Study In Cereal Rusts PDF Download

Excerpt from A Study in Cereal Rusts; Physiological Races: A Thesis Submitted to the Faculty of the Graduate School of the University of Minnesota Cereal rusts were known as destructive plant pests by the ancients. Observations were made on the effect of weather and location on their prevalence. The comparative susceptibility of the various cereals received some attention. Theophrastus speaks of the varying susceptibility of different cereals, as does Pliny, who says that barley is less likely to rust than are other grains. In modern times many observations have been made, but many of these were only incidental. Dietel (1887) calls attention to a certain amount of morphological and physiological variation in rust fungi, but does not definitely establish the fact that there are distinct biologic forms. Previous to his time Puccinia graminis Pers. was considered a single species found on cereals and various grasses. However, in 1894 Eriksson (1894-1) showed that, although the morphology of the fungus on the different cereal hosts varied but slightly, there was a distinct specialization in parasitism. He therefore divided the different species of rusts into subdivisions which he termed "formae speciales." Puccinia graminis, the only species extensively used in the present investigation, he divided into five formae speciales, two of which he mentioned as being sharply demarcated and the remainder as being probably also distinct. All of these forms of Puccinia graminis were capable of producing aecidia on various species of Berberis. It therefore occurred to Eriksson that perhaps his formae speciales would be equalized when grown upon the alternate host. This, however, he found not to be the case. He concluded that the forms were physiologically distinct even when grown upon Berberis. In fact he was led to believe that they became more firmly fixed after a period on the barberry. This discovery stimulated much research concerning the physiological relationships of the Uredineae. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works."