SPIECKERMANN S GERMAN POTATO DISEASE. 



I6 7 



eyes which will not germinate. .Sometimes four weeks after planting one finds such tubers 

 externally sound but with black eyes, and on cutting them discovers that the vascular ring is 

 wholly destroyed. Even in these, if there is no mixed infection, the vascular ring is not 

 decidedly blackened. But even if the tubers are planted with sound eyes and show only 

 small rot-spots, many of them die, while others yield sound plants. 



If the discoveries of this summer are confirmed, this fact constitutes an important 

 difference between this disease and Appel's ring disease. 



We may now inquire whether the bacteria found in the diseased plants are the cause 

 of the disease. 



In 1909, with these bacteria, numerous inoculations were made in wounds, in stems 

 above ground, and in plants standing in the field, and almost all of these were successful, the 

 diseased phenomena being produced both on the parts above ground and in the tubers. 

 There is, therefore, no doubt as to the causal relation of the bacteria to the disease. A spe- 

 cial predisposition, other than the existence of wounds reaching to the vessels, is not neces- 

 sary. Also, no difference in varieties has been observed up to this time. They infected 

 without difficulty Abdul Hamid, Hilde, Iris, Caecilie, Bonar, Professor Maercker, Norma, 

 Busola, Topas, Zlozien, and Roland. Spontaneous outbreaks have been observed in the 

 fields thus far only on Professor Maercker. 



The organism is unlike that of Appel's ring disease, and Dr. Appel has himself con- 

 firmed this during a visit. 



Spieckermann gives the following description of his organism: 



They are very short, non-motile rods 0.5 to 0.7^ long, which grow very slowly on all artificial 

 substrata. In peptonized meat-water agar and on potato they produce in the course of several weeks 

 white, pale yellow to dark yellow slimy-flowing or viscid (fadenziehende) zoogloeae. Gelatin is not 

 liquefied. They grow distinctly in gelatin stabs, but without distinguishing phenomena, the surface 

 growth being slight (fehlt so gut wie ganz). On gelatin and agar plates they grow as very small, 

 round, non-characteristic colonies which are first visible to the naked eye after about 8 days ; some of 

 these are viscid and stick to the needle. Meat peptone-bouillon is well clouded (starkgetriibt). In 

 substrata containing sugar there is no fermentation. Milk after several weeks coagulates slowly and 

 there is a gradual solution of the casein. The serum is colored yellow, smells like milk changed by the 

 peptonizing steam-resistant (Kochfest) bacteria of milk, and is in most of the strains viscid (fadenzie- 

 hend). The optimum temperature is under 30 C. Spore-formation has never been observed. The 

 rods are Gram positive. 



Mr. Kotthoff was associated with Spieckermann in these studies. 



On asking Dr. Spieckermann for further information he replied that a full paper on 

 this disease is in press in Berlin (Landw.-Jahrb.) and may be expected about the middle 

 of 1 91 4. From his reply I judge that while the disease occurs in Westphalia principally 

 on potatoes, he has also seen it on tomatoes, and this further confirms my belief in the 

 identity of the two diseases. He says the organism is quite distinct from Bad. 

 solanacearum. 



LITERATURE. 



1910. 



1911 



Spieckermann, A. Uebereine noch nicht bes- 

 chriebene bakterielle Gefasserkrankung der 

 Kartoffelpflanze. [Vorlaufige Mitteilung.] 

 Centralb. f. Bakt., 2te Abt 27 Bd., Jena, 

 June 1, 1910, pp. 205-208. 



Spieckermann, A. Beitrage zur Kenntnis der 

 Bakterienring und Blattrollkrankheiten der 



Kartoffelpflanzen. Jahresberieht der Verein- 

 igung fur angewandte Botanik. 8 Jahrg. 

 1910. Berlin, 191 1, pp. 1-19. 



The preceding appears to be the earlier publication. This 

 one gives numerous analyses showing dry substance in sound 

 and diseased tubers, stems, etc. An average of 20 analyses of 

 diseased control tubers gives 22.55 Per cent of dry substance; 

 an average of 13 sound controls gives 24.60 per cent. 



