4 Journal of Agricultural Research vol. xx.no. t 



description 



In spite of the extensive literature on this subject, there is no de- 

 tailed description of any of the various phases of the disease. In some 

 discussions of the disease no symptoms are given; in others there is a 

 brief description of only the last stages of infection, or rather, of the 

 final results of infection. Because of this situation it seems necessary 

 to describe the disease in detail, giving special attention to some symp- 

 toms which previously have been overlooked. 



BLIGHTED SEED 



Wheat kernels obtained from heads blighted or partly blighted by 

 Gibberella saubinetii show marked evidence of the effect of the Fusarium 

 attack and can be easily distinguished in a sample of grain, even when 

 only a very small percentage of such kernels are present. Wheat seed 

 from blighted heads exhibits one of three more or less distinct and definite 

 pathological symptoms, depending upon the time of head infection. 



(i) Kernels from heads infected early in their development, possibly 

 during or shortly after the blossoming period, are small in size, being 

 sometimes hardly two-thirds as long as the normal. They are pale 

 greenish gray in color, badly shrunken, not firm, and very light in weight. 

 As a rule, such kernels are never able to germinate. They may be 

 heavily infected or even covered with the mycelium of the fungus if they 

 developed near the point of infection, or they may be perfectly free from 

 any fungus mycelium, if they have developed far above the point of 

 infection where the food supply was cut off. 



(2) Kernels from heads infected two or three weeks after the blos- 

 soming period may attain nearly a normal size, but they usually have 

 a slightly shrunken appearance. They are grayish white or cream- 

 white in color, soft and starchy in texture, and much lighter in weight 

 than the normal kernel. In this case, also, they may be infested and 

 even covered with mycelium, which is especially evident in the groove, 

 or they may be entirely free from mycelium, depending on their position 

 in the head with relation to the point of infection. The percentage of 

 germination of kernels in this class is very low. 



(3) The third class of kernels consists of those which have been infected 

 shortly before or just after the head is ripe. Such kernels differ very 

 slightly from the normal, except that they are partly discolored, pinkish 

 spots being not uncommon on them. While it is true that Gibberella 

 saubinetii is the most common cause of pinkish red coloring on kernels 

 in all three of these classes, it must be remembered that other fungi, 

 Macrosporium and Alternaria for instance, may in some cases cause 

 this coloring of grain. Kernels of this last class usually germinate nor- 

 mally, but before the young plant has reached the surface of the soil, 

 or before it attains any considerable size, it not uncommonly wilts and 



