables (Biles,
1991; Wilson et al., 1994). Fruits and vegetables may defend themselves
against pathogen attack or further colonization of the tissue by inducing
defense mechanisms in response to initial infection or to various
chemical, physical or biological elicitors. These induced defenses are
described as active mechanisms, which require host metabolism to
function (Keen, 1992). Disease occurs when a potential pathogen not only
circumvents the passive defenses, such as the structural barriers or the
preformed antimicrobial compounds of the host, but also avoids
elicitation of active defense responses in the tissues (Jackson and Taylor,
1996; Hutcheson, 1998). New approaches for controlling postharvest
diseases have been based on activation of the natural defense responses
induced by the host itself, by modulating them with suitable elicitors, as
http://arab2000.forumpro.fr