6 TECHNICAL BULLETIN 17 



of 1920. A similar Helminthosporium was isolated from the nodes, 

 sheaths, and blades of the same plants. 



In addition to H. sativum, Alternaria was frequently obtained from 

 blackened kernels and nodes; a pink Fusarium was sometimes found 

 on the base of the stem and roots ; and Helminthosporium teres Sacc. 

 was occasionally isolated from the leaves and stems. 



SELECTION OF HOST VARIETIES 



In all experiments, the effect of the fungus on wheat and barley 

 only was studied. In most cases where barley was tested, both Man- 

 churia (Minn. 105) and Lion (Selection) were used. Manchuria is 

 the barley most commonly grown in Minnesota. It is somewhat re- 

 sistant to H. sativum, as shown by the work of Pammel, King and 

 Bakke (9), of Hayes and Stakman (6), and of Christensen (3). For 

 this reason it was used in the breeding work of Hayes and Stakman. 

 It was crossed with the smooth-awned Lion, which is very susceptible 

 to Helminthosporium, in an attempt to obtain a high yielding, smooth- 

 awned, resistant variety. 



Marquis (Minn. 1239) was used in most of the experiments with 

 wheat. In some cases Haynes Bluestem (Minn. 169) also was used. 



CHECK PLANTS 



Since it is difficult to obtain seed entirely free from Helmintho- 

 sporium, especially in susceptible varieties, it was necessary to treat 

 the seed in order to reduce infection in the check plants to a minimum. 

 Silver nitrate was found to be the most useful disinfectant because 

 the seed coats of both barley and wheat are impermeable to it (10), 

 and the seed can be soaked for! a long time in the solution without 

 being injured. It also is more effective, especially against Helmintho- 

 sporium, than mercuric bichloride. For experimental purposes, the 

 method of seed treatment followed was essentially that recommended 

 by Schroeder (10). The seed was dipped in 50 per cent alcohol to 

 remove the air from the surface, soaked over night in N/ioo silver 

 nitrate solution, dipped in a dilute sodium chloride solution to precipi- 

 tate as insoluble silver chloride the silver nitrate remaining on the 

 surface of the seed, washed thoroly in running tap water, and dried. 

 Such treatment reduced the germination of Lion barley from 90 per 

 cent to 78 per cent, and of Marquis wheat from 99 per cent to 97 

 per cent. 



