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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
4 Postharvest Diseases of Fruits and Vegetables
the presence of many important airborne fungi such as species of
Cladosporium, Alternaria, Stemphylium, Penicillium, Aspergillus,
Rhizopus, Mucor, Botrytis, Fusarium and others. Many of the airborne
fungi are among the most important decay agents which affect harvested
fruits and vegetables and, given the right conditions, develop and cause
decay.
Many postharvest pathogens perpetuate on crop debris in the field and
can, under suitable conditions, develop and produce abundant new
spores. These fungal spores are easily carried by air currents, winds and
rain, or dispersed by insects, to the flowers and the young fruits, at
various stages of development, and form a potential source of infection.
Soil, irrigation water and plant debris form an important source of
infection of various vegetables. Soil-residing fungi and bacteria can
attack the bulb, tuber, root and other vegetal parts, while these are still
attached to the parent plant, through a tight contact with the soil, by
lifting of soil particles by winds, rains or irrigation, through growth, or by
arriving in storage with soil residues attached to the vegetable. Some soil
microorganisms, such as species of the fungi Botrytis, Sclerotinia and
Fusarium or the bacterium Erwinia carotovora, are among the main
decay agents in stored vegetables. Host infection can occur preharvest,
during harvest or during any of the postharvest handling stages.
Harvesting instruments, containers, packing houses with their
installations, the hands of the packers or selectors, the atmosphere of the
storage rooms - are all bountiful sources of fungal spores.
Despite the diversity of microorganisms that the fruits and vegetables
carry with them into storage, only a few species can naturally attack
them, while other species that reside on the surface, at times in large
quantities, will not penetrate and will not cause any decay. The
development of disease during storage depends, primarily, on the
existence of the appropriate microorganisms alongside a given host.
However, in order for the fungal spores or bacterial cells that have
reached the suitable host to be capable of infecting, they have to
encounter the appropriate conditions for germination on the surface of
the host, to penetrate into the host tissues and to develop there.
C. SPORE GERMINATION
Spore germination is a preliminary stage to fungal penetration into
the host. The right environmental temperature, available water or
http://arab2000.forumpro.fr