IX.— The life-history and cytology of synchytrium endobioticum (schilb.), perc., the cause of wart disease in potato

Abstract

Wart disease of the potato was first reported from Hungary in 1896 by Schilberszky (43), who gave a brief description of the summer and the resting sporangia, named the organism Chrysophlyctis endobiotica , and included it in the Chytridinece . He saw the discharge of the zoospores from the summer-sporangia, and he put forward the view that the zoospores were responsible for the further distribution of the organism through the tumour by the ability which he believed they possessed of boring their way through the walls of the host cell into the adjoining cells. The fungus probably existed in England many years before Schilberszky’s paper was written, but its presence in this country was not generally recognised. In 1902 Potter (36) published a short paper on the organism. He there showed that resting sporangia, which had been kept dry during the winter, were able to cause the infection of tubers the next season. The distribution of the organism through the tumour he attributed,to its division, when in a condition which he describes as plasmodial, and to the passage of the segments so produced through the walls into the adjacent cells. For several years after Potter’s publication appeared few facts were added to the existing knowledge of the disease, but in 1907 Borthwick (4) reported that leaves could be attacked as well as tubers. In the following year, Salmon (42) carried out a series of infection experiments, from the results of which he concluded that resting sporangia, after exposure for I f hours to a temperature ranging from — 5° C. to — 6° C., could dispense with the winter dormancy and germinate at once. Shortly afterwards two notes appeared, one from the pen of Johnson (16) and the other from that of Weiss (49). Both succeeded in obtaining the germination of the resting sporangium, and, in addition, Johnson found that the zoospores liberated exhibited the usual characteristics of the Chytridian zoospore, while Weiss remarked upon the rapidity with which they became amoeboid. In December of the same year Masses (31), when exhibiting specimens of diseased tubers at a meeting of the Linnean Society, expressed the opinion that the organism belonged to the genus Synchytrium ; but he based his statement upon the so-called epidermal nature of the parasite and upon the supposed presence of an enveloping membrane round the protruding contents of the germinating resting sporangium, both of which suppositions have since been shown to be incorrect.