Articles
Drying leaves suppresses cucurbit downy mildew caused by Pseudoperonospora cubensis
Article number
1378_25
Pages
183 – 188
Language
English
Abstract
Pseudoperonospora cubensis causes downy mildew and severe yield loss in cucurbitaceous plant species worldwide.
After entering through the stoma, it produces lesions on leaves.
Subsequently, sporangia formed on the lesions constitute a major cause of disease transmission.
Leaf wetness is necessary for germination of sporangia and encysted zoospores, and for host plant infection.
The necessary wetness duration for infection at different temperatures was elucidated previously.
For the present study, we investigated disease suppression by drying the leaves, thereby interrupting the infectious behavior of the pathogen.
After the cucumber plants were inoculated at 15 and 25°C by spraying a sporangial suspension, they were kept wet for 1-3 h.
The leaves were dried for 1 h and were rewetted for 24 h.
As a control treatment, inoculated cucumber plants were kept wet for 24 h.
The lesions on the leaves were counted 7 days after inoculation.
At 25°C, very few lesions were observed when the wetness durations before drying were 1 and 2 h.
The lesions were more numerous at 3 h wetness duration, but were fewer than those of the control treatment.
At 15°C, the lesions in all drying treatments were very few: significantly fewer than those of the control treatment.
These results indicate that P. cubensis is inactivated irreversibly by drying leaves before complete infection.
Moreover, 1 min dryness duration was sufficient to suppress infection of the P. cubensis. These results are probably useful to control cucumber downy mildew in a greenhouse.
After entering through the stoma, it produces lesions on leaves.
Subsequently, sporangia formed on the lesions constitute a major cause of disease transmission.
Leaf wetness is necessary for germination of sporangia and encysted zoospores, and for host plant infection.
The necessary wetness duration for infection at different temperatures was elucidated previously.
For the present study, we investigated disease suppression by drying the leaves, thereby interrupting the infectious behavior of the pathogen.
After the cucumber plants were inoculated at 15 and 25°C by spraying a sporangial suspension, they were kept wet for 1-3 h.
The leaves were dried for 1 h and were rewetted for 24 h.
As a control treatment, inoculated cucumber plants were kept wet for 24 h.
The lesions on the leaves were counted 7 days after inoculation.
At 25°C, very few lesions were observed when the wetness durations before drying were 1 and 2 h.
The lesions were more numerous at 3 h wetness duration, but were fewer than those of the control treatment.
At 15°C, the lesions in all drying treatments were very few: significantly fewer than those of the control treatment.
These results indicate that P. cubensis is inactivated irreversibly by drying leaves before complete infection.
Moreover, 1 min dryness duration was sufficient to suppress infection of the P. cubensis. These results are probably useful to control cucumber downy mildew in a greenhouse.
Authors
N. Nagahama, T. Usami
Keywords
Cucumis sativus, cucurbit, disease control, environmental factor, leaf wetness, plant disease
Online Articles (56)