© Epoch ・・・ 6 ・・・ 23 ・・・ 158 ・・・ 23 ・・・ 51 ・・・ 3. Title: 2016101 Created Date: 10/4/2016 4:37:03 PM.
![]() Abstract![]()
Infection by Synchytrium endobioticum is dependent on the presence of particular varieties of its host and on environmental conditions in general favorable to vigorous growth of the potato plant. Germination of both resting and soral sporangia occurs in water, and there is an indispensable minimum of water for the distribution of the motile cells. If the soil-moisture content does not at any time reach saturation, germination is prevented, but if it is constantly near saturation, infection is repressed, probably through the reaction on the host. The most favorable condition is periodic flooding, followed by drainage and aëration. Infection may occur, if the temperature is favorable, in soil that is wet at insufficient intervals to afford a normal crop. The complete thermal range for germination of resting sporangia was not determined, but infection resulted when they germinated between 10° and 28° C. Infection from germinating soral sporangia occurred between nearly o° and 3° C. When the soil temperature was constantly maintained, infection was limited to the range 12° to 24° C., but with variable soil temperature, as in the field, infection occurs when the mean is about 21°, though the upper range may be as high as 3° C.The most favorable soil reaction is from neutral to slightly acid, the range being from about pH 3.9 to pH 8.5. The potato tolerates somewhat greater alkalinity but with reduction of yield and injury from other diseases. Although the wart fungus and the potato plant have similar requirements as to environmental factors, the disease can not spread widely under an effective quarantine on the movement of infected seed. Its controllability through the use of immune varieties reduces it, in the United States, to a problem for which the solution is at hand.
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