. Botany for agricultural students . Botany. POTATO BLIGHT (PHYTOPHTHORA INFESTANS) 357 scattered about like spores. When the conidia germinate, instead of producing hyphae they produce zoospores, which, after swimming about for a few minutes, lose their cilia and begin to produce new hyphae. If favorably located, the new hyphae find entrance to a leaf through its stomata and start the disease anew. The oogonia and antheridia resemble those of Saprolegnia, but are produced on short hyphae within the tissues of the host. The oospore has a heavy wall and is not liberated until the tissues of the
. Botany for agricultural students . Botany. POTATO BLIGHT (PHYTOPHTHORA INFESTANS) 357 scattered about like spores. When the conidia germinate, instead of producing hyphae they produce zoospores, which, after swimming about for a few minutes, lose their cilia and begin to produce new hyphae. If favorably located, the new hyphae find entrance to a leaf through its stomata and start the disease anew. The oogonia and antheridia resemble those of Saprolegnia, but are produced on short hyphae within the tissues of the host. The oospore has a heavy wall and is not liberated until the tissues of the host surrounding it decay. ' The oospores are well fitted to endure winter condi- tions, and as the dead leaves are scattered, the oospores con- tained are also scattered, and when freed it is probable that they often start the disease the following year. Potato Blight! (Phytophthora infestans). — This Fungus, com- monly called the Late Blight of the Potato, is a near relative of the Grape Mildew. It attacks the leaves, stems, and tubers of the Irish Potato and is very rapid and destructive in its work. Figure 309 shows the leaves of a Potato plant affected with this disease. Like the Grape Mildew, after the myceUum is well established in the host, conidiophores are produced (Fig. 310). The conidia may grow directly into hyphae or produce zoospores {Fig. 311). 1 Late Blight and Rot of Potatoes. Circular 19, Cornell University Agr. Exp. Sta. Investigations of the Potato Fungus, Phytophthora Infestans. Bulletin 168, Vermont Agri. Exp. Sta. Germination and Infection with the Fungus of the Late Blight of Potato. Research Bvllelin 37, "Wisconsin Agr. Exp. Sta., 1915. Studies of the Genus Phytophthora. Vol. 8, No. 7, pp. 233-276, Jour Agr. Research, U. S. Dept. Agr., Fig. 308. — Reproduction in the Downy Mildew of the Grape, a, conidiophores bearing conidiospores on the ends of their branches; 6, conidiospores; c, oospore; z, zo- ospore. Much enlarged. From Farmer's
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1919
