ANTAGONISM 285 



exhibit mutual aversion at their line of contact, evidenced by kill- 

 ing of the hvphal tips. This property is heritable but is not 

 influenced by sex. Hoppe (1936) noted a similar aversion in the 

 conidial fungus, Diplodia zeae, pathogenic to maize, and the prop- 

 erty remained fixed as shown by repeated inoculation into the 

 living host and reisolation. 



Evidence of antagonism from growth in host tissues. Clear- 

 cut evidence of antagonism between microorganisms when associ- 

 ated within green host plants is lacking or meager. Bamberg 

 (1931) found that several species of unidentified bacteria reduced 

 the virulence of Ustilago zeae and prevented the formation of smut 

 galls when injected into maize coincidentally with smut sporidia 

 or even 3 days later. After smut galls % in. in diameter had de- 

 veloped, injection of bacteria was followed by disintegration of 

 the gall and failure of chlamydospores to form. Johnson (1931) 

 found that certain bacteria produced enzymes capable of dissolv- 

 ing the cell walls of sporidia of several smuts and that others with 

 the same enzymes were unable to attack the sporidia. From these 

 results she concluded that the antagonistic principle was not an 

 enzyme. 



Savastano and Fawcett (1929) inoculated citrus fruits with 

 combinations of various fungi normally associated with decays 

 of such fruit. In some combinations the rate of decay was slower 

 than that produced by the slower-growing component by itself. 

 These investigators conclude that the cause of modification of 

 rate of decay is correlated with specific food requirements of the 

 respective species and with the competition for these foods that 

 must occur. The two common molds, Penicillium italicum and 

 P. digitatum, that attack citrus fruits are antagonistic, P. digitatum 

 being able to grow with greater rapidity and to surround the area 

 decayed by P. italicum. 



Perhaps the best evidence in hand of antagonism between fungi 

 is exhibited by the numerous instances of hyperparasitism familiar 

 to every mycologist. Among the better known are Cicinnobolus 

 cesatii, parasitic on various Ervsiphaceae, Darhica filum on the 

 uredinia and telia of rusts, Tuber cidina maxima on the pycnia and 

 aecia of various blister rusts, including Cronartium ribicola, Myco- 

 gyne pemiciosa on mushrooms, Hypomyces sp. on Russula, Lac- 

 tarius, and other Hymenomycetes, and Sclerotinia fructicola on 

 hypertrophies induced by Taphrina mirabilis. 



