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Abstract:
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Despite the importance of calcium content and the effects of calcium
applications in many fruit species, no clear relationship between fruit Ca content
and early softening is established in kiwifruit. Diverse results have been reported
with Ca applications in kiwifruit, particularly regarding fruit firmness. Thus,
experiments were undertaken to define the influence of fruit Ca status and Ca
applications on kiwifruit quality, with an emphasis on fruit softening in cold storage.
Fruit samples from the major kiwifruit cultivation areas in Chile were analysed for
Ca content in two seasons, and related to the time required for the fruit to soften to
18N when maintained at 0°C and 90% RH. Although the time to reach 18N varied
widely, no significant relationship was established, suggesting that additional factors
to Ca content are relevant in determining softening susceptibility. During two
seasons Ca was applied to fruit by spraying vines (fruit), and by postharvest dipping.
In 2003/2004, CaCl2 was applied by spraying in 2 orchards at 0.8% commercial
product (1700 ppm Ca), during fruit development (9 and 17 applications), or by one
postharvest dip treatment with 2% of CaCl2 (4250 ppm Ca). In vines sprayed
17 times, fruit Ca content was higher, and storage life 50–80% greater, than fruit
from vines sprayed 9 times and in fruit from control vines. In 2004/2005, 600 ppm
Ca was applied 4 times preharvest using 3 commercially-available sources (plus, one
water-applied control). In a different experiment, the same sources of Ca at
2000 ppm were applied as postharvest dips. Preharvest Ca application produced
phytotoxic effects on both leaves and fruit; postharvest applications did not produce
any phytotoxicity but in both cases significantly increased storage life. Reducing the
concentration and times of Ca applications (up to 4) in 2004/2005 eliminated
phytotoxic effects, but the beneficial effects on fruit quality were reduced. |