Articles
THE EFFECT OF CALCIUM CONCENTRATION AND OSMOTIC PRESSURE OF NUTRIENT SOLUTION ON CUCUMBER DOWNY MILDEW IN A WATER CULTURE SYSTEM
Article number
548_72
Pages
581 – 590
Language
English
Abstract
The present work was conducted to study the effect of calcium (Ca) concentration and osmotic pressure of nutrient solution on the occurrence and development of cucumber downy mildew, Pseudoperonospora cubensis (Berk. & Curt.) Rost.
One susceptible ‘ Pretty ‘ and one resistant ‘ Poinsett ‘ cucumber cultivar were grown in water culture system using plastic containers with nutrient solution.
Composition of the control nutrient solution is 1 unit of Enshi-shoho (NO3-N 16, PO4-P 4, K 8, Ca 8, Mg 4 meq liter-1 ; osmotic pressure 4 X104 Pa). Three levels of Ca (Ca 16, 24 and 32 meq liter-1 ) by adding CaCl2 to the control solution and three levels of osmotic pressure (4, 6, 8 X104, respectively) by changing concentrations of total salts of the Enshi-shoho ( 1 (control), 1.5 and 2 units) were applied.
High Ca concentration increased the soluble Ca concentration and the osmotic pressure of the plant petiole sap and the total Ca content of the leaves in both cultivars.
The number of days to occurrence of the disease was longer in the resistant cultivar ‘ Poinsett ‘ than that in the susceptible one’ Pretty ‘. And that was also longer in the high osmotic pressure (8 X104 Pa) treatments, in both Ca 32 meq liter-1 and 2 units of Ensh-shoho (Ca 16 meq liter-1) than that in the control in both cultivars.
The percentage of lesion area in ‘Poinsett ‘ was significantly lower than that in ‘ Pretty ‘, and that was suppressed by high osmotic pressure treatments (8 X104 Pa), both Ca 32 meq liter-1 and 2 units of Enshi-shoho in both cultivars, while a negative correlation was found between the percentage of lesion area and the osmotic pressure of petiole sap.
These results indicate that the osmotic pressure of nutrient solution was the effective factor than the Ca concentration in the suppression of downy mildew in cucumber.
One susceptible ‘ Pretty ‘ and one resistant ‘ Poinsett ‘ cucumber cultivar were grown in water culture system using plastic containers with nutrient solution.
Composition of the control nutrient solution is 1 unit of Enshi-shoho (NO3-N 16, PO4-P 4, K 8, Ca 8, Mg 4 meq liter-1 ; osmotic pressure 4 X104 Pa). Three levels of Ca (Ca 16, 24 and 32 meq liter-1 ) by adding CaCl2 to the control solution and three levels of osmotic pressure (4, 6, 8 X104, respectively) by changing concentrations of total salts of the Enshi-shoho ( 1 (control), 1.5 and 2 units) were applied.
High Ca concentration increased the soluble Ca concentration and the osmotic pressure of the plant petiole sap and the total Ca content of the leaves in both cultivars.
The number of days to occurrence of the disease was longer in the resistant cultivar ‘ Poinsett ‘ than that in the susceptible one’ Pretty ‘. And that was also longer in the high osmotic pressure (8 X104 Pa) treatments, in both Ca 32 meq liter-1 and 2 units of Ensh-shoho (Ca 16 meq liter-1) than that in the control in both cultivars.
The percentage of lesion area in ‘Poinsett ‘ was significantly lower than that in ‘ Pretty ‘, and that was suppressed by high osmotic pressure treatments (8 X104 Pa), both Ca 32 meq liter-1 and 2 units of Enshi-shoho in both cultivars, while a negative correlation was found between the percentage of lesion area and the osmotic pressure of petiole sap.
These results indicate that the osmotic pressure of nutrient solution was the effective factor than the Ca concentration in the suppression of downy mildew in cucumber.
Authors
S. Tanaka, T. Ito, Y. Ochi, Y. Someya, T. Hirabayashi
Keywords
cucumber, downy mildew, calcium, mineral nutrition, osmotic pressure
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