Potato Diseases at a Microscopic Level

“It is not unusual to fine a decayed spot in the center of potatoes otherwise apparently in good condition. A microscopic examination a portion of the diseased part will show that the decay commenced where the vascular bundles concentrate. At that point the air is in greater volume than elsewhere. Although these mineral acids and caustic alkalies dissolve starch granuals, they do not affect the cellulose cells which contain the starch. When such spots are exposed to the atmosphere the fungus blue-mold forms on the surface. This disease, therefore, has not relation to potato-rot, as ordinarily understood. f represents the mycelium (roots) of blue-mold, Penicillium glaucum, and G that of potato-rot, Peronospora infestans.” -Watts, 1874

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