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Taiwan Agricultural Research Institute, Council of Agriculture, Executive Yuan--Publication-Special Publication of TARI-No.184

No.184

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Pathogen Identification and Management of Flower and Fruit Wet Rot of pitaya (Hylocereus spp.) Caused by Gilbertella persicaria var. pitaya

Pathogen Identification and Management of Flower and Fruit Wet Rot of pitaya (Hylocereus spp.) Caused by Gilbertella persicaria var. pitaya

Lin, C. P.1, *, Tsai, J. N.1, Ann, P. J.1, Chen, P. R.1, Chang, J. T.1 and Hsu, T. H.1

Abstract

    Pitaya (Hylocereus spp.) is one of the important newly emerging fruit crops in Taiwan. Fruit wet rot, a severe postharvest disease of pitaya caused by Gilbertella persicaria var. pitaya, was first found in August 2009. Fruit infection occurred in the field during rainy season with a small water-soaked lesion around the stem-end, which developed into fruit soft rot within 3-5 days after harvest. Occasionally, fruit soft rot initiated from lesions on fruit skin or scales, and internal black rot of fruit were also observed. Results of survey of pitaya orchards showed that infection of G. persicaria var. pitaya on young fruits or on flower buds and petals resulted in the development of symptoms similar to that observed in the postharvest fruits. Most of the infected fruits in the orchard failed to develop normally and dropped prematurely. However, in regards of the differences of the number of splitted sporangial wall, ITS sequence and virulence to fruits of pitaya, the G. persicaria var. pitaya was different from the holotype of G. persicaria. Brown to black sporangia of G. persicaria var. pitaya were formed on the surface of infected tissues, especially under humid conditions. Our data showed that tissue wounding was an important factor affecting the disease severity. G. persicaira var. pitaya were pathogenic on unwounded fruits of peach and guava, and wounded fruits of apple, mango, persimmon, plum, wax apple and tomato, but they were non-pathogenic on starfruit, melon, banana and kiwifruits. The results of chemical selection showed that cyprodinil + fludinoxonil, pyraclostrobin, prochloraz-Mn, tridemorph, difenoconazole and tebuconazole, fluazinam were the potential fungicides for controlling the disease. As for organic farming, the data showed that Bordeaux mixture and both cinnamon oil products, - Hey-Show-Lo and Tan-Wu-Zung- could inhibit mycelial growth and sporangiospores germination well. To control the disease, apply mycelial-growth- inhibiting chemicals the before raining to protect the fallowers and young fruits from infection and sporangiospores-germination- inhibiting chemicals after raining to treat the infected tissues. The infected tissues should be excised out of the orchards immediately therefore avoiding further infection of the fruiting fruits or other tissues. Also, harvest in the raining day should be avoided to reduce the infection rate during storage.


1 Plant Pathology Division, Taiwan Agricultural Research Institute, COA
*Corresponding Author,E-mail: cplin@tari.gov.tw; FAX: +886-4-23302803

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