Journal of Taiwan Agricultural Research

Author:Junwei Fan、JyhNong Tsai、Chuping Lin*

Abstract:

Fusarium fruit rot is one of the common postharvest diseases of pitaya fruit in Taiwan. Since 2013, infected postharvest fruits were collected, exhibiting symptoms such as light brown patches with transverse stripes, white mycelium on the surface, or water-soaked lesions in severe cases. Green spots and less frequently observed scarring or rot on the pedicels and junctional branches of young fruits were also collected. All isolates obtained from these tissues exhibited morphological characteristics like those of Fusarium oxysporum. Further examination of colony morphology and sporulation patterns, combined with multilocus phylogenetic analyses based on RNA polymerase II second largest subunit (rpb2) and translation elongation factor 1-α (tef1) confirmed that all isolates belonged to F. oxysporum. Through artificial inoculation, symptoms on the postharvest fruits caused by F. oxysporum were confirmed, with symptoms showing a strong correlation with environmental humidity. When inoculation was performed on the surface of field-growing young fruits, green spots appeared after the color transition stage. Interestingly, consistent with the observations in the field, these spots did not progress to typical Fusarium fruit rot as the fruit matured, suggesting that the green spot and fruit rot symptoms may arise from infections occurring at different stages of fruit development. Also, the symptom of scarring and rot on pedicels were confirmed by the inoculation on the growing young fruits. This is the first disease report of the diversified symptoms on pitaya fruits caused by F. oxysporum, which can be attributed to different environment conditions and inoculation stage.

Key words:Pitaya, Postharvest disease, Fusarium fruit rot, Fusarium oxysporum

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