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ISHS Acta Horticulturae 1195: VI International Symposium on Persimmon

Evaluation of short postharvest gaseous treatments for inhibition of Alternaria black spot of persimmon 'Rojo Brillante'

Authors:   L. Palou, V. Taberner
Keywords:   Diospyros kaki Thunb., Alternaria alternata, carbon dioxide, oxygen, controlled atmosphere exposure, postharvest decay control
DOI:   10.17660/ActaHortic.2018.1195.38
Persimmon (Diospyros kaki Thunb.) is an expanding crop in Spain. The most important production area is Valncia (about 90% of total planted area) and astringent 'Rojo Brillante' is by far the most planted cultivar. An increasingly important factor limiting storability of persimmon is postharvest decay due to Alternaria black spot (ABS) caused by the pathogen Alternaria alternata. As in other EU countries, no chemical fungicides are currently approved in Spain for postharvest treatment of persimmon and alternative antifungal treatments are required. The availability of commercial facilities in persimmon packinghouses for fruit deastringency through CO2 treatments opens the door for potential application of antifungal gaseous treatments. 'Rojo Brillante' persimmons were artificially wound-inoculated with A. alternata and exposed 24 h later for 48 h to air at 20C (ambient atmosphere, control), air at 35C, 95 kPa CO2 at 20 or 35C, or 30 kPa O2 + 70 kPa CO2 at 20 or 35C, all at 90% RH. Incidence (% of infected wounds) and severity (lesion size) of ABS were evaluated after 3, 5, and 10 days of incubation at 20C and 80% RH. Another lot of treated fruit was cold-stored at 1C and 90% RH for up to 82 days and fruit quality attributes such as weight loss (WL), firmness, maturity index (MI), and peel color index (CI) were also determined on non-inoculated but treated fruit. After 10 days of incubation at 20C, none of the gaseous treatments applied at 20 or 35C significantly reduced ABS incidence and ABS severity was even higher on some gas-treated persimmons than on control fruit. After 40 days at 1C, ABS incidence was reduced by 30 to 40% on fruit treated with 95 kPa CO2 at both temperatures, but these reductions were not significant after 82 days. ABS severity on cold-stored fruit was also greater on gas-treated persimmons than on control fruit. In general, gas-treated and cold-stored persimmons, especially those treated with 95 kPa CO2, showed lower CI, higher MI and greater firmness than control fruit.

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