A CONTRIBUTION TO THE LIFE HISTORY OF 

 SPONGOSPORA SUBTERRANEA 



[a preliminary report] 



By L. O. KuNKEL, 



Pathologist, Office of Cotton- and Truck-Disease Investigations, 



Bureau of Plant Industry 



INTRODUCTION 



The manner of infection of tubers of the potato (Solanum tuberosum) 

 by Spongospora subterranea seems never to have been observed. Osbom 

 (14) ^ has described and figured what he considers a single amoeba in a 

 potato cell, but as will be seen from the writer's descriptions this can not 

 be regarded as a significant step in the process of infection. It has 

 usually been assumed that each potato cell becomes parasitized by one, 

 or at most only a very few, amoebae in much the same way as suggested 

 by Woronin (17) for cabbage cells attacked by Plasmodiophora brassicae. 



Spongospora subterranea was first technically described by Wallroth (16) 

 in 1842 as Erysibe subterranea. Although it seems to have been widely 

 distributed in Europe, it received little attention until 1885, when Brun- 

 chorst (2), a Norwegian botanist, made a careful study of the disease. 

 His observation of plasmodia in the potato cells led him to place it in the 

 group of the Plasmodiophoraceae. It was his opinion that the organism 

 could live saprophytically in the soil, and he states that it is a general 

 belief among farmers that lime and excess moisture favor the disease. 



In 1892 Von Lagerheim (9) reported 5. subterranea as very generally 

 distributed in Quito, South America, which is the native habitat of the 

 potato and may also be the home of Spongospora. 



Johnson (7) studied the germination of the spores and describes eight 

 swarm spores coming from each cell of the spore ball. In stained prepara- 

 tions he thought that he was able to see approximately eight nuclei in 

 some of the ungerminated spores. Johnson did not observe the way in 

 which infection takes place, but suggests that the swarm spores find their 

 way into the tuber through lenticels, sprouts, and wounds. 



Massee (10) published an account of the disease in 1908. According 

 to his description (11), which is very brief, the spores are uninucleate and 

 on germination produce only one amoeba. He did not observe infection, 

 but thinks that the amoebae may be able to infect new cells by passing 

 through the pits present in the cell wall. 



' Reference is made by number to " Literature cited, " p. 278. 



Journal of Agricultural Research, Vol. IV, No. 3 



Dept. of Agriculture, Washington, D. C. June 15, 1915 



(265) 



G— 49 



