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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
304 Postharvest Diseases of Fruits and Vegetables
Penicillium, Alternaria and Cladosporium are more common in plums
and cherries, while Rhizopus causes heavy losses mainly in peaches,
nectarines and apricots.
A. Monilinia spp.
Three species of Monilinia are involved in brown rot of stone fruits:
M fructicola (Wint.) Honey, M fructigena (Aderh. & Ruhl.) Honey and
M laxa (Aderh. & Ruhl.) Honey.
Brown rot is of major importance in stone fruits in many countries
and, if the weather is wet and cool in the spring, it can attain epidemic
levels in peaches, nectarines and apricots (Holz et al., 1998). There are,
however, differences in the geographical distributions of the three
Monilinia species. While M laxa is a serious problem in apricots in the
United States, it may attack all stone fruits to some extent in Chile and
South Africa (Eckert and Ogawa, 1988). Monilinia fructicola is a most
important pathogen in the Americas, South Africa, Japan, Australia and
New Zealand, while M fructigena is a common pathogen in some stone
fruits in Europe and Asia, but not in the United States (Snowdon, 1990).
The fungi survive the winter as mycelium in rotted or mummified
fruits in the orchard. In wet weather, abundant conidia are produced and
are spread in the orchard by rain splash and wind (Tate and Corbin,
1978) or by insects. In addition to the asexual conidia, M fructicola
frequently produces stromata (sclerotial mat or resistant fungal tissue),
that give rise to the sexual state - apothecia with ascospores (Biggs and
Northover, 1985; Willetts and Hadara, 1984). In other species of
Monilinia apothecial production is rare (Willetts and Hadara, 1984).
Examining the conditions under which M /rwc^jco/a-infected fruit
develop stromata and produce apothecia, Holz et al. (1998) found that
apothecia were formed only from infected fruits that had been subjected
to a drying and cold temperature incubation, during which a
stromatization process takes place. In the orchard, apothecia are formed
during the bloom, from mummies that have survived the winter. They
commonly appear on orchard floors with natural vegetation or cover
crops, which may create a habitat that reduces desiccation. Apothecial
production has not been observed in infected fruits which are attached to
trees, but only in those lying on moist soils (Hong et al., 1996; Willetts
and Hadara, 1984). Liberated ascospores may serve as a major source of
primary inoculum for initiating infection of blossoms (Hong et al., 1996).
The optimal temperature for daily discharge of ascospores from the
apothecia is IS^'C, although high discharge can occur at any temperature
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