Agriculture Reference
In-Depth Information
Microbial losses
Botrytis causes several postharvest rots on kiwifruit ( A. deli-
ciosa ) that can persist even during cold storage at 0 C. Pick-
ing wounds are the main infection pathway for B. cinerea
(Michailides and Elmer, 2000). The fungus is mainly trans-
mitted to the fruits during harvesting through harboring
the picking wound (stem-end rot), which causes the forma-
tion of the glassy and water-soaked end. The infection can
spread within the fruit and cause complete disintegration
of the fruit or spread by contact to other fruits. Botrytis-
infected fruits generate ethylene, which causes loss of firm-
ness of other fruits, makes them susceptible to being in-
fected, and manifests the rotting. Under storage conditions
(i.e., 0 C) commonly applied in New Zealand, it takes about
4-12 weeks for fungal rot to propagate and less time if the
fruits are kept at higher temperatures. Many fungi growths
are associated with postharvest fruit rots of kiwifruit
(Pennycook, 1985). Phomopsis sp. and Botryosphaeria sp.
have been recognized as a major cause of postharvest fruit
rots of kiwifruit. B. dothidea and D. actinidiae usually cause
postharvest fruit rots during ripening, but B. cinerea can ini-
tiate gray mold during storage, even at low temperatures.
Koh et al. (2005) have suggested four applications of tebu-
conazole WP, iprodione WP, and flusilazole WP or five
applications of benomyl WP and thiophanate-methyl WP
at 10 day intervals from mid-June (for Korean Agricul-
ture system) as the best fungicide spray program to control
postharvest fruit rots.
Sooty mold deposited by cicadas and passion vine
hopper can cause great losses (up to 7%) in certain
orchards in New Zealand. Chlorpyrifos has been used as a
ground drench to target cicada nymphs as they emerged in
early January, but the efficacy of the pesticide is in doubt
(Kiwifruit Newsletter, 2010).
Alternative orchard managements (creating unfavorable
conditions for conidial germination through canopy man-
agement; good orchard hygiene and handling of infected
leaves/trimmings; careful handling during harvest; use of
nylon mesh collection bags) can be effective in control-
ling postharvest losses. Kiwifruit curing (incubation of
the fruits at ambient temperatures for at least 2 days be-
fore packing and cold storage can reduce Botrytis caused
rotting). Biocontrol of Botrytis through the application of
yeasts (e.g., Candida sake, C. pulcherrima, Trichosporon
pullulans, Bacillus subtilis, Pseudomonas syringae, Acre-
monium breve ,and Cryptococcus laurenti ); use of chitosan-
based coatings; and hot-water dip or incubation at 10 C
with high humidity are each effective in reducing inci-
dence of postharvest stem-end rot in cool stored kiwifruit to
various degrees (Cheah et al., 1992; Du et al., 1997; Cook
et al., 1999; El Ghaouth et al., 2002).
Maturity losses
Owing to the high sensitivity to ethylene, kiwifruit requires
careful harvesting and postharvest handling. Common in-
dustrial practices that cause very small injuries (i.e., brush-
ing, bruising) can trigger ethylene biosynthesis and acceler-
ate the ripening process (Massantini et al., 1995; Mencarelli
et al., 1996).
Kiwifruit softening is generally set off prior to the pro-
duction of ethylene; carbohydrates start degrading and
pectin deesterification occurs together with an increase
in pectinesterase activity (MacRae and Redgwell, 1992).
Ethylene, however, stimulates the activity of pectinesterase
(Wegrzyn and MacRae, 1992), leading to higher kiwifruit
softening rates. Short-term N 2 treatment (Song et al., 2009)
and the use of salicylic acid (Zhang et al., 2003) can in-
hibit cell wall degrading enzymes such as polygalactur-
onase, lipoxygenase, cellulase, and pectinemethylesterase
and maintain the firmness of kiwifruit. The application of
1-methylcyclopropene (1-MCP) (Boquete et al., 2004) and
use of controlled atmosphere (2% O 2 +
5% CO 2 ) and ultra-
low oxygen environment (0.7% O 2 +
0.7% CO 2 or 1% O 2
+
1% CO 2 ) (Antunes and Sfakiotakis, 2002a) are success-
ful in suppressing ethylene production during storage and
extending the storage life. However, low oxygen stored
kiwifruit cannot sustain natural ripening at room tempera-
ture (20 C) due to the 1-aminocyclopropane-1-carboxylic
acid concentrations in the tissue and the ripening pro-
cess requires initiation by propylene treatment (Thomai
and Sfakiotakis, 1997; Antunes and Sfakiotakis, 2002a).
Ultra-low oxygen storage conditions can induce a long de-
lay period even with propylene treatment (Stavroulakis and
Sfakiotakis, 1997; Thomai and Sfakiotakis, 1997; Antunes
and Sfakiotakis, 2002a).
Other defects
Storage atmospheres containing high CO 2 (
>
8%) and low
O 2 (
3%) can induce abnormal metabolism and cause sev-
eral defects such as the formation of hard core, loss of nor-
mal flavor, flesh breakdown, and formation of off flavors
(Harman and McDonald, 1989). Moisture loss of kiwifruit
during long-term storage/shipment can lead to significant
losses in yield and poor appearance of the fruits. The use
of calcium caseinate, chitosan, PrimaFresh 50-V, and Sem-
perfresh edible coatings has been proven to be effective in
reducing moisture loss without compromising the ripening
of hardy kiwifruit (Fisk et al., 2008).
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