The pomegranate extract proved to be very effective as
preventive treatments in all tested host/pathogen combinations.
The development of rots caused by P. digitatum and P. italicum on
lemons and P. digitatum on grapefruits was completely inhibited by
PGE applied at 12 g/l (Fig. 4), and fruits remained healthy up to the
end of the experiment (data not shown). At the same concentration
the incidence of P. expansum rot on apples was reduced by 80.0%
(Fig. 4). Significant reductions of the incidence of rots were also
obtained for lower concentrations of PGE (1.2 and 0.12 g/l). In
particular, P. italicum was completely inhibited or was reduced by
80.1% on lemons treated with PGE at 1.2 and 0.12 g/l, respectively.
On the same host, P. digitatum infection was reduced by 85.8%
(1.2 g/l PGE) and 28.5% (0.12 g/l PGE), while on grapefruits the
incidence of rots was reduced by 38.5 and 23% with PGE at 1.2 and
0.12 g/l, respectively. A lower efficacy was observed with PGE at
1.2 and 0.12 g/l against P. expansum on apples as it was reduced by
only 31.1 and 6.7%, respectively (Fig. 4). Data about the severity of
the disease (diameter of lesions) were almost always in agreement
with those of the incidence of the disease (percentage of infected
wounds).
In trials conducted on lemons with P. digitatum and P. italicum a
high efficacy was obtained also when the pathogen was inoculated
12 and 24 h after PGE application (Fig. 5A and B). In both
inoculation times, both pathogens were completely inhibited by
PGE at 12 and 1.2 g/l and a significant reduction of incidence and
diameter of rots was evident with PGE at 0.12 g/l.
In all trials, fruit treated with PGE did not show any
modification of color or morphology which may be indicative of
phytotoxicity