Postharvest fruit rots of kiwifruit (Actinidia deliciosa) in Korea

Abstract

The overall disease incidence of postharvest fruit rots of kiwifruit (Actinidia deliciosa) in Korea averaged 32%, but the incidence ranged from 5% to 68% in the orchards surveyed. The percentage of kiwifruit showing internal and external symptoms were 21.9% and 4.9%, respectively, and an additional 5.2% of the kiwifruit showed both internal and external symptoms. Botryosphaeria dothidea and Diaporthe actinidiae cause ripe rot and stem-end rot, respectively, and were identified as the major postharvest pathogens with average isolation rates of 83.3% and 11.9%. Incidence of the postharvest fruit rots was closely correlated with ripening temperatures favourable to the mycelial growth of the major pathogens. Postharvest fruit rots occurred at all ripening temperatures 11°C and maximum disease incidence was observed at 29°C. No mycelial growth of B. dothidea and D. actinidiae occurred on potato dextrose agar plates under 11°C and the optimum temperature ranges for mycelial growth of the pathogens were 26-35°C and 26-29°C, respectively. The optimum kiwifruit ripening conditions for minimising damage from the postharvest fruit rots were a 20-day ripening at 17°C. Intensive application of fungicides just before or after the rainy season is conducted to control postharvest fruit rots in kiwifruit orchards of Korea. Benomyl WP and thiophanate-methyl WP, registered as preventive fungicides against postharvest fruit rots, are usually applied 5-6 times at 10-day intervals beginning in early June in the kiwifruit orchards. Tebuconazole WP, iprodione WP, and flusilazole WP were selected as alternative fungicides to prevent emergence of fungicide-resistant strains and reduce the number of fungicide applications. The optimum spray programme for controlling postharvest fruit rots was four applications at 10-day intervals from mid June for tebuconazole WP, iprodione WP, and flusilazole WP, compared with five applications for benomyl WP and thiophanate-methyl WP.

Extension of Shelf-life by Limited Duration of Propylene and 1-MCP Treatments in Three Kiwifruit Cultivars

“…Another limiting factor in the postharvest storage of kiwifruit is the incidence of fruit rot caused by fungi at temperatures above 20°C (Kinugawa, 2000;Koh et al, 2005;Yano and Hasegawa, 1993). Koh et al (2005) attributed the prevalence of 'Hayward' kiwifruit rot to fungi such as Phomopsis sp., Botryosphaeria sp., and Diaporthe sp. and deduced that, for kiwifruit stored at 17°C-29°C, about 20% to 95% of fruit developed rot symptoms after 20 days of storage.…”

Fungal Infection Occurrence on New Cultivars of Kiwifruit Correlated with Fruit Soluble Solids Content and Firmness

“…is a deciduous vine fruit tree cultivated in New Zealand, Italy, China and Korea (Koh et al, 2005;Luongo et al, 2011). Kiwifruit is classified as A. deliciosa (Green-fleshed kiwifruit) and A. chinensis (Yellow-fleshed kiwifruit), depending on flesh color and the existence of hair (Montefiori et al, 2009).…”

“…On average, the incidence of postharvest diseases in percentage terms was 32%, while internal and external symptoms were 21.9% and 4.9%, respectively. Additionally, both symptoms affected 5.2% of the kiwifruit crop in South Korea (Koh et al, 2005). The kiwifruit output of other countries is much superior to that of South Korea, and therefore the international competitiveness of the kiwifruit industry is important (Cho et al, 2011).…”

“…Postharvest fruit rot diseases accelerate as ethylene is secreted during ripening, the sugar content is higher and latent pathogens generate postharvest disease (Koh et al, 2005). For example, in New Zealand, the three-major postharvest fruit rot diseases of A. deliciosa are: 'Field rot' caused by Sclerotinia sclerotiorum; 'Storage rot' caused by Botrytis cinerea; and 'Ripe rot' which is caused by Botryosphaeria dothidea (Pennycook, 1985).…”

“…In the United States, postharvest diseases observed in kiwifruit are 'Botrytis rot' caused by B. cinerea, 'Alternaria rot' due to A. alternata, 'Phomopsis stem-end rot' caused by Diaporthe Actinidia and 'Blue mold' which is blamed on Penicillium expansum (Sommer et al, 1983). Postharvest fruit rot diseases reported in South Korea are 'Ripe rot', 'Stem-end rot' and 'Gray mold'; their respective generated ratios of infection are 83.3%, 11.9% and 1.4%, respectively (Koh et al, 2005). Recently, 'Sclerotinia rot' caused by S. sclerotiorum (Lee et al, 2015), and 'Black rot' caused by Nigrosporea sp.…”