Chapter 2 

 ISOLATION AND CULTIVATION OF FUNGI 



The isolation and cultivation of fungi in pure culture consti- 

 tute an essential procedure in studies involving their structure, 

 developmental history, pathogenesis, and physiological activities. 

 A student of fungi must appreciate at the outset, however, that, 

 even though pure culture techniques are useful in the enrich- 

 ment of knowledge, the results of such studies of responses and 

 activities in artificial environments always require judicious in- 

 terpretation. The underlying reasons for this fact, which gen- 

 erally are not sufficiently emphasized, are that fungi may be quite 

 abnormal when grown on substrata entirely unlike those en- 

 countered in nature, and of necessity they react abnormally when 

 entirely separated from the associative effects of other organisms. 

 These influences might be expected to be more pronounced 

 among pathogenic species, having restricted host relations, than 

 among saprophilous species. It should also be borne in mind 

 that in nature pure cultures seldom occur and, if they do, are 

 not maintained for appreciable periods. 



Many different procedures have been developed for isolating 

 funo-i in pure culture. The choice of method is conditioned by 

 several factors, among them being the kind of fungus, the stage 

 of development of the fungus, the kind of culture (monosporic 

 or gross) which is desired, the judgment of the investigator, and 

 finally the degree of manual skill, dexterity, and painstaking de- 

 votion to detail which the investigator possesses. In some studies 

 it is essential to secure monosporic cultures. Monosporic isolates, 

 however, may be "half fungi," if the fungus is heterothallic or 

 also if it is hermaphroditic, and at the same time self -incompatible 

 and hence self -sterile. It may be advantageous to make a con- 

 siderable number of isolations, using as sources material obtained 

 from different areas or from different host species, in order prop- 



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