Crown-Gall of Alfalfa
Introduction The crown-gall of alfalfa has been known in the United States for only a few years, the first published record of its occurrence in this country being in i909. It was at that time observed in California by SMITH (32). Since then it has been reported from Arizona (23), Oregon (26), and Utah (27). It is probable that it also occurs in other western states. The disease has been known somewhat longer in other countries. PATOUILLARD and VON LAGERHEIM (28) in I895 published the earliest
... ished the earliest record of its occurrence in connection with an outbreak in Ecuador. In I902 MAGNUS (2i) described the general features of the disease and recorded its presence in Germany. It has also been reported from England (29), and Italy, Sweden, and Switzerland (io). The lack of detailed information makes it difficult to estimate the economic importance of the disease. Old and powerful stands were killed in the fields of Ecuador (ig). MAGNUS considered the disease serious at Colmar in Alsace. SALMON (29) advised strict precautions against its spread in England. In the United States MCCALLUM (23) reported the disease as serious but not widely distributed in Arizona at the time of his observations. SMITH noted it in only a few counties of California. According to O'GARA (26), many plants two to seven years of age were destroyed by the parasite in Oregon. In I9I5 resolutions were adopted by the American Phytopathological Society (3i) recognizing the serious possibilities of the disease and recommending its investigation by the government. It is the purpose of this study to contribute to our knowledge of the life history of the causal organism. Material and methods Infected plants were secured from the vicinity of Medford, Oregon. In the winter of I9I3-I9I4 P. J. O'GARA sent specimens, 5I] [Botanical Gazette, vol. 70 This content downloaded from 080.082.and in the fall of the year I9I4 material was received from Dr. M. P. HENDERSON. Other material was secured from alfalfa plants grown and infected in the greenhouse. Standard histological and cytological methods were employed for the examination of the material; reference to these will be made in connection with various phases of the observations. Observations In I902 MAGNUS (2i) described the galls as branching tuberculate structures on the larger secondary roots of Medicago saliva. Upon examining cross-sections of the galls, he found large brown regions of irregular form, which proved to be cavities filled with resting spores of the parasite. "Thick-walled strongly encysted mycelium" was found in many of the cavities, but he did not find that the resting spores were attached to the hyphae. .The amount of mycelium present in the different cavities varied; it was often entirely lacking. The hyphae were described as continuous or branched, and the protoplasm of the host cells was often completely displaced by these "wandering hyphae." MAGNUS thought that this mycelium might " awake to new life " after the winter resting period. He described the resting spores as spherical with one side flattened; he noted a colorless hyaline cell attached to the flattened side by means of a hyaline process. Many pores were found in the centers of the flattened walls of the spores. No other stages in the life of the parasite were mentioned by MAGNUS, and not all those described were figured. So far as the writer has been able to learn, no subsequent work has been published touching upon the life history of this organism, which has been classified as Urophlyctis alfalfa ( von Lagerheim) Magnus. Figures of the galls have been published by various writers (13, 22), and all agree with MAGNUS' original description. The alfalfa plants which furnished the material for these observations were several years old. Numerous galls corresponding to the structures described by MAGNUS and others as the crowngall of alfalfa were found upon the plants (fig. i). Free-hand sections of such galls upon microscopic examination revealed numerous brownish resting spores, like those figured by MAGNUS, This content downloaded from 080.082.