Oct. x. I9 2o Fusarium-B light (Scab) of Wheat and Other Cereals 19 



water from the test tube evaporates or is used by the fungus. Such a 

 tube provides stem or potato plug cultures with uniform moisture for 

 four or five months without being refilled. This is as long a period of time 

 as is necessary for the formation of perithecia in any case. When stems 

 are used they can be placed directly in the test tube so as to reach the 

 bottom, but when potato plugs, bean pods, or other cultural substrata 

 are used it is better to place some cotton on the bottom of the test tube 

 so that the plugs will be just above the water level. Such test tubes are 

 handled in very much the same way as common test tubes, except that 

 more care should be taken in sterilizing them, since a sudden decrease 

 in the pressure in the sterilizer is likely to force the water out of the bulb 

 into the tube. 



PATHOGENICITY 

 PREVIOUS INVESTIGATIONS 



A large number of Fusarium species have been reported by various 

 workers as attacking the cereal crops in one way or another. In a large 

 number of cases the particular organisms have been wrongly identified 

 or not identified at all. The true relation of the various Fusarium 

 species to the different diseases on the cereal crops attributed to these 

 species is even less understood than their taxonomy. Indeed, there 

 are but few papers out of over 200 references in which proof of the 

 pathogenicity and true relation of some of these organisms to certain 

 cereal diseases is given. No papers except those most directly con- 

 nected with the problem can be mentioned here. 



Selby (9) considered Gibber ella saubinetii and its conidial form which 

 he, following Saccardo, called Fusarium roseum, as the cause of the 

 blighting of wheat heads, but he failed to produce the disease by inocu- 

 lating heads with the conidia and ascospores of this organism. In 

 1909, Selby and Manns (11) succeeded in producing blighting of wheat 

 and oat heads by spraying them during moist weather with a suspension 

 of conidia obtained by washing samples of wheat, barley, oats, emmer, 

 and spelt. In this way they thought they obtained the conidia of 

 F. roseum and its perfect form, G. saubinetii. It is very likely that it 

 was the conidia of G. saubinetii that caused blighting of the heads in their 

 experiment, but it is incorrect to suppose that conidia of only this species 

 of Fusarium are found on samples of cereals. They also showed that 

 pure cultures of G. saubinetii from various sources when added to sterile 

 soil in which wheat and oats were sown caused severe rotting of the 

 roots and killing of the young seedlings. 



Schaffnit (8), studying the cause of what is known as "snowmold" 

 in Europe, showed that while Fusarium nivale Ces., the conidial form of 

 Nectria (later Colonectria) graminicola, is the primary cause of "snow- 

 mold" of the cereal crops in Europe, the following organisms are also 

 more or less responsible for this disease: F. culmorum (F. rubiginosum), 



