Agriculture Reference
In-Depth Information
days after inoculation and fruit retention was measured up to 108 days later. The authors
proposed that ReZist and ASM reduce fruit abscission by altering endogenous hormones
levels.
Effective postharvest decay control is important for marketing fresh citrus. Field trials
were conducted between 1999 and 2003 to evaluate effects of several chemicals, includ-
ing the plant activators ASM, fosetyl-Al and phosphorous acid, on natural postharvest
infections of citrus
(Ritenour
et al.,
2004).
However, only
phosphorous acid demonstrated
signifi cant effi cacy and, in one experiment, reduced total decay by 36%.
4.2.1.6
Peach
Peach fruit usually have a very short postharvest shelf life and rely on the use of the
modifi ed atmosphere storage, refrigeration and fungicides to control postharvest disease.
Liu
et al.
(2005a,b) investigated postharvest application of ASM as a possible method to
improve resistance of 'Jiubao' peach fruit
to
P. expansum,
the causal agent of blue mould.
Harvested peaches were immersed
for
5 minutes in a solution containing 200 mg l
1
of
ASM and then air dried. Sixty hours after treatment, the fruit were wound-inoculated with
P. expansum
and then incubated at 22
o
C at high humidity. After 7 days incubation, disease
incidence on ASM-treated fruit was reduced by 50% and disease severity by 64% com-
pared with control fruit. Effects of postharvest ASM treatment on fruit quality parameters
such as taste and aroma are unknown and therefore further research is required before this
treatment could be considered for commercial production.
4.2.1.7
Melon
Foliar application of ASM (50 mg l
1
) before fl owering protected rock melons and Hami
melons against natural postharvest infection by
Alternaria
spp.,
Fusarium
spp. and
Rhizopus
spp. (Huang
et al.
, 2000). A further increase in disease resistance was achieved
when ASM-treated fruit were dipped in guazatine at harvest. Benefi ts of combining treat-
ments was also observed on fruit that were sprayed with ASM 2 weeks before harvest,
and then dipped in guazatine after harvest (Bokshi
et al.,
2006). Interestingly, postharvest
disease severity was not further reduced on fruit that had received four ASM applications
during the season. More recently, Bokshi
et al.
(2007) demonstrated that application of
ASM 2 weeks before harvest, combined with a postharvest dip in hot (55
o
C) iodine,
provided signifi cantly greater control of postharvest rots than guazatine alone. They pro-
posed that the integrated use of chemically induced resistance with hot iodine can offer
an environmentally safe alternative to the conventional fungicide dip.
Harpin was investigated as a postharvest dipping treatment to protect Hami melons
against pink rot, caused by
Tricothecium roseum
(Bi
et al.,
2005). Fruit that were half
immersed in harpin (90 mg l
1
) before inoculation expressed elevated resistance to decay
in both the treated and the untreated halves. Disease suppression was evident for 8 and
6 days in '8601', and for 5 and 3 days in 'New Queen', in treated and untreated halves,
respectively. Increasing harpin concentration to 200 mg l
1
did not further enhance dis-
ease control. More recently, full immersion of '8601', and 'New Queen' fruit in harpin
(90 mg l
1
) was shown to promote resistance to postharvest wound infections by
Alternaria alternata, Fusarium semitectum
and
T. roseum
(Yang
et al.,
2007). Decay
