. Corn smut caused by Ustilago maydis. Corn; Smut diseases. Fig. 2. Diagram illustrating the life cycle of Vslilago maydis. There are many types of deviation from the one given, especially in germination of chlamydospores and mei- osis (by C. M. Christensen). nothing about nuclear condition, mode of formation, nature of germination, or function in the life cycle. The smutty overgrowth produced by U. maydis on corn (Z. mays L.) and teosinte (E. mexicana Schrad.) has been called by several common names: boil, blister, excrescence, gall, pustule tumor, sorus. and swelling. Until about 1900. the t
. Corn smut caused by Ustilago maydis. Corn; Smut diseases. Fig. 2. Diagram illustrating the life cycle of Vslilago maydis. There are many types of deviation from the one given, especially in germination of chlamydospores and mei- osis (by C. M. Christensen). nothing about nuclear condition, mode of formation, nature of germination, or function in the life cycle. The smutty overgrowth produced by U. maydis on corn (Z. mays L.) and teosinte (E. mexicana Schrad.) has been called by several common names: boil, blister, excrescence, gall, pustule tumor, sorus. and swelling. Until about 1900. the term pustule was not uncommon in the and blister is still commonly used in certain European countries (237). Although boil is still used frequently, the term gall is used most com- monly, particularly in the Life History.—The life cycle of U. maydis is com- pleted in most cases every time it passes through the host. Three distinct nuclear phases occur in the life history of U. maydis: the diplophase. haplophase, and dicaryophase. This involves karyogamy. meiosis, and plasmogamy. Consequently, a collection of chlamydo- spores does not represent a pure breeding population. The diploid stage is normally restricted to the mature chlamvdospore and ends when the spore germinates (Fig. 2). Chlamydospores are produced in vast numbers in smut galls on corn and teosinte. The spores overwinter on the ground, especially in galls and in plant parts. The smut galls are more or less repellent to water; therefore, the chlamydospores may appear perfectly dry in the spring although the gall may be lying on wet ground. Of course, this may not necessarily occur in moist and humid regions. The galls, at least the greater portion of them, persist until the crop is harvested. Some galls are broken off by mechanical means and fall to the ground; and chlamydospores may be washed off by rain, scattered by farm machinery. perhaps by insects, and readily by wind. Usually, the diploid chlamv
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