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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
48 Postharvest Diseases of Fruits and Vegetables
exposed to lower, more typical degreening concentrations (0.002 ml l-i).
Furthermore, the addition of commercial or partially purified
preparations of the abscission enzymes to abscission areas of debuttoned
oranges, before inoculation with D. natalensis, caused a significant
increase in stem-end rot development.
Another way to study the relationship between ethylene-dependent
abscission enzymes and the susceptibility of the fruit to stem-end rot was
the use of metabolic inhibitors that reduce enzyme activity during
high-ethylene treatment (Brown, G.E. and Burns, 1998). When citrus
fruits were dipped before degreening in 2,4 dichlorophenoxyacetic acid
(2,4-D), which is known to reduce PG and Cx activity (Riov, 1974) or
silver thiosulfate, which is an inhibitor of ethylene action (Veen, 1983),
they showed enhanced resistance to stem-end rot when inoculated after
degreening (Fig. 10).
•o
CD
I
E
d)
(/)
CO
JO
Q.
80
60
40
S- 20
b
4-
Control
•
2,4-D
-^-
STS
—B—
\ 1 ^
6 10
14
Days (300C)
Fig. 10. Incidence of stem-end rot in Valencia oranges dipped in water (control),
2,4-dichloro-phenoxyacetic acid (2,4-D), or silver thiosulfate (STS) before
degreening with 0.055 ml l-i of ethylene for 42h. Debuttoned fruit were
inoculated with Diplodia natalensis mycelium after ethylene treatment. Bars
represent standard deviation. (Reproduced from Brown and Burns, 1998 with
permission of Elsevier Science).
http://arab2000.forumpro.fr