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

FREEDOM PALESTINE FREEDOM PALESTINE FREEDOM PALESTINE
Physiological and Biochemical Changes 101
TABLE 5
Ethylene production by fruit discs (3 mm^) otRhizopusinfected
'Rutgars' tomatoes and non-ripening nor tomatoes*
Tested
tissue
a
b
c
d
e
'Rutgars'
mature-green
1.2
8.1
30.2
2.0
0.0
Ethylene Production (|il kg-i h-i)
mature-green
0.4
5.8
19.9
0.0
0.2
Nor
Mature
0.3
0.5
11.2
0.3
0.0
a - healthy pulp; b - healthy pulp 1-5 cm from rotted area; c - healthy
pulp at the periphery of rot; d - rotten pulp at the periphery of the
healthy pulp; e - rotten pulp from the center of the lesion.
* Reproduced from Barkai-Golan and Kopeliovitch (1983) with
permission of the Academic Press.
Barkai-Golan et al. (1989b) studied the source of ethylene in tomatoes
inoculated with B. cinerea or Geotrichum candidum by using aminoxyacetic
acid (AOA), a potent inhibitor of plant-originating ethylene (Yang, 1985).
AOA application at the site of inoculation with B. cinerea was found to
inhibit ethylene production by 55-60% in the normal tomato fruits and by
about 80% in the non-ripening nor mutant fruits (see Figs. 21 and 22).
Since AOA acts as a specific inhibitor of ethylene biosynthesis by higher
plants, these results suggest that ethylene production in both normal
and mutant fruits is of plant origin, and is induced by the pathogen. The
inability of AOA to arrest the production of infection-ethylene totally
may be due to the short lag time between its application and the fungal
inoculation, which prevents sufficient uptake by the tissue.
The source of ethylene in the infected tissue was also studied in citrus
fruit inoculated with P. digitatum (Achilea et al., 1985a, b) which is one of
the fungi capable of producing high levels of ethylene in vitro (Hag and
Curtis, 1968). Inoculation of citrus fruit with the fungus, similarly to other
stresses, enhances the production of both ethylene and the compound ACC
(1-aminocylopropane-l- carboxylic acid), which is the precursor of ethylene
production in higher plants (Yang and Hoffman, 1984). Achilea et al.
http://arab2000.forumpro.fr