Feb. i,i92i Variations in Colletotrichum gloeosporioides 725 



species, Glomerella cingulata. To my knowledge, the perfect stage of 

 Clausen's fungus has not been found. Several of my strains produced 

 the perfect stage when first isolated, and the spores and asci were the 

 same as described for G. cingulata. It is, therefore, the opinion of the 

 writer, which will be presented in the following pages, that Colletotrichum 

 gloeosporioides as found in California is a polymorphic species, composed 

 of many strains. 



STRAINS IN COLLETOTRICHUM GLOEOSPORIOIDES 



In the fall of 19 16 when the writer began work at the Citrus Experi- 

 ment Station, the wish was expressed that he should study Colletotrichum 

 gloeosporioides. The different members of the Division of Plant Pathol- 

 ogy had isolated several cultures of this fungus from different citrus 

 hosts. Some of these differed from each other in their cultural character- 

 istics. It was suggested that these forms might have different regional 

 distribution, or that their differences might be due to the host. Other 

 isolations were made from the various citrus hosts; and these, together 

 with the cultures obtained from the different members of the Division of 

 Plant Pathology, were given laboratory numbers and were always spoken 

 of as strains. In all, 46 cultures were used in the study. Forty-two of 

 these represented all the important citrus districts of southern California, 

 and there was one each from Texas, Florida, Alabama and one kindly 

 furnished by Dr. C. L. Shear. 



CULTURAL CHARACTERISTICS 



The various strains were grown on five different media — corn meal 

 agar, green bean plugs, potato agar, lactose-beef agar and oatmeal 

 agar. Each strain was grown on these five different media for a period of 

 18 months. Transfers were made about every 5 weeks, and a record was 

 kept of the variations in growth occurring in each strain on the various 

 media. While most of the strains exhibited different cultural character- 

 istics on the various media, there were a few whose macroscopic charac- 

 teristics of the mycelium were much the same on all the media. Not 

 only did each strain vary in its growth characters on the different media but 

 some of the strains differed characteristically from each other. Therefore, 

 the variations exhibited by the various strains in their cultural character- 

 istics made it possible to classify them into the following five groups. 



Group I: Mycelium white; spores abundant, salmon-colored in mass. 



Group II : Mycelium grey to greenish black on the various media, very 

 little aerial growth on oat agar; spores abundant, salmon-colored or 

 yellowish in mass. 



Group III: Mycelium gray to black on various media; no spore 

 masses on oat agar. 



Group IV: Mycelium gray to black; spore production so abundant 

 on all media that the surface of the medium is nearly covered by a 

 bacteria-like mass of spores. 



